For example, there are decades of research that shows that you are more likely to become friends with people who live in your dorm, your apartment building, or your immediate neighborhood than with people who live farther away (Festinger, Schachler, & Back, 1950). It is simply easier to form relationships with people you see often because you have the opportunity to get to know them.

People are motivated to maximize the benefits of social exchanges, or relationships, and minimize the costs. People prefer to have more benefits than costs, or to have nearly equal costs and benefits, but most people are dissatisfied if their social exchanges create more costs than benefits.

Robert Sternberg (1986) proposed that there are three components of love: intimacy, passion, and commitment. These three components form a triangle that defines multiple types of love: this is known as Sternberg’s triangular theory of love. Intimacy is the sharing of details and intimate thoughts and emotions. Passion is the physical attraction—the flame in the fire. Commitment is standing by the person—the “in sickness and health” part of the relationship.

Altruism is people’s desire to help others even if the costs outweigh the benefits of helping. In fact, people acting in altruistic ways may disregard the personal costs associated with helping

ocial traits that people find attractive in potential female mates include warmth, affection, and social skills; in males, the attractive traits include achievement, leadership qualities, and job skills (Regan & Berscheid, 1997). Although humans want mates who are physically attractive, this does not mean that we look for the most attractive person possible

Sexual jealousy is part of male aggression; males endeavor to make sure their mates are not copulating with other males, thus ensuring their own paternity of the female’s offspring. Although aggression provides an obvious evolutionary advantage for men, women also engage in aggression

The experience of bullying can be positive for the bully, who may enjoy a boost to self-esteem. However, there are several negative consequences of bullying for the victim, and also for the bystanders. How do you think bullying negatively impacts adolescents? Being the victim of bullying is associated with decreased mental health, including experiencing anxiety and depression (APA, 2010). Victims of bullying may underperform in schoolwork (Bowen, 2011). Bullying also can result in the victim committing suicide (APA, 2010). How might bullying negatively affect witnesses?

Cyberbullying can take many forms, including harassing a victim by spreading rumors, creating a website defaming the victim, and ignoring, insulting, laughing at, or teasing the victim (Spears et al., 2009). In cyberbullying, it is more common for girls to be the bullies and victims because cyberbullying is nonphysical and is a less direct form of bullying (Hoff & Mitchell, 2009)

A script is a person’s knowledge about the sequence of events expected in a specific setting (Schank & Abelson, 1977). How do you act on the first day of school, when you walk into an elevator, or are at a restaurant? For example, at a restaurant in the United States, if we want the server’s attention, we try to make eye contact. In Brazil, you would make the sound “psst” to get the server’s attention. You can see the cultural differences in scripts

Persuasion is the process of changing our attitude toward something based on some kind of communication. Much of the persuasion we experience comes from outside forces. How do people convince others to change their attitudes, beliefs, and behaviors? What communications do you receive that attempt to persuade you to change your attitudes, beliefs, and behaviors?

Cognitive dissonance is aroused by inconsistent beliefs and behaviors. Believing cigarettes are bad for your health, but smoking cigarettes anyway, can cause cognitive dissonance. To reduce cognitive dissonance, individuals can change their behavior, as in quitting smoking, or change their belief, such as discounting the evidence that smoking is harmful.

When in group settings, we are often influenced by the thoughts, feelings, and behaviors around us. Whether it is due to normative or informational social influence, groups have power to influence individuals. Another phenomenon of group conformity is groupthink. Groupthink is the modification of the opinions of members of a group to align with what they believe is the group consensus (Janis, 1972).

An example of informational social influence may be what to do in an emergency situation. Imagine that you are in a movie theater watching a film and what seems to be smoke comes in the theater from under the emergency exit door. You are not certain that it is smoke—it might be a special effect for the movie, such as a fog machine. When you are uncertain you will tend to look at the behavior of others in the theater. If other people show concern and get up to leave, you are likely to do the same. However, if others seem unconcerned, you are likely to stay put and continue watching the movie.

Social roles are defined by culturally shared knowledge. That is, nearly everyone in a given culture knows what behavior is expected of a person in a given role. For example, what is the social role for a student? If you look around a college classroom you will likely see students engaging in studious behavior, taking notes, listening to the professor, reading the textbook, and sitting quietly at their desks. Of course you may see students deviating from the expected studious behavior such as texting on their phones or using Facebook on their laptops, but in all cases, the students that you observe are attending class—a part of the social role of students.

A social norm is a group’s expectation of what is appropriate and acceptable behavior for its members—how they are supposed to behave and think (Deutsch & Gerard, 1955; Berkowitz, 2004). How are we expected to act? What are we expected to talk about? What are we expected to wear? In our discussion of social roles we noted that colleges have social norms for students’ behavior in the role of student and workplaces have social norms for employees’ behaviors in the role of employee.

Psychologist Leon Festinger (1957) defined cognitive dissonance as psychological discomfort arising from holding two or more inconsistent attitudes, behaviors, or cognitions (thoughts, beliefs, or opinions). Festinger’s theory of cognitive dissonance states that when we experience a conflict in our behaviors, attitudes, or beliefs that runs counter to our positive self-perceptions, we experience psychological discomfort (dissonance). For example, if you believe smoking is bad for your health but you continue to smoke, you experience conflict between your belief and behavior.

ypically, attitudes are favorable or unfavorable: positive or negative (Eagly & Chaiken, 1993). And, they have three components: an affective component (feelings), a behavioral component (the effect of the attitude on behavior), and a cognitive component (belief and knowledge) (Rosenberg & Hovland, 1960).

The military example demonstrates the observation that a difficult initiation into a group influences us to like the group more, due to the justification of effort. We do not want to have wasted time and effort to join a group that we eventually leave

The just-world hypothesis is the belief that people get the outcomes they deserve (Lerner & Miller, 1978). In order to maintain the belief that the world is a fair place, people tend to think that good people experience positive outcomes, and bad people experience negative outcomes (Jost, Banaji, & Nosek, 2004; Jost & Major, 2001). The ability to think of the world as a fair place, where people get what they deserve, allows us to feel that the world is predictable and that we have some control over our life outcomes (Jost et al., 2004; Jost & Major, 2001). For example, if you want to experience positive outcomes, you just need to work hard to get ahead in life.

we might tell ourselves that the other team has more experienced players or that the referees were unfair (external), the other team played at home (unstable), and the cold weather affected our team’s performance (uncontrollable).

According to this definition, the presence of a psychological disorder is signaled by significant disturbances in thoughts, feelings, and behaviors; these disturbances must reflect some kind of dysfunction (biological, psychological, or developmental), must cause significant impairment in one’s life, and must not reflect culturally expected reactions to certain life events.

Hallucinations (seeing or hearing things that are not physically present) in Western societies is a violation of cultural expectations, and a person who reports such inner experiences is readily labeled as psychologically disordered. In other cultures, visions that, for example, pertain to future events may be regarded as normal experiences that are positively valued (Bourguignon, 1970)

Dysfunction occurs when an internal mechanism breaks down and can no longer perform its normal function. But, the presence of a dysfunction by itself does not determine a disorder. The dysfunction must be harmful in that it leads to negative consequences for the individual or for others, as judged by the standards of the individual’s culture

The person who washes his hands 40 times per day and the person who claims to hear the voices of demons exhibit behaviors and inner experiences that most would regard as abnormal: beliefs and behaviors that suggest the existence of a psychological disorder.

person must experience inner states (e.g., thoughts and/or feelings) and exhibit behaviors that are clearly disturbed—that is, unusual, but in a negative, self-defeating way. Often, such disturbances are troubling to those around the individual who experiences them. For example, an individual who is uncontrollably preoccupied by thoughts of germs spends hours each day bathing, has inner experiences, and displays behaviors that most would consider atypical and negative (disturbed) and that would likely be troubling to family members.

We do not use terms such as schizophrenics, depressives, or phobics because they are labels that objectify people who suffer from these conditions, thus promoting biased and disparaging assumptions about them. It is important to remember that a psychological disorder is not what a person is; it is something that a person has—through no fault of his or her own. As is the case with cancer or diabetes, those with psychological disorders suffer debilitating, often painful conditions that are not of their own choosing

whose mothers had schizophrenia were later diagnosed with schizophrenia, compared to none of the 50 control adoptees. Other adoption studies have consistently reported that for adoptees who are later diagnosed with schizophrenia, their biological relatives have a higher risk of schizophrenia than do adoptive relatives (Shih, Belmonte, & Zandi, 2004).

People with schizophrenia also may hold grandiose delusions, beliefs that one holds special power, unique knowledge, or is extremely important. For example, the person who claims to be Jesus Christ, or who claims to have knowledge going back 5,000 years, or who claims to be a great philosopher is experiencing grandiose delusions.

Bipolar and related disorders are a group of disorders in which mania is the defining feature. Mania is a state of extreme elation and agitation. When people experience mania, they may become extremely talkative, behave recklessly, or attempt to take on many tasks simultaneously. The most recognized of these disorders is bipolar disorder.

The traumatic event may act as an unconditioned stimulus that elicits an unconditioned response characterized by extreme fear and anxiety. Cognitive, emotional, physiological, and environmental cues accompanying or related to the event are conditioned stimuli. These traumatic reminders evoke conditioned responses (extreme fear and anxiety) similar to those caused by the event itself (Nader, 2001).

Traumatic events that involve harm by others (e.g., combat, rape, and sexual molestation) carry greater risk than do other traumas (e.g., natural disasters) (Kessler, Sonnega, Bromet, Hughes, & Nelson, 1995). Factors that increase the risk of PTSD include female gender, low socioeconomic status, low intelligence, personal history of mental disorders, history of childhood adversity (abuse or other trauma during childhood), and family history of mental disorders (Brewin et al., 2000).

Hoarding disorder is characterized by persistent difficulty in discarding or parting with objects, regardless of their actual value, often resulting in the accumulation of items that clutter and congest her living area.

obsessions are characterized as persistent, unintentional, and unwanted thoughts and urges that are highly intrusive, unpleasant, and distressing (APA, 2013). Common obsessions include concerns about germs and contamination, doubts (“Did I turn the water off?”), order and symmetry (“I need all the spoons in the tray to be arranged a certain way”)

phobia acquisition is through vicarious learning, such as modeling. For example, a child who observes his cousin react fearfully to spiders may later express the same fears, even though spiders have never presented any danger to him.

While anxiety is unpleasant to most people, it is important to our health, safety, and well-being. Anxiety motivates us to take actions—such as preparing for exams, watching our weight, showing up to work on time—that enable us to avert potential future problems. Anxiety also motivates us to avoid certain things—such as running up debts and engaging in illegal activities—that could lead to future trouble.

Social support appears to work by boosting the immune system, especially among people who are experiencing stress (Uchino, Vaughn, Carlisle, & Birmingham, 2012). In a pioneering study, spouses of cancer patients who reported high levels of social support showed indications of better immune functioning on two out of three immune functioning measures, compared to spouses who were below the median on reported social support (Baron, Cutrona, Hicklin, Russell, & Lubaroff, 1990).

Lazarus and Folkman (1984) distinguished two fundamental kinds of coping: problem-focused coping and emotion-focused coping. In problem-focused coping, one attempts to manage or alter the problem that is causing one to experience stress (i.e., the stressor). Problem-focused coping strategies are similar to strategies used in everyday problem-solving: they typically involve identifying the problem, considering possible solutions, weighing the costs and benefits of these solutions, and then selecting an alternative (Lazarus & Folkman, 1984).

Alarm reaction describes the body’s immediate reaction upon facing a threatening situation or emergency, and it is roughly analogous to the fight-or-flight response described by Cannon. During an alarm reaction, you are alerted to a stressor, and your body alarms you with a cascade of physiological reactions that provide you with the energy to manage the situation

Selye (1974) pointed out that not all stress is harmful. He argued that stress can sometimes be a positive, motivating force that can improve the quality of our lives. This kind of stress, which Selye called eustress (from the Greek eu = “good”), is a good kind of stress associated with positive feelings, optimal health, and performance.

Selye’s definition of stress is response-based in that it conceptualizes stress chiefly in terms of the body’s physiological reaction to any demand that is placed on it. Neither stimulus-based nor response-based definitions provide a complete definition of stress. Many of the physiological reactions that occur when faced with demanding situations (e.g., accelerated heart rate) can also occur in response to things that most people would not consider to be genuinely stressful, such as receiving unanticipated good news: an unexpected promotion or raise.

he Cannon-Bard theory of emotion was developed. According to this view, physiological arousal and emotional experience occur simultaneously, yet independently (Lang, 1994

Strong emotional responses are associated with strong physiological arousal. This has led some to suggest that the signs of physiological arousal, which include increased heart rate, respiration rate, and sweating, might serve as a tool to determine whether someone is telling the truth or not.

From 9–12 weeks, the sex organs begin to differentiate. At about 16 weeks, the fetus is approximately 4.5 inches long. Fingers and toes are fully developed, and fingerprints are visible. By the time the fetus reaches the sixth month of development (24 weeks), it weighs up to 1.4 pounds. Hearing has developed, so the fetus can respond to sounds. The internal organs, such as the lungs, heart, stomach, and intestines, have formed enough that a fetus born prematurely at this point has a chance to survive outside of the mother’s womb.

It seems that once we reach adulthood our problem solving abilities change: As we attempt to solve problems, we tend to think more deeply about many areas of our lives, such as relationships, work, and politics (Labouvie-Vief & Diehl, 1999).

According to Erikson (1963), trust is the basis of our development during infancy (birth to 12 months). Therefore, the primary task of this stage is trust versus mistrust. Infants are dependent upon their caregivers, so caregivers who are responsive and sensitive to their infant’s needs help their baby to develop a sense of trust; their baby will see the world as a safe, predictable place. Unresponsive caregivers who do not meet their baby’s needs can engender feelings of anxiety, fear, and mistrust; their baby may see the world as unpredictable.

Meissner’s disks respond to changes in touch, whereas Merkel’s disks respond to sustained touch. So, if a small insect hops onto our hand, the Meissner’s corpuscles in that part of the skin will respond, but they stop responding if the insect stays still.

some evidence to suggest that dogs can “smell” dangerous changes in blood glucose levels in people with diabetes, and can detect the presence of cancerous tumors (Wells, 2010). Dogs’ extraordinary olfactory abilities are due to having greater numbers and more types of olfactory receptors compared to humans.

How would you feel if you were to face this situation?

However, sensorineural hearing loss is the most common form of hearing loss. Sensorineural hearing loss occurs when neural signals from the cochlea fail to be transmitted to the brain, and can be caused by many factors, such as aging, head or acoustic trauma, infections and diseases (such as measles or mumps), medications, environmental effects such as noise exposure (Figure 5.26), and toxins (such as those found in certain solvents and metals). Some people are born without hearing, which is known as congenital deafness. This could be inherited or due to birth complications, prematurity, or infections during pregnancy. Most states mandate that babies have their hearing tested shortly after birth (Penn State Health, 2023). This increases the likelihood that problems can be corrected within the critical period for the development of hearing, which is important for language development.

Sound coming into the ear hits the nooks and crannies in the pinna at different angles depending on its location (above, below in front or behind us). Thus, each sound has a slightly different mixture of frequencies and amplitudes depending on its location (Grothe et al.,  2010). If we have good hearing in both ears, we can also use binaural cues to help localize a sound. Binaural cues are particularly helpful for letting us know whether something is on our right, left, straight ahead, or directly behind us. When sound comes from the side, it reaches the nearest ear first – thus, we have an interaural timing difference. It is also louder in the nearest ear, which we refer to as an interaural level difference (Figure 5.25). Structures in the brainstem and midbrain (Figure 5.21) are important for determining where a sound originates (Grothe et al., 2010).

Several theories have been proposed to account for our ability to translate frequency into pitch. We’ll discuss two of them here: temporal theory and place theory. The temporal theory of pitch perception suggests that a given hair cell produces action potentials at the same frequency as the sound wave. So, a 200 Hz sound will produce 200 action potentials per second. This seems to work for lower frequencies (up to 4,000 vibrations per second). However, we know that neurons need to have a short rest between producing action potentials so this theory cannot explain how we can detect frequencies of up to 20,000 vibrations per second (Shamma, 2001). The place theory of pitch perception complements the temporal theory and suggests that auditory receptors in different portions of the cochlea are sensitive to sounds of different frequencies (Figure 5.24). More specifically, hair cells in the base of the cochlea respond best to high frequencies and hair cells in the tip of the cochlea respond best to low frequencies (Shamma, 2001). We can say that the cochlea is arranged tonotopically (according to tone). The primary auditory cortex is also arranged tonotopically.

he activation of hair cells is a mechanical process: the physical movement of the hairs on the cell leads to the generation of action potentials (neural impulses) that travel along the auditory nerve to the brain. Auditory information is shuttled to the pons, then the midbrain (inferior colliculus), to the medial geniculate nucleus of the thalamus, and finally to the primary auditory cortex in the temporal lobe of the brain for processing. This information is then passed to other association brain areas (Figure 5.21).

he ear is designed to receive and transmit sound to the receptors deep inside it. It can be separated into three main sections. The outer ear structures include the pinna, which is the visible part of the ear, the auditory canal, and the tympanic membrane or eardrum. The middle ear structures consist of three tiny bones known as the ossicles. The inner ear contains the cochlea, a fluid-filled, snail-shaped structure that contains the sensory receptor cells (hair cells) of the auditory system (Figure 5.20). The vestibular systems is also located in the inner ear, it is involved in balance and movement (the vestibular sense) but not hearing.

Our auditory system converts sound waves, which are changes in air pressure, into meaningful sounds. This translates into our ability to hear the sounds of nature, to appreciate the beauty of music, and to communicate with one another through spoken language. This section will provide an overview of the basic anatomy and function of the auditory system.

A 3-D movie uses the same principle. It is created using specialized cameras equipped with two lenses that are separated by the same distance that we have between our two eyes. This allows for the production of two separate movies—one provides a view for the left eye and one for the right eye. The special glasses you wear allow the two slightly different images projected onto the screen to be seen separately by your left and your right eye, your brain then has to put them together. This can give the illusion that an animal, person, or object is coming right toward you.

ur ability to perceive three-dimensional (3-D) space is known as depth perception. Our depth perception allows us to describe things as being in front, behind, above, below, or to the side of other things. We can also see real objects as three-dimensional (they have height, breadth and depth) rather than being flat, like a phot

So, a cell excited by wavelengths associated with green would be inhibited by wavelengths associated with red, and vice versa. Opponent processing helps to explain why we cannot experience greenish-reds or yellowish-blues as colors. The opponent process theory also explains our experience of negative afterimages. You have probably experienced an afterimage after looking directly at a lightbulb. You still see an image of the lightbulb (albeit of a different color) after you look away. The colors of the afterimage that we see can be predicted by the color pairings identified in the opponent-process theory. If we stare at a red color for a minute and then look at a white background, we will see green. You can test this concept using the flag in Figure 5.12.

The most common color vision deficiency is confusion between reds and greens due to the absence or malfunction of the green or red cone types. This red-green color deficiency affects males more than females (Birch, 2012). Among males, it affects approximately 8% of European Whites, 5% of Asians, 4% of Africans, and less than 2% of indigenous Americans, Australians, and Polynesians (Birch, 2012). Only about 0.4% in females of European Caucasian descent have red-green color deficiency (Birch, 2012). Males are affected more than females because this is a sex-linked recessive genetic trait. Males inherit this gene from their mothers via the X chromosome. The Y chromosome in males is small and so lacks many of the genes that are present on the X chromosome (like the ones associated with color vision). So, if the recessive gene is present on the X chromosome in a male, it will be expressed—giving rise to red-green color deficiency. Typically, females are not affected because they are likely to also have a dominant normal color vision gene on their other X chromosome.

ght is not made of different colors—we perceive color by detecting light of different wavelengths. Short wavelength light is perceived as blue, medium wavelengths as green and long wavelengths as red. By mixing these three primary wavelengths in different combinations we are able to match any color. The trichromatic theory of color vision states that we have three different types of cone, each of which is maximally sensitive to one of the three primary wavelengths

What do you think about sewing a kitten’s eye closed for research? Bear in mind, this research was helpful in preventing blindness and permanent vision damage in children born with eye problems. Would you conduct that research, even if it meant causing some harm to cats? Would you think the same way if you were the parent of a child with vision problems? What if you worked at an animal shelter?

Visual information is sent via the thalamus to the primary visual cortex in the occipital lobe at the back of the brain for initial processing. Visual information is then sent to other parts of the brain (association areas) via two major pathways (see Figure 5. 9). The “what” pathway, which projects to the temporal lobe, is involved in object recognition and identification. While the “where/how” pathway projects to the parietal lobe and is involved with processing the location and movement of an object (Milner & Goodale, 2008; Ungerleider & Haxby, 1994). For example, when you see a red ball rolling down the street, the “what” pathway helps you to know what the object is, and the “where/how” pathway helps you to intercept it and pick it up.

Rods and cones are connected (via interneurons) to retinal ganglion cells. Axons from the retinal ganglion cells converge to form the optic nerves, which exits at the back of each eye. The optic nerves carry visual information from the retina to the brain. There are no receptors where the optic nerve leaves the eye, which results in a blind spot in each eye. We are not consciously aware of our blind spots for two reasons: First, each eye gets a slightly different view of the visual field; therefore, the blind spots do not overlap. Second, even if we are looking with just one eye, our brain fills in what it thinks is in the blind spot so we unaware that information is missing. The optic nerve from each eye merges at a point called the optic chiasm before it reaches the thalamus. As you can see in Figure 5.8, the optic chiasm is an X-shaped structure. Information from the right visual field (from both eyes) is sent to the left side of the brain, and information from the left visual field is sent to the right side of the brain.

The different sensitivities of rods and cones are apparent when we compare our vision in a brightly lit environment to a dark one. Imagine you are at home in the evening. The lights are on and you can see the small print in your textbook without much effort and you can also easily avoid eating the orange candies you dislike from the packet of candy that you are eating.

The eyes work a little like a camera (Figure 5.6). Light passes first through the cornea, then the pupil and lens to reach the receptors at the back of the eye. The cornea is the transparent covering over the iris. It serves as a barrier between the eye and the outside world, and helps to focus the light as it enters the eye. The pupil is the small opening in the iris (colored part of the eye). When it is dark, the pupil dilates (expands) to allow more light to enter the eye. When it is very bright, the pupil will constrict to reduce the amount of light that enters the eye. Pupil size is controlled by the muscles in the iris. The size of the pupil is affected by the autonomic nervous system, it becomes large when we are scared or emotionally aroused (sympathetic NS) and smaller when we are resting and digesting (parasympathetic NS). Figure 5.6. The anatomy of the eye is illustrated in this diagram. The lens is attached to muscles that can change its shape so that we can see objects that are close to us, as well as those that are far away. Ideally, the optics of the eye (cornea and lens) produce a picture of the outside world that is perfectly focused on the retina at the back of the eye. The retina contains specialized photoreceptor cells called rods and cones (Figure 5.7). Cones work best in bright light conditions, they are sensitive to detail (like small letters), and help us to perceive color. At the very center of the retina, there is a tiny area, called the fovea, which has only cones. When we are looking directly at an object, e.g., when reading, we move our eyes so the words fall on the fovea, this allows us to see them better. The rest of the retina is important for our peripheral vision and contains both rods and cones. Rods work well in low light conditions, and while they are unable to detect color and fine detail, they help us to see general shapes in dimly lit environments and to detect movement in our peripheral vision.

The visual system constructs a mental representation of the world around us (Figure 5.5). This helps us to successfully navigate through physical space and interact with other individuals and objects in our environments. This section will provide an overview of the basic anatomy and function of the visual system. In addition, we will explore our ability to perceive color and depth.

ensory experiences during early development are critical for perception. All sensory systems need to be stimulated early in life in order for them to develop normally (Cisneros-Franco et al., 2020). All of our senses are stimulated to some extent when we are still in the womb, with the exception of vision. Hence, when we are born, our visual system is less developed than our other sensory systems. The exact timing of critical periods varies across our senses. However, permanent deficits can arise if normal stimulation does not occur during a critical period. For example, if a newborn has visual problems that prevent them from seeing normally in the first year of their life they have permanent difficulties with face perception for the rest of their lives (Pascalis et al., 2020). Similarly, young children with eye problems often develop a condition called amblyopia (lazy eye), where they are unable to see fine details, such as small letters. Amblyopia is permanent if the eye problem is not corrected before the age of 8 years old. Therefore, it is important to detect and resolve any sensory issues, e.g., eye and ear problems as early as possible (Cisneros-Franco et al., 2020; Pascalis et al., 2020).

motivation can also affect perception. Have you ever been expecting a really important phone call and you keep thinking that you hear the phone ringing, only to discover that it is not? If so, then you have experienced how motivation to detect a meaningful stimulus can shift our ability to discriminate between a true sensory stimulus and background noise.

It is not just visual perception that is affected by cultural factors. Culture affects our perception across all sensory modalities. For example, Japanese participants rated Japanese foods (e.g., soy sauce, fermented soybeans etc.) as more pleasant smelling than German participants who were unfamiliar with them (Ayabe-Kanamura et al., 1998).

The cross-race effect is another example of how visual perception is affected by culture and experience. In general, we are better at recognizing faces of people of our own race, better than those from other races (Young et al., 2012). Most studies looking at the cross-race effect have focused on White participants, however, in one study Lee and Penrod found that participant race determines the extent of the cross-race effect. White participants showed larger cross-race effects than Asian participants.

In general, White people from the USA tend to be more individualistic in their outlook, whereas people from East Asia are more collectivistic and place a greater emphasis on the importance of community. Multiple studies have shown that US participants tend to focus on central elements in a picture or scene—like the globe in Figure 5.3, whereas East Asian participants attend more to context. Therefore, East Asian participants are more likely to notice the background objects as well as the larger objects in the foreground. So, in a change blindness study, participants from the US and East Asia take a similar amount of time to see changes in the large, central objects but US participants are slower to notice changes in the background (Masuda & Nisbett, 2006).

Change blindness is when something changes in the environment (or a picture) and you fail to notice. Like inattentional blindness, change blindness is also very common. It explains why we often fail to notice when someone we see every day gets new glasses or a haircut, or shaves off their facial hair. Psychology experiments often investigate change blindness by alternating two slightly different pictures within a video and measuring how quickly participants spot the difference.

The importance of attention for perception of the environment is demonstrated in a famous study conducted by Daniel Simons and Christopher Chabris (1999). In this study, participants watched a video of two teams of people (dressed in black or white) passing two basketballs among them. Participants were asked to count the number of times the team dressed in white passed the ball. During the video, a person dressed in a black gorilla costume walks among the two teams. You would think that everyone would notice the gorilla, right? Nearly half of the people who watched the video didn’t notice the gorilla at all, despite the fact that it was in plain view for nine seconds. Because participants were so focused on counting the passes, they completely tuned out other visual information. Inattentional blindness is the failure to notice something that is completely visible because the person was actively attending to something else and did not pay attention to other things (Mack & Rock, 1998; Simons & Chabris, 1999).

Attention plays a significant role in determining whether we perceive what is sensed. Imagine you are at a party full of music, chatter, and laughter. You get involved in an interesting conversation with a friend, and you tune out all the background noise.

Our sensations (and perceptions) can change over time. In fact, when sensory stimuli remain relatively constant over prolonged periods of time, our perception of them often changes. This is known as sensory adaptation. Imagine that you have been baking a cake but forget to take it out of the oven and it burns.

Alternatively, top-down processes are generally goal directed, slow, deliberate, effortful, and under your control (Fine & Minnery, 2009; Miller & Cohen, 2001; Miller & D’Esposito, 2005). For instance, if you misplaced your keys, how would you look for them? If you had a yellow key chain, you would probably look for a yellow object of a certain size in specific locations where you might leave your keys. You would not look for yellow on your ceiling fan, because you know keys are unlikely to be there. That act of searching for a certain size of yellowness in some locations and not others, would be top-down—under your control and based on your experience. Even very simple perceptions, such as recognizing an object, are influenced by your expectations, prior experiences, and culture.

Our sensory receptors are constantly collecting information from the environment. However, our interactions with the world are affected by how we interpret that information. Perception refers to the way sensory information is interpreted and consciously experienced

For example, imagine you are in a very dark movie theater. If you receive a text message, it is likely that many people would notice your cell phone light up. However, if you were in a brightly lit arena during a basketball game, very few people would notice. The cell phone brightness does not change, but its noticeability changes dramatically between the two contexts. Ernst Weber described the importance of context on difference threshold in the 1830s, and it has become known as Weber’s law: The difference threshold is a constant fraction of the original stimulus.

The sensitivity of a given sensory system to a particular stimulus can be expressed as an absolute threshold. Absolute threshold refers to the minimum amount of stimulus energy that must be present for the stimulus to be reliably detected. Another way to think about this is by asking how dim can a light be, or how soft can a sound be for us to reliably notice it. The sensitivity of our sensory receptors can be quite amazing. For example, on a clear night, the receptors in the back of the eye can detect a candle flame 1.6 miles away (Silver, 2015). Also, under quiet conditions, the receptor cells of the ear can detect the tick of a clock 20 feet away (Galanter, 1962).

What does it mean to sense something? Our sense organs contain sensory receptors, which are specialized neurons that respond to specific types of information in our physical world. They convert the external information into neural energy and then send this to the brain. These biological processes collectively are known as sensation.

Night terrors are episodes of screaming and feelings of intense panic while asleep (Mahowald & Schenck, 2000). Individuals suffering from night terrors often appear to be awake—they might sit up and open their eyes and seem very frightened, however, attempts to console them are ineffective. Night terrors occur during the NREM phase of sleep and people typically have no memory of them on waking (Provini et al., 2011). Night terrors are common among children (40%), but most grow out of them. Generally, night terrors are not treated unless there is some contributing medical or psychological condition (Mayo Clinic, n.d.).

Surprisingly, narcoleptic episodes are often triggered by states of heightened arousal or stress. The typical episode can last from a minute or two to half an hour. Once awakened from a narcoleptic attack, people report that they feel refreshed (Chokroverty, 2010). Frequent narcoleptic episodes often interfere with a person’s ability to perform their job or complete schoolwork, and in some situations can result in significant harm and injury (e.g., driving a car or operating machinery). There is a genetic component to developing narcolepsy, which may be an auto-immune disease. Narcolepsy with cataplexy is associated with reduced secretion of a chemical called orexin from the hypothalamus. Orexin helps to keep us awake (De la Herrán-Arita & Drucker-Colín, 2012; Han, 2012; National Institute of Neurological Diseases, n.d.). Animal models suggest that orexin agonists might be effective treatment for narcolepsy, but research in humans is still lacking (Pizza et al., 2022).Generally, narcolepsy is treated using non-amphetamine  psychomotor stimulant drugs, or if they fail, amphetamines are used. More recently, histamine agonists have also shown promise as non-addictive alternatives (National Institute of Neurological Diseases, n.d.).

Decades of research on SIDS has led to a number of recommendations for parents to protect their children (Figure 4.14). Infants should be placed on their backs when put down to sleep, and their cribs should not contain any items which pose suffocation or overheating threats, such as blankets, pillows, or padded crib bumpers (cushions that cover the bars of a crib). Similarly, infants should not wear hats or be overly dressed when sleeping to prevent overheating, and people in the child’s household should abstain from smoking in the home. Recommendations like these have helped to dramatically decrease the number of infant deaths from SIDS (DeLuca et al., 2016; Mitchell, 2009; Task Force on Sudden Infant Death Syndrome, 2011).

There are two types of sleep apnea: obstructive sleep apnea and central sleep apnea. Obstructive sleep apnea occurs when an individual’s airway becomes blocked during sleep, and air is prevented from entering the lungs. In central sleep apnea, periods of interrupted breathing are caused by a lack of appropriate signals from the brain (White, 2005).

As part of treatment, the sleeping environment is often modified to make it a safer place for those suffering from RBD (Zangini et al, 2011).

In REM behavior disorder (RBD) there is a muscle paralysis failure. Consequently, individuals with RBD are often physically very active during REM sleep, especially during disturbing dreams. These behaviors vary widely, but they can include kicking, punching, scratching, yelling, and behaving like an animal that has been frightened or attacked.

The defense claimed that Scott Falater had killed his wife in his sleep (Cartwright, 2004; CNN, 1999). They argued that he had a history of regular episodes of sleepwalking as a child, and he had even behaved violently toward his sister once when she tried to prevent him from leaving their home in his pajamas during a sleepwalking episode. However, childhood sleep walking is fairly common. Falater had no history of sleep walking as an adult, nor did he have any apparent anatomical brain anomalies or psychological disorders. In Falater’s case, a jury found him guilty of first degree murder in June of 1999 (CNN, 1999). The expert witness for the prosecution pointed out that sleep walking rarely lasts more than 10-20 minutes and the whole series of events took 45 minutes, also they said it would be unusual for the sleep walker not to be awakened by the screams of his victim. There are a number of murder cases where the sleepwalking defense has been offered, but acquittals since 1990 are very rare. In such cases, sleep scientists are now often called upon to produce physiological evidence of a parasomnia (Broughton et al., 1994; Cartwright, 2004; Mahowald, et al., 2005; Pressman, 2007).

Stick to the same sleep schedule, even on the weekends. Try going to bed and waking up at the same time every day to keep your biological clock in sync so your body gets in the habit of sleeping every night. Avoid stimulating activities for an hour before bed. That includes exercise and bright light from devices, like phones and computers. Exercise daily, but not right before bedtime.  Avoid naps.  Keep your bedroom temperature between 60 and 67 degrees. People sleep better in cooler temperatures. Avoid alcohol, cigarettes, caffeine, and heavy meals before bed. It may feel like alcohol helps you sleep, but it actually disrupts REM sleep and leads to frequent awakenings. Heavy meals may make you sleepy, but they can also lead to frequent awakenings due to gastric distress. If you cannot fall asleep, leave your bed and do something else until you feel tired again. Train your body to associate your bed with sleeping rather than other activities like studying, eating, or watching television shows.

Cognitive-behavioral therapy (CBT) has been shown to be highly effective in treating insomnia (Savard et al., 2005; Williams et al., 2013). CBT is a type of psychotherapy that focuses on cognitive processes and problem behaviors.

insomnia treatment often takes different approaches depending on the cause. Individuals may need to limit their use of stimulant drugs like caffeine or increase their amount of physical exercise during the day

One of the most common sleep disorders is insomnia, which is characterized by difficulty falling or staying asleep. One of the criteria for insomnia involves experiencing these symptoms for at least three nights a week for at least one month (Roth, 2007). People suffering from insomnia often experience increased levels of anxiety about their inability to fall asleep. This can lead to a self-perpetuating cycle where increased anxiety leads to increased arousal, making it even more difficult for them to fall asleep. Chronic insomnia is almost always associated with feeling overtired and may be associated with symptoms of depression.

Dreams often provide messages either for the dreamer or for someone else, which is consistent with the fact that people in collectivistic cultures typically have strong ties with their community. Messages in dreams vary in content, for example, they might give reassurance that the deceased is at peace, or they might provide guidance, approval, or inspiration for their loved ones for their life choices. Alternatively, messages may be prophetic or premonitory in nature. It is also usual for people who value dreams to share them with other members of their community (Comas-Diaz, 2006; Nwoye, 2017; Shafton, 2002).

Allan Hobson, a neuroscientist, is credited for developing the activation-synthesis theory of dreaming. Early versions of this theory proposed that dreams were not the meaning-filled representations of angst proposed by Freud and others, but were rather the result of our brain attempting to make sense of (“synthesize”) the neural activity (“activation”) that was happening during REM sleep.

The sleep and dream researcher, Rosalind Cartwright, however, believes that dreams simply reflect life events that are important to the dreamer. Cartwright’s ideas about dreaming have found empirical support. For example, she and her colleagues published a study in which women going through divorce were asked several times over a five-month period to report the degree to which their former spouses were on their minds. These same women were awakened during REM sleep in order to provide a detailed account of their dream content. There was a significant positive correlation between the degree to which women thought about their former spouses while they were awake and the number of times their former spouses appeared in their dreams (Cartwright et al. 2006).

Freud was not the only Western theorist to focus on the content of dreams. The 20th century Swiss psychiatrist, Carl Jung, believed that dreams allowed us to tap into the collective unconscious. The collective unconscious, as described by Jung, is a theoretical repository of information which he believed was shared by everyone. According to Jung, certain symbols in dreams reflect universal archetypes, and their meanings are similar for all people regardless of culture or location.

By the late 19th century, Austrian psychiatrist Sigmund Freud had become convinced that dreams represented an opportunity to gain access to the unconscious. By analyzing dreams, Freud thought people could increase self-awareness and gain valuable insight to help them deal with the problems they faced in their lives. Freud made distinctions between the manifest and the latent content of dreams. Manifest content is the actual content, or storyline, of a dream.

It is quite possible that sleep serves no single universally adaptive function, and different species have evolved different patterns of sleep in response to their unique evolutionary pressures. While we have discussed the negative outcomes associated with sleep deprivation, it should be pointed out that there are many benefits that are associated with having adequate amounts of sleep.

Evolutionary psychology is a discipline that studies how universal patterns of behavior and cognitive processes have evolved over time as a result of natural selection. One hypothesis from this perspective argues that sleep is essential to restore resources that are expended during the day. Just as bears hibernate in the winter when resources are scarce, perhaps people sleep at night to reduce their energy expenditures. While this is an intuitive explanation of sleep, there is little research to support this explanation. In fact, it has been suggested that there is no reason to think that energetic demands could not be addressed with periods of rest and inactivity while we are awake (Frank, 2006; Rial et al., 2007),

If people are deprived of REM sleep and then allowed to sleep without disturbance, they will spend more time in REM sleep in an effort to recoup the lost time in REM. This is known as REM rebound, and it suggests that REM sleep is also homeostatically regulated. In addition to the role that REM sleep may play in processes related to learning and memory, REM sleep may also be involved in emotional processing and regulation. In such instances, REM rebound may actually be an adaptive response to stress in nondepressed individuals, because it reduces the emotional salience of aversive events that occurred during the day (Suchecki et al., 2012). The hypnogram below (Figure 4.12) shows a person’s passage through the stages of sleep. We cycle through the different stages of sleep through the night, but we have more slow wave sleep in the early parts of the night and more REM sleep later on.

NREM stage 3 sleep is often referred to as deep sleep or slow-wave sleep because this stage is characterized by low frequency (less than 3 Hz), very high amplitude delta waves (Figure 4.10).

As we move into stage 2 sleep

The early portion of stage 1 sleep

As we begin to fall asleep, we enter NREM sleep, and brain wave patterns decrease in frequency and increase in amplitude, indicating that the brain activity is becoming more synchronized and less variable. This increased EEG amplitude indicates that the brain is less busy now

The amplitude is the height (size) of the brain wave. While awake, our EEG is dominated by high frequency brain waves called beta waves (13-30 Hz). Each EEG electrode measures average brain activity from the overlapping peaks and troughs produced by thousands of neurons. When we are awake, the brain is very active and neurons are more variable in the frequencies they produce and so the amplitude of the EEG is low.  As we begin to fall asleep, our brain wave activity changes. Sleep can be divided into two different general phases: rapid eye movement (REM) sleep and non-REM (NREM) sleep.

Sleep is also associated with the secretion and regulation of a number of hormones that are important for growth, immune system function, reproduction, and other metabolic functions. As previously mentioned, the pineal gland releases melatonin during sleep (Figure 4.6), which is involved in the regulation of various biological rhythms and immune system function (Hardeland et al., 2006). During sleep, the pituitary gland secretes both FSH and LH which are important in regulating the reproductive system (Christensen et al., 2012; Sofikitis et al., 2008). The pituitary gland also secretes growth hormone, during sleep, which plays a role in physical growth and maturation, as well as other metabolic processes (Bartke et al., 2013).

Sleep rebound refers to the fact that a sleep-deprived individual will fall asleep more quickly during subsequent opportunities for sleep. Sleep is characterized by distinct stages of brain activity of the brain that can be visualized using electroencephalography (EEG). Sleep-wake cycles are controlled by multiple brain areas acting in conjunction with one another

The Center for Disease Control estimates that over one-third of adults (35%) in the United States do not get enough sleep (defined as less than seven hours per day). Short sleep duration is slightly more common among males (33.4%) than females (32.2%) and is most common among people in the 25 to 44-year-old age group (36.4%).

AGE RECOMMENDED MAY BE APPROPRIATE NOT RECOMMENDED 0–3 months 14–17 hours 11–13 hours 18–19 hours Fewer than 11 hours More than 19 hours 4–11 months 12–15 hours 10–11 hours 16–18 hours Fewer than 10 hours More than 18 hours 1–2 years 11–14 hours 9–10 hours 15–16 hours Fewer than 9 hours More than 16 hours 3–5 years 10–13 hours 8–9 hours 14 hours Fewer than 8 hours More than 14 hours 6–13 years 9–11 hours 7–8 hours 12 hours Fewer than 7 hours More than 12 hours 14–17 years 8–10 hours 7 hours 11 hours Fewer than 7 hours More than 11 hours 18–25 years 7–9 hours 6 hours 10–11 hours Fewer than 6 hours More than 11 hours 26–64 years 7–9 hours 6 hours 10 hours Fewer than 6 hours More than 10 hours ≥65 years 7–8 hours 5–6 hours 9 hours Fewer than 5 hours More than 9 hours

When people have difficulty getting enough sleep due to their work or the demands of day-to-day life, they accumulate a sleep debt. A person with a sleep debt does not get sufficient sleep on a chronic basis. The consequences of sleep debt include decreased levels of alertness and mental efficiency. Interestingly, since the advent of electric light, the amount of sleep that people get has declined.

“If you’ve had a partner who does work regular job 9 to 5 office hours . . . the ability to spend time, good time with them when you’re not feeling absolutely exhausted . . . that would be one of the problems that I’ve encountered.” (West et al., 2009, p. 114)

Individuals who do rotating shift work are also likely to experience disruptions in circadian cycles. Rotating shift work refers to a work schedule that changes from early to late on a daily or weekly basis. For example, a person may work from 7:00 a.m. to 3:00 p.m. on Monday, 3:00 a.m. to 11:00 a.m. on Tuesday, and 11:00 a.m. to 7:00 p.m. on Wednesday. In such instances, the individual’s schedule changes so frequently that it becomes difficult for a normal circadian rhythm to be maintained. This often results in sleeping problems, and it can lead to signs of depression and anxiety. These kinds of schedules are common for individuals working in health care professions and service industries, and they are often associated with persistent feelings of exhaustion and agitation that can make someone more prone to making mistakes on the job (Gold et al., 1992; Presser, 1995).

There are considerable individual differences in our sleep-wake cycles. For instance, some people would say they are morning people, while others would consider themselves to be night owls. These individual differences in circadian patterns of activity are known as a person’s chronotype, and research demonstrates that morning larks and night owls differ with regard to sleep regulation (Taillard et al., 2003). Sleep regulation refers to the brain’s control of switching between sleep and wakefulness, as well as coordinating this cycle with the outside world.

Biological rhythms

This pattern of temperature fluctuation, which repeats every day, is one example of a circadian rhythm. A circadian rhythm is a biological rhythm that takes place over a period of about 24 hours. Our sleep-wake cycle, which is linked to our environment’s natural light-dark cycle, is perhaps the most obvious example of a circadian rhythm, but we also have daily fluctuations in heart rate, blood pressure, blood sugar, and body temperature. Some circadian rhythms play a role in changes in our state of consciousness.

We experience different states of consciousness and different levels of awareness on a regular basis. We can describe consciousness as a continuum that ranges from full awareness to a deep sleep or coma. Sleep is a state marked by relatively low levels of physical activity and reduced sensory awareness that is distinct from periods of rest that occur during wakefulness.

While it is clear that the “fight or flight” response was critical for survival for our ancestors, who lived in a world full of physical threats, many of the highly arousing situations we face in the modern world are more psychological in nature.

his constellation of physiological changes allows the body access to energy reserves and provides heightened sensory capacity so that they would be able to fight off the threat or run away to safety. Once the threat has been resolved, the parasympathetic nervous system would take over and return bodily functions to a relaxed state.

The sympathetic nervous system is often referred to as the fight or flight system, because it is involved in preparing the body for stress-related activities.

e somatic nervous system relays information about our senses (via sensory neurons) to the CNS; and brings information from the CNS to muscles, glands, and organs via motor neurons. Sensory neurons carrying sensory information into the CNS are afferent fibers (afferent means “moving toward”), whereas motor neurons carrying information from the CNS are efferent fibers. A helpful way to remember this is that efferent

The peripheral nervous system is made up of thick bundles of axons, commonly called nerves, which carry messages back and forth between the CNS and the muscles, glands, and organs in the periphery of the body (i.e., everything outside the CNS). The PNS has two major subdivisions: the somatic nervous system and the autonomic nervous system (Figure 3.8).

Psychoactive drugs generally act as agonists or antagonists for a given neurotransmitter system, which is why they can affect our behaviors, thoughts, and feelings.

t the end of every axon, there is a tiny gap called a synapse between the terminal buttons and the next cell, which is often another neuron.

As positively charged potassium ions rapidly leave the neuron, the inside of the cell quickly starts to become less positive (or more negative). This process is called repolarization

The neuron exists in a fluid environment—it is surrounded by extracellular fluid and contains intracellular fluid. The neuronal membrane keeps these two salty fluids separate. Both fluids contain sodium (Na+) and potassium (K+) ions, and other charged molecules. Differences in the overall electrical charge of molecules in the two fluids contribute to a difference in voltage across the membrane, called the membrane potential. When the neuron is resting, the membrane resting potential is about 70 mV and the inside of the neuron is more negatively charged than the outside. In general, ions move quickly across concentration gradients from areas of high concentration to areas of low concentration through the process of osmosis. Na+ is at higher concentrations outside the neuron, so it strongly wants to move into the neuron. K+ on the other hand, is more concentrated inside the neuron, and so wants to move out of the neuron (Figure 3.5). Because the inside of the neuron is slightly negatively charged compared to the outside, this provides an additional drive for Na+ to be drawn into the neuron (opposite electrical charges attract). We call this an electrical gradient. However, there is relatively little ionic movement across the membrane when the neuron is resting. This is because most of the Na+ and K+ gates in the semi-permeable membrane, which regulate the flow of ions, are closed when the neuron is at rest. This results in a high state of tension across the membrane; the Na+ and K+ ions are waiting for the gates to open so they can move through them, and so the neuron is primed and ready for action. For the most part, the Na+ and K+ gates do a good job of staying closed, but a few open and there is a little bit of leakage of Na+ and K+ in the direction described above. To keep the resting potential stable, there is an active sodium-potassium pump, which pumps three sodium ions out of the neuron for every two potassium ions in.

Multiple sclerosis (MS) is an autoimmune disorder that causes degeneration of the myelin sheath on axons throughout the nervous system. This can result in inefficient transmission, and sometimes total loss, of neural information.

Information is then transmitted to the other end of the neuron down a tail-like process called the axon. Information travels through the neuron in the form of electrical energy. At the end of the axon, there are small structures called terminal buttons which contain chemical messengers called neurotransmitters; these allow the neuron to communicate with other cells.

To improve chances for success, it is common for people receiving medications to undergo psychological and/or behavioral therapies as well. Research suggests that combining drug therapy with other forms of therapy tends to be more effective than any one treatment alone for the treatment of depression (Cuijpers, Noma, et al., 2020) and some anxiety disorders like panic disorder and obsessive-compulsive disorder (Cuijpers, Sijbrandij, et al., 2020).

The nervous system is an electro-chemical communication system, which receives and processes information from the outside world, and allows us to react to it. The nervous system is composed of two basic cell types: neurons and glial cells. The neurons (nerve cells) are the central building blocks of the nervous system, whereas various types of glial cells provide support services.

ne remarkable story relating to neuroplasticity is that of Bob Woodruff, a reporter for ABC, who suffered a traumatic brain injury after a bomb exploded next to the vehicle he was in while covering a news story in Iraq. Woodruff was put in a medical coma for 36 days to reduce his brain swelling. However, as a consequence of his injuries, Woodruff experienced many cognitive problems, including difficulties with memory and language. However, over time and with the aid of intensive amounts of cognitive and speech therapy, Woodruff has shown an incredible recovery of function (Fernandez, 2008). Mostly neuroplasticity is helpful. But, in some cases, the changes that occur in the brain in response to injury can cause further problems, such as phantom limb syndrome, where people experience pain in a limb that has been amputated.

In some situations, it is helpful to understand how the brain is processing information without needing information on the actual location of the activity. Electroencephalography (EEG) provides this information by measuring the electrical activity produced by the brain. In EEG recording, electrodes are placed on a person’s head using conductive gel (Figure 3.32a). The signals received by the electrodes are displayed on a computer screen and show how the brain voltage changes over time, with an accuracy within milliseconds (Figure 3.32b). EEG recordings are especially helpful to researchers studying sleep patterns among individuals with sleep disorders and for studies of epilepsy.

In half of the stimuli, the words matched the facial expression, these are called congruent stimuli, and for the half, the words and expressions did not match, these are called incongruent stimuli. In one part of the study, participants were asked to identify the facial expression and in the other part of the study, they identified the word.

In magnetic resonance imaging (MRI), a person lies inside a scanner that generates a strong magnetic field (Figure 3.29a). The hydrogen atoms in the body’s cells align with the magnetic field. Then a radio wave is turned on, which knocks the hydrogen atoms off their alignment, when the radio wave is turned off, the hydrogen atoms emit electromagnetic signals as they return to their original positions. Tissues of different densities give off different signals, which a computer interprets and displays on a monitor giving highly detailed anatomical images of the structures of the brain (Figure 3.29b). MRI provides more detailed images of the brain than CT scans, and does not expose participants to radiation, but it is more expensive.

Positron emission tomography (PET) scans are functional brain scans because they create pictures of the living, active brain (Figure 3.28a and b). An individual receiving a PET scan drinks, inhales or is injected with a mildly radioactive substance, called a tracer.

A computerized tomography (CT or CAT) scan involves taking multiple x-rays of a particular section of a person’s body or brain from different angles (Figure 3.26). The x-rays pass through tissues of different densities at different rates, allowing a computer to construct a detailed structural image (Figure 3.27). A CT scan is useful for identifying the location and size of damage or tumors.

The temporal lobes are located on each side of the head and are associated with hearing, memory, emotion, and language comprehension. The primary auditory cortex, the first cortical area that processes auditory information, is located within the temporal lobe. Wernicke’s area, which is important for speech comprehension, is located nearby. Whereas individuals with damage to Broca’s area have difficulty producing language, those with damage to Wernicke’s area have difficulty understanding language (Figure 3.25). People with Wernicke’s aphasia can pronounce words. However, what they say does not make sense and is often referred to as word salad.

The brain’s parietal lobe is located immediately behind the frontal lobe, and is involved in attentional processes and processing somatosensory information such as touch, temperature, and pain. Each part of your body sends information to a particular area of the primary somatosensory cortex, so it is organized like a map.

It is subdivided into many different regions, including the motor cortex (Figure 3.22a), which is involved in planning and coordinating movement; the prefrontal cortex, which is responsible for higher-level cognitive functioning; and Broca’s area (Figure 3.22b), which is essential for language production. People who suffer damage to Broca’s area have great difficulty producing language of any kind (Broca’s aphasia).

The substantia nigra (Latin for “black substance”) and the ventral tegmental area (VTA) are also located in the midbrain, Figure 3.14). Both regions contain cell bodies that produce the neurotransmitter, dopamine. The substantia nigra and VTA along with other interconnected brain structures are collectively known as the basal ganglia. The basal ganglia are critical for movement, and are also involved in mood, reward, and addiction behaviors (Berridge & Robinson, 1998; Gardner, 2011; George et al., 2012). Degeneration of the substantia nigra and VTA is involved in Parkinson’s disease.

The word pons literally means “bridge,” and as the name suggests, the pons is a crossing point for many axons traveling back and forth to the brain. It also is involved in regulating brain activity during slee

However, if we had to wait for the brain to respond, it would take a lot longer for the action to occur. The information would have to travel up the spinal cord to the brain where it would be processed, and then the brain would send a command down the spinal cord to the motor neuron and then to the muscle.

Clearly, the spinal cord is an important relay station between the brain and the rest of the body. However, the spinal cord is also able to initiate some basic behaviors in direct response to sensory messages, without any input from the brain. These very rapid automatic responses are called reflexes and are mostly protective. They include the actions of moving quickly away from a hot object and blinking your eye(s) when something comes too close to them.

Sensory nerves bring messages into the spinal cord, which are then sent to the brain. The brain also sends messages to the spinal cord, which are conveyed via motor nerves to the muscles, glands, and organs (Figure 3.11b) Figure 3.11a shows the connections between each spinal cord segment and the specific body areas it serves. The cervical segments connect to muscles in the face, head, neck, shoulders, arms and hands, as well as the diaphragm that controls our breathing.

he spinal cord is functionally organized into 31 segments; each segment is encased within one of the vertebrae (bones) of t

In a lab setting, we can also use a technique known as hemi-field presentation that capitalizes on the anatomical arrangement of the visual pathways to present information to each hemisphere of the brain separately (Figure 3.19). If we stare at a center spot on a computer screen – information to the right of the spot (i.e., the right visual field of each eye) goes to the left side of the brain and information on the left of the spot (left visual field) goes to the right side of the brain Figure 3.19). In typical healthy brains, this information is quickly shared across the corpus callosum but in a split-brain patient, the information stays within each hemisphere. Thus, split brain patients provide scientists with a way to study the function of each hemisphere separately. Split-brain studies have shown that for most people, the left hemisphere is responsible for speech production. This finding comes from hemi-field studies where split-brain people are shown different pictures on each side of the screen. If a split brain person looks at a picture with a key in the left visual field (sent to right hemisphere) and a ring in the right visual field (sent to left hemisphere) and are asked what they see, they would say that they only saw a ring. However, if they were asked to draw what they saw with their left hand, which is also controlled by the right hemisphere, they would draw the key (Figure 3.19). Other studies with split brain patients show that the right hemisphere is better at recognizing faces than the left hemisphere, and is more likely to process information holistically rather than in terms of its individual parts. For example, showing a picture like the one by the artist, Arcimboldo, depicted in Figure 3.20, gives rise to different perceptions depending on which visual field it is shown in. If shown in the left visual field (right hemisphere) split brain patients are likely to perceive a face, but if it is shown in the opposite visual field, they are more likely to perceive the individual elements that the face is made from, such as the fruits and the flowers.

Split brain patients

The brain has two halves called hemispheres that are divided by the longitudinal fissure. The two sides of the brain work in concert together, however, each side of the brain is somewhat specialized for some functions.

he structures that we have already discussed in this chapter are housed below the cerebral cortex which is why we refer to them as subcortical structures. They perform more basic functions than the cortex.

In 1953, surgeons performed experimental brain surgery on Henry Gustav Molaison (H. M.). He was a 27-year-old man who been experiencing severe epileptic seizures since he fell off his bicycle as a child. Surgeons removed the hippocampal structures and much of the amygdala from both sides of his brain. After the surgery, H. M’s seizures became much less severe, but he also suffered some unexpected and devastating consequences of the surgery. He was no longer able to form most types of new memories. For example, he was unable to learn new facts. He could not remember new faces, and he was unable to remember anything that someone had said to him for more than about 30 seconds. He was able to learn new motor skills, such as drawing while looking in a mirror, but afterward he had no recollection of learning how to do it. Researchers were fascinated by his experience, and he is considered one of the most famous case studies in medical and psychological history (Hardt, Einarsson, & Nader, 2010; Squire, 2009). His case provided vital insights as to the importance of the hippocampal structures for explicit memories.

The limbic system is involved in processing information relating to both emotion and memory. Interestingly, the sense of smell projects to the limbic system; therefore, not surprisingly, smell can evoke emotional responses in ways that other sensory modalities do not. The limbic system is made up of a number of different structures, including the hippocampal structures, the amygdala, and the hypothalamus (Figure 3.16). The hippocampus is an essential structure for learning and memory. The amygdala is active when experiencing emotion and is important for tying emotional meaning to our memories. The hypothalamus regulates a number of homeostatic processes, including the regulation of body temperature, appetite, and blood pressure. The hypothalamus also serves as an interface between the nervous system and the endocrine system and in the regulation of sexual motivation and behavior.

The hippocampus (and nearby hippocampal-related structures) play an essential role in the consolidation of explicit memories. Hippocampal structure damage leaves us unable to store new episodic memories. One famous patient, known for years as H. M. to protect his identity, had hippocampal structures removed from both hemispheres of his brain when he was 27 years old, in an attempt to help control the epileptic seizures he had been suffering since childhood (Corkin et al., 1997). The surgery stopped the seizures, but he was not able to form new explicit memories for the rest of his life. However, he was able to remember everything from his childhood and up till 2-3 years before the surgery. It is thought that the hippocampal structures play a role in encoding, storing, and retrieving memories. The hippocampal structures are thought to keep a record of the neural circuits that are active in many different parts of the brain during encoding. During retrieval, the hippocampal structures reactivate the same circuitry. Over time, as memories become consolidated, the hippocampal structures are no longer needed to activate the circuits, they become active automatically. This is why H.M. did not lose most of his memories from before the surgery, only the more recent ones. H.M. was able to learn new implicit memories, such as new procedural memories—which shows that these types of memories are governed by other brain areas. For example, he learned to accurately trace the outline of a shape while looking in a mirror (mirror-tracing). He did the activity multiple days in a row and improved over time, however, on each occasion he never remembered doing it previously (Corkin, 1968; Squire, 2009).

The storage of long-term memories (regardless of their type) involves creating and strengthening connections between neurons in the brain. Each thought, feeling, or behavior is associated with a circuit or network of neurons that are activated at the same time. If neurons within the circuit are frequently and repeatedly stimulated, then it becomes easier to reactivate the circuit in the future. This process is known as long-term potentiation (LTP; Lynch, 2004). Long-term potentiation happens gradually. For example, as soon as you start learning a new skill – such as learning to play the guitar— you slowly modify existing neural circuits and create new ones. Each time you practice, you strengthen the connections between the neurons that you are using. The more you practice the guitar, the stronger (more potentiated) the connections become, and the easier it gets. If you practice a lot, the memory can become consolidated, making it relatively permanent, allowing you to play the guitar for the rest of your life. Memory consolidation involves further synaptic changes in multiple parts of the brain (Alberini et al., 2013). Repetition and attention are essential for LTP to occur, otherwise the connections between neurons can weaken and may even disappear. Under some circumstances, this weakening process is quite useful because it allows our brains to discard information that is likely not very important to us because we have not practiced or tried to retrieve it. When we are learning something new, paying close attention and practicing, signals to our brains that something is important.

Loftus and colleagues have conducted several studies where they have used the power of suggestion to implant false autobiographical memories. The researchers used fake materials, which they told the participants had come from their family members. These included fake stories and digitally altered photographs showing their participants in situations that had never occurred, such as meeting Bugs Bunny at Disney Land (Bugs Bunny isn’t a Disney character) or riding in a hot air balloon (Braun et al., 2002; Wade et al., 2002). Loftus has used this research when testifying in court cases to demonstrate the fallibility of memory and its susceptibility to suggestion. Some of these court cases have involved individuals with recovered repressed memories. Repressed memories are a controversial area in psychology. Some psychologists believe that it is possible to bury (repress) deeply traumatic memories, which can be recovered many years later during therapy sessions.  They argue that some children’s experiences were so traumatizing and distressing that they had to lock those memories away in order to lead some semblance of a normal life. They believe that repressed memories can be buried for decades, but can be accurately recalled through hypnosis and guided imagery techniques (Devilly, 2007). Cheit (2007) has suggested that repressing these memories creates psychological distress in adulthood. The Recovered Memory Project was created so that victims of childhood sexual abuse can recall these memories and allow the healing process to begin (Cheit, 2007; Devilly, 2007).

Most memories are somewhat transient, meaning that they tend to fade over time, especially if they are not activated regularly. In 1885, German psychologist, Hermann Ebbinghaus conducted a study to measure the transience of memory. He was the sole participant in this famous study! First, he memorized long lists of meaningless trigrams (TQM, LMX, etc.) Then he measured how many of them he remembered at various intervals of time for a month (Figure 7.12). The curve in Figure 7.12 shows his rate of forgetting and is called the Ebbinghaus forgetting curve (Ebbinghaus, 1885/1964). Its general shape has been replicated many times in studies of LTM. We can see that initially, there is a rapid, steep loss of information—he forgot more than half the trigrams in the first hour! Then the curve begins to level off, so that after a month, a little bit of information is still retained. You may have had similar experiences if you cram for an exam. You remember very little information a month after the exam.

As you know from Chapter 5 when you read about inattentional blindness, we need to pay attention (at least at some level) for information to enter into our conscious thoughts. Otherwise the information is lost. This ensures that we do not waste time processing irrelevant stimuli in our environment. Provided we pay sufficient attention to it, information will make its way into our intermediate memory store. Psychologists use different terms to describe this kind of memory, including short-term memory (STM) and more recently, working memory (WM). Baddeley and Hitch (1974, 2000) proposed that WM is a more accurate description of what happens between sensory and LTM. Working memory describes whatever we are thinking about in a given moment—in other words, what our minds are working on. As you can see in the model in Figure 7.3, information can enter working memory either from LTM (what we already know) or from sensory memory (what is happening in our environment at a given moment).

In the Atkinson-Shiffrin model, information from the environment is processed first by our various sensory systems (vision, hearing, taste, etc.) and this information is held very briefly in sensory memory. Visual sensory memories (commonly referred to as iconic memories) last about 0.5 seconds longer than the actual stimulus. In contrast, auditory sensory memories (echoic memories) last about 3 seconds longer than the actual stimulus. This brief persistence of sensory information in our memory allows us to perceive the world in a continuous and coherent fashion. For example, as we move our eyes from one location to another, we create overlapping sensory memories. The persistence of visual memory can be demonstrated by moving a flashlight or sparkler very quickly to form a shape. For example, if we move our sparkler very quickly in a circular motion, we can often see a circle (see Figure 7.4). This is because the sensory memory of the starting position and all the other intermediate positions of the sparkler are still present by the time we finish drawing the shape. Similarly, sounds stay in our echoic memory for a few seconds allowing us to integrate them with other sounds, such as other syllables in a word, or words in a sentence. Researchers believe that although the duration of sensory memory is brief, it can hold a massive amount of information at one time—in other words, it has a very large capacity.

Western cognitive psychologists have historically viewed memory as a computer-like information processing system (Figure 7.2). We get information “into” our memories via a process called encoding—energy from the outside world is converted by our sense organs into neural energy and is sent to the brain. Thus, our experiences of the world are represented or coded in terms of patterns of neural activity. The information needs to be stored in such a way that we can retrieve it when needed. However, memory does not work like a video recorder; information is modified during each stage of processing—encoding, storage, and retrieval. Therefore, our memories often do not provide a wholly accurate representation of our external world. We will return to this theme when we discuss memory errors later in the chapter.

Today, scientists agree that good research should be ethical in nature and guided by a basic respect for human dignity and safety, and the humane treatment of animals. However historically, there have been multiple studies that were highly unethical, both in medicine and psychology. In later chapters, you will read about the Milgram Study and the Stanford Prison study, two so-called “classical” studies in social psychology that caused considerable distress to the research participants. Modern-day protections for human participants grew from the actions of Peter Buxton, a journalist who exposed an exceptionally long-lasting, highly unethical medical study, called the Tuskegee study in the national press (see below for more details). As a consequence, the National Research Act was passed in 1974, which imposed strict ethical guidelines for research on humans. Modern-day researchers must demonstrate that the research they propose is ethically sound before it can beg