possibly by means of cyclic SWS-REM periods
Throughout the night, sleepers experience many periods of slow-wave sleep and rapid-eye-movement sleep. The authors suggest that this cycle of SWS-REM-SWS-REM throughout the night may importantly contribute to consolidation (the transformation of memories to stable storage).
hippocampal networks
Connections between brain cells (neurons) in the hippocampus.
The hippocampus is a seahorse-shaped structure that is associated with the formation of new memories. Damage to the hippocampus results in an inability to form new memories (like in the movie Memento).
sleep neurophysiology
Brain activity during sleep - for example, sleep spindles.
In contrast, we examined learning-induced changes in long-standing social biases
In contrast to previous work, the authors expand on the existing research by attempting to reduce people's biases. Unlike memories for facts, biases are acquired over a long period of time and are constantly reinforced by people's friends, family, and interpretations of their daily experiences.
Such learning typically does not challenge preexisting knowledge nor compete with daily experiences outside the laboratory
Prior to this study, using sounds or smells to cue memories during sleep has been associated with memories for facts, events, and skills. These types of memories are not contradicted in participants' daily lives.
We found that only SWS × REM sleep duration consistently predicted cueing-specific bias reduction at 1 week relative to baseline
The authors found that the amount of time participants spent in slow-wave sleep and rapid-eye-movement sleep combined was related to how much less biased participants were one week after training.
From this result the authors conclude that sleep in particular was necessary for the bias reduction to last.
rapid-eye-movement (REM) duration
The length of time spent in rapid-eye-movement (REM) sleep (the stage of sleep often associated with dreaming).
slow waves
A pattern of brainwave activity represented by slower, rhythmic activity.
Slow waves occur most often during deep sleep and are thought to play a role in consolidation.
sleep spindles
A pattern of brainwave activity represented by bursts of fast rhythmic activity.
Sleep spindles are not well understood but are thought to help coordinate information transfer between different areas of the brain. They may play a role in transforming memories into more permanent, long-term storage.
When compared with baseline (Fig. 1F), cued biases were weaker after 1 week [t(37) = 2.203, P = 0.034], whereas uncued biases were not [t(37) = 0.524,P = 0.603], although the interaction was not significant (F1,37 = 0.471, P = 0.497).
The authors found that compared to initial bias scores, bias scores one week later for the cued counterbias training were significantly less biased than for the uncued counterbias training.
From this result the authors conclude that without cueing, bias returned to pre-study levels while cueing the training during sleep resulted in a sustained bias reduction one week later.
Implicit biases were measured again after 1 week, revealing that the differential bias reduction endured
The authors found that 1 week after the counterbias training and nap, participants continued to show reduced bias for the training that was cued during sleep. The uncued training, however, showed a significant increase in bias over the week back to baseline-levels.
From this result the authors conclude that cueing the counterbias training during sleep results in a lasting reduction in bias.
electroencephalographic signals
Data obtained from EEG (electroencephalogram).
EEG is a non-invasive method that detects electrical activity (from communicating brain cells) in the brain. Participants wear sensors on their head that detect this activity through the scalp.
Click here for a picture of an EEG cap
The authors used this device to detect when participants were asleep and to measure different sleep characteristics.
Results were quantified by using a conventional scoring procedure
This procedure involved calculating the reaction time (how fast participants pressed the button) for trials where the button participants used to classify trials was stereotype consistent (e.g. same button art words and female faces) and subtracting it from the reaction time for trials where the button participants used to classify trials was inconsistent with the stereotype.
Participants who showed slower reactions when the button was inconsistent with the stereotype demonstrated more implicit bias.
See the supplemental materials for more information.
recruited as two subsamples that allowed for a direct replication
The authors divided the 40 participants into two groups to test whether their results were found in both groups. Finding the effect in both groups makes their results more believable.
systems-level consolidation
Systems-level consolidation specifically refers to the process of memory stabilization that involves multiple brain regions, takes a longer time, and results in more permanent long-term memory (as opposed to synaptic consolidation which occurs more immediately after learning).
Click here for more information on the neurological processes of memory stabilization
procedural
Procedural memories are memories for skills (e.g. riding a bike or hitting a baseball).
When you have learned a skill, you are generally unable to consciously describe the specific knowledge that you've gained.
out-group members
People who are not part of the group being preferred (the in-group). If in one context, the group of individuals being preferred is a group of White individuals, then out-group members would be all other individuals.
In experiments that used a first-person-shooter videogame, both White and Black participants were more likely to shoot Black than White individuals, even when they held a harmless object rather than a gun
In a first-person-shooter videogame participants were instructed to shoot individuals who held a gun and to refrain from shooting individuals who were holding non-gun objects such as wallets or soda cans.
This finding remained even when experimenters increased the number of White individuals holding guns and decreased the number of Black individuals holding guns.
The authors use this source to demonstrate that racial bias affects behavior (in this case the likelihood of incorrectly shooting an unarmed person).
the magnitude of which was associated with time in slow-wave and rapid-eye-movement sleep after training
The more time participants spent in different kinds of sleep (i.e. slow-wave sleep and rapid-eye-movement sleep), the smaller their bias.
This finding suggests that the type of sleep specifically affected the training rather than simply the passage of time or some other factor.
counterstereotype information
Information that goes against the stereotype - in this case information that pairs Black with positive items and women with math and science.
social biases
A tendency to generalize about members of a group or to attribute certain characteristics to one group over another. These preferences and attributions can be conscious or unconscious.
Click here to learn more about how biases have become more subtle in the last century.
We were particularly interested in factors that can influence whether such training procedures produce transient or persistent effects. Because pervasive stereotypes in the media and broader culture could function to regenerate a bias that is momentarily reduced (14), maintaining the benefits of training is crucial for the ultimate usefulness of potential bias-reducing interventions.
Connects to English Language Arts Standards Science & Technical Subjects Grade 11-12 11-12.1: Cite specific textual evidence to support analysis of science and technical texts, attending to important distinctions the author makes and to any gaps or inconsistencies in the account.
Connects to Vision and Change Core Competencies and Disciplinary Practice Competency 6: Ability to understand the relationship between science and society
how much training is needed to make implicit benefits persist for long periods of time and transfer to explicit benefits in interpersonal interactions? To what extent do persistent benefits depend on repeated training, the nature of other waking activities after training, and repeated memory reactivation during sleep?
Connects to Vision and Change Core Competencies and Disciplinary Practice Competency 1: Ability to apply the process of science
within-subject analysis of variance (ANOVA), F1,39= 15.453, P < 0.001, ηp2 = 0.284
Connects to Common Core: Statistics & Probability Model with mathematics
Connects to Common Core: Statistics & Probability Interpret linear models
Connects to Common Core: Statistics & Probability Summarize, represent, and interpret data on two categorical and quantitative variables
For example, documented policing errors have repeatedly shown the potential harm of racial profiling
Connects to Vision and Change Core Competencies and Disciplinary Practice Competency 6: Ability to understand the relationship between science and society
B. Rasch, C. Büchel, S. Gais, J. Born , Odor cues during slow-wave sleep prompt declarative memory consolidation. Science 315, 1426–1429 (2007).
In this study participants were asked to memorize stimuli and were either presented with a smell during the learning process or not. Then during sleep, participants were either re-exposed to the same smell as during learning, a different new smell, or no smell. Participants that were re-exposed to the same smell as during learning had better memory for the items the following morning than either the participants exposed to a new smell or to no smell during sleep.
J. D. Rudoy, J. L. Voss, C. E. Westerberg, K. A. Paller , Strengthening individual memories by reactivating them during sleep. Science 326, 1079 (2009).
In this study participants learned where to place pictures on a grid on the computer screen. While they learned the locations, each picture was also associated with a sound (e.g. a picture of a bell was also associated with a bell sound). Then, while participants took a nap, half of the sounds were replayed while they slept. After the nap, participants had a better memory for the picture locations of the sounds that were played during sleep than the sounds that were not played during sleep.
M. A. Wilson, B. L. McNaughton , Reactivation of hippocampal ensemble memories during sleep. Science 265, 676–679 (1994).
In this a seminal study in the area of sleep and memory. Rats have brain cells called 'place cells' that activate when they are in specific locations in their environment. In a series of experiments these researchers demonstrated that place cells that fired in a specific order as the Rat moved around its environment activated in the same order during sleep.
This was the first evidence that memories may be replayed during sleep after learning.
M. Weisbuch, K. Pauker, N. Ambady , The subtle transmission of race bias via televised nonverbal behavior. Science 326, 1711–1714 (2009).
In this study researchers extracted short clips from 11 popular television shows, muted the clip so no sound was produced, erased the character that was being interacted with, and asked participants to rate how the other characters were interacting with the 'invisible' character. Results showed that invisible White characters were interacted with more positively than invisible Black characters.
These same clips were shown to another group of participants and the results showed that exposure to more racially biased nonverbal clips resulted in more implicit bias.
benefits of this counterbias training can be fragile, subject to reversal when the original stereotypes are again reinforced in typical circumstances, such as through the media
In this study researchers extracted short clips from 11 popular television shows, muted the clip so no sound was produced, erased the character that was being interacted with, and asked participants to rate how the other characters were interacting with the 'invisible' character. Results showed that invisible White characters were interacted with more positively than invisible Black characters.
These same clips were shown to another group of participants and the results showed that exposure to more racially biased nonverbal clips resulted in more implicit bias.
The authors use this study to demonstrate that nonverbal bias cues are prevalent in our environment and can impact participants' implicit bias suggesting that our environment can counteract any training that we might do.
Olsson, J. P. Ebert, M. R. Banaji, E. A. Phelps , The role of social groups in the persistence of learned fear. Science 309, 785–787 (2005).
In this study researchers presented participants with two Black faces and two White faces. One of the Black faces and one of the White faces was paired wit a mild electric shock (painful but not hurtful) such that each time the participants saw one of the two shock-associated faces they received a shock.
The researchers then continued to present the faces but stopped giving the shock and measured the fear response.
The results showed that participants established a fear response to both Black and White shock-associated faces but the fear of the Black shock-associated face persisted while participants stopped fearing the White shock-associated face sooner. When this study was conducted with Black and White participants, for White participants the Black face continued to show a fear response, for Black participants the White face continued to show a fear response.
out-group members can be perceived as threatening, and the fear response to those individuals can resist extinction
In this study researchers presented participants with two Black faces and two White faces. One of the Black faces and one of the White faces was paired wit a mild electric shock (painful but not hurtful) such that each time the participants saw one of the two shock-associated faces they received a shock.
The researchers then continued to present the faces but stopped giving the shock and measured the fear response.
The results showed that participants established a fear response to both Black and White shock-associated faces but the fear of the Black shock-associated face persisted while participants stopped fearing the White shock-associated face sooner. When this study was conducted with Black and White participants, for White participants the Black face continued to show a fear response, for Black participants the White face continued to show a fear response.
The authors use this study to demonstrate that fear of out-group members (members of a group that's not your own) may have a tendency to result in a biological fear reaction that may be particularly difficult to extinguish.
Gawronski, R. Deutsch, S. Mbirkou, B. Seibt, F. Strack , When “Just Say No” is not enough: Affirmation versus negation training and the reduction of automatic stereotype activation. J. Exp. Soc. Psychol. 44, 370–377 (2008).
This study compares two types of counterbias training. In one training. In the first type, participants were supposed to respond "YES" when they saw a counter-stereotype pair (e.g. male and weak or female and strong). In the other type of training participants were supposed to respond "NO" when they saw a stereotypical pair (e.g. male and strong or female and weak).
The results showed that counter-stereotype training (saying yes to counter-stereotypes) DECREASED implicit bias while stereotype negation training (saying no to stereotypical pairs) INCREASED implicit bias.
implicit biases can be reduced by learning about counterstereotype cases
This study compares two types of counterbias training. In one training. In the first type, participants were supposed to respond "YES" when they saw a counter-stereotype pair (e.g. male and weak or female and strong). In the other type of training participants were supposed to respond "NO" when they saw a stereotypical pair (e.g. male and strong or female and weak).
The results showed that counter-stereotype training (saying yes to counter-stereotypes) DECREASED implicit bias while stereotype negation training (saying no to stereotypical pairs) INCREASED implicit bias.
The authors use this study to justify the use of counter-stereotype training in this experiment and the show that previous studies have found it effective.
perceived social norms can prescribe people’s expression of stereotyping and prejudice
In this study, participants rated how appropriate it would be to express prejudice to over 100 different groups (e.g. Black Americans and White Southerners but also liars, child molesters, drunk drivers, and doctors). Then a separate group of participants were asked to rate their personal feelings toward each of the 100 groups.
The researchers found that willingness to express personal prejudice against a group was strongly related with how acceptable it was to express prejudice against that group.
The authors use this source to demonstrate that society tells you you're allowed to say about a person influences what you do say about them.
S. Crandall, A. Eshleman, L. O’Brien , Social norms and the expression and suppression of prejudice: The struggle for internalization. J. Pers. Soc. Psychol. 82, 359–378 (2002).
In this study, participants rated how appropriate it would be to express prejudice to over 100 different groups (e.g. Black Americans and White Southerners but also liars, child molesters, drunk drivers, and doctors). Then a separate group of participants were asked to rate their personal feelings toward each of the 100 groups.
The researchers found that willingness to express personal prejudice against a group was strongly related with how acceptable it was to express prejudice against that group.
Recent findings suggest that memory consolidation during sleep may be essential
The National Sleep Foundation released new recommendations for the amount of sleep people should be getting this year.
Click here to see how much the NSF thinks you should be sleeping
For instance, implicit racial biases decrease investments given to racial out-group members in a trust game
In the trust game, participants were presented with a picture of a face and they had to decide whether to offer the person $10 or not. If the participant gave the person $10, the person received $40 and could either give the participant half (so they each received $20) or could keep it all for themselves. Participants saw 300 faces (100 White, 100 Black, and 100 other race) and made the decision to give $10 or not for each face.
Researchers found that the amount of implicit bias participants had was correlated with how much more likely they were to offer a White person money than a Black person. This was not related to participants' explicit report of racist attitudes.
The authors use this source to support their assertion that implicit attitudes of race are correlated with behavior.
Our preconceptions about other people can influence many types of behavior.
California public defenders are focusing on combating implicit bias in the court system.
A. Nosek, F. L. Smyth, N. Sriram, N. M. Lindner, T. Devos, A. Ayala, Y. Bar-Anan, R. Bergh, H. Cai, K. Gonsalkorale, S. Kesebir, N. Maliszewski, F. Neto, E. Olli, J. Park, K. Schnabel, K. Shiomura, B. T. Tulbure, R. W. Wiers, M. Somogyi, N. Akrami, B. Ekehammar, M. Vianello, M. R. Banaji, A. G. Greenwald , National differences in gender-science stereotypes predict national sex differences in science and math achievement. Proc. Natl. Acad. Sci. U.S.A. 106, 10593–10597 (2009).
In this study more than 500,000 participants completed the gender and academics Implicit Association Test (a test that measures your unconscious associations between different genders (males and females) and different academic areas (liberal arts and sciences).
The researchers found that countries where participants had higher
Nations with higher implicit bias scores (associating males with science and females with liberal arts) had larger differences between males' scores and females' scores on an international standardized 8th grade science test.
D. A. Stanley, P. Sokol-Hessner, M. R. Banaji, E. A. Phelps , Implicit race attitudes predict trustworthiness judgments and economic trust decisions. Proc. Natl. Acad. Sci. U.S.A. 108, 7710–7715 (2011).
In the trust game, participants were presented with a picture of a face and they had to decide whether to offer the person $10 or not. If the participant gave the person $10, the person received $40 and could either give the participant half (so they each received $20) or could keep it all for themselves. Participants saw 300 faces (100 White, 100 Black, and 100 other race) and made the decision to give $10 or not for each face.
Researchers found that the amount of implicit bias participants had was correlated with how much more likely they were to offer a White person money than a Black person. This was not related to participants' explicit report of racist attitudes.
A. Moss-Racusin, J. F. Dovidio, V. L. Brescoll, M. J. Graham, J. Handelsman , Science faculty’s subtle gender biases favor male students. Proc. Natl. Acad. Sci. U.S.A. 109, 16474–16479 (2012).
Over 100 science faculty in research universities across the US were asked to determine a starting salary for and rate the application materials of potential research assistants. There were two versions of each application that were identical except that one had a female name and one had a male name. Each faculty member received one of the two versions for each application.
Faculty members rated the male applications higher and suggested a higher starting salary than the identical female applications.
J. Correll, B. Park, C. M. Judd, B. Wittenbrink, M. S. Sadler, T. Keesee , Across the thin blue line: Police officers and racial bias in the decision to shoot. J. Pers. Soc. Psychol. 92, 1006–1023 (2007).
In a first-person-shooter videogame participants were instructed to shoot individuals that held a gun and to refrain from shooting individuals that were holding non-gun objects such as wallets or soda cans.
This finding remained even when experimenters increased the number of White individuals holding guns and decreased the number of Black individuals holding guns.
cortical networks
Connections in the brain between brain cells (neurons) in the cortex (the surface level, grey-matter of the brain).
catastrophizing
The belief that something is much worse than it actually is.
interpersonal interactions
interactions between people, for example when you have a conversation with someone or work with other people to solve a problem.
olfactory
Smells
auditory
Sounds
SWS × REM sleep duration
A measure that reflects the amount of time participants spent in slow-wave sleep and rapid-eye-movement sleep.
It is calculated by multiplying the number of minutes of SWS by the number of minutes of REM sleep.
Stimulation was discontinued at any sign of arousal from sleep
This procedure is necessary in order to ensure that any effect the authors find is specific to sleep (as opposed to hearing the sound consciously while awake).
Biases were reduced compared with baseline levels (Fig. 1B) [within-subject analysis of variance (ANOVA), F1,39= 15.453, P < 0.001, ηp2 = 0.284]. The mean IAT score was 0.559 at baseline and 0.335 at the prenap test
The authors found a decrease in bias from the beginning of the study to just after the counterbias training.
From this finding, the authors can conclude that their counterbias training had an immediate (before-nap) effect.
This bias reduction did not differ as a function of bias type
From this result the authors can conclude that the bias decrease after training was equally effective for both types of bias training (gender and race).
we administered another task wherein the same two sounds prompted participants to form a corresponding face-word pairing
The purpose of this task is to make the association between the sound and the training stronger.
On each trial participants were presented with a female face, a Black face, a science word and a good word.
If they they heard the gender-associated sound they had to match the female face with the science word. If they heard the race-associated sound they had to match the Black face with the good word.
IAT scores showed that participants held implicit social biases for both gender and race, with both scores significantly greater than zero [mean ± SEM, 0.559 ± 0.044; gender t(39) = 9.076, P < 0.001; race t(39) = 8.388, P < 0.001]
At the beginning of the study, participants showed:
1) a gender bias (preference for associating science words with male faces and art words with female faces)
2) a race bias (preference for associating good words with White faces and bad words with Black faces)
Two unusual frequency-modulated sounds were presented during training
The sounds were played immediately after a correct response. One sound was played for counter-gender bias responses, the other for counter-race bias responses.
For some participants Sound A was played with the gender items and Sound B with the race items, and for other participants Sound B was played with the gender items and Sound A with the race items.
Participants viewed several types of face-word pairing but were required to attend and respond only to pairings that countered the typical bias
Participants were asked to press the spacebar as quickly as possible after seeing a face-word pair that countered the typical bias (e.g. a female face with the word 'science').
Half the pairs countered the typical bias and half were filler trials that participants were not supposed to respond to (female + art, male + science, male + art).
declarative
Declarative memories are memories of facts (e.g. the U.S. Declaration of Independence was signed in 1776) and personal life events (e.g. your 10th birthday).
Declarative memories are generally able to be consciously recalled.
At a broader level, the gender gap in science achievement in a nation is correlated with the level of implicit stereotyping of females as not having an aptitude for science
In this study more than 500,000 participants completed the gender and academics Implicit Association Test (a test that measures your unconscious associations between different genders (males and females) and different academic areas (liberal arts and sciences).
The researchers found that countries where participants had higher
Nations with higher implicit bias scores (associating males with science and females with liberal arts) had larger differences between males' scores and females' scores on an international standardized 8th grade science test.
The authors use this source to support their claim that unconscious gender biases are associated with real-world outcomes.
cognitive
Having to do with mental processes for example memory, language, problem solving, and creativity.
affective
Having to do with emotions
When hiring potential research assistants, both male and female faculty members were more likely to hire male than equally qualified female candidates
Over 100 science faculty in research universities across the US were asked to determine a starting salary for and rate the application materials of potential research assistants. There were two versions of each application that were identical except that one had a female name and one had a male name. Each faculty member received one of the two versions for each application.
Faculty members rated the male applications higher and suggested a higher starting salary than the identical female applications.
The authors use this source to demonstrate that gender bias affects behavior (in this case the likelihood of hiring a research assistant based on an application).
Corresponding bias reductions were fortified in comparison with the social bias not externally reactivated during sleep
The counterstereotype training whose sound was played during sleep was more effective (bias was more reduced) than the training whose sound was not played.
This supports the authors' hypothesis!
memory consolidation
The process by which memories become more stable (less likely to be forgotten). The authors' work is based on previous findings that sleep is particularly important for memory consolidation.
This differential bias reduction was not moderated by bias type
The authors found that cueing reduced bias equally for both gender counterbias training and racial counterbias training.
From this the authors can conclude that the type of training did not deferentially affect bias reduction.
Bias change from prenap to postnap varied with cueing condition as predicted
The authors found that for the counterbias training that was cued (the sound associated with it was played during the nap), the bias was smaller post-nap than pre-nap while for the training that was uncued (the sound wasn't played), the bias was no different post-nap than pre-nap.
From this finding the authors can conclude that the cueing during the nap decreased post-nap bias.
Taking into consideration the role of sleep in memory consolidation, we adapted procedures for (i) reducing implicit social biases and (ii) reactivating this training during sleep.
To design their study, the authors combined counterbias training (discussed in the previous paragraph) with memory reactivation during sleep (discussed in this paragraph) in order to reduce racial and gender biases.
We reactivated counterbias information during sleep using subtle auditory cues that had been associated with counterbias training
While participants were asleep, the experimenters played one of two sounds - either the sound associated with the gender counterbias training or the sound associated with the racial counterbias training. The sounds were played softly so that the participants did not wake up.
implicit association test (IAT)
The IAT is a test that measures your implicit (unconscious) biases. You initially practice classifying items based on one set of two categories (e.g. good words respond with the left hand and bad words respond with your right hand). After a number of trials you then classify another set of two categories (e.g. White faces with the left hand and Black faces with the right hand). Then the categories are paired together (e.g. if you see a good word or a White face respond with the left hand and if you see a bad word or a Black face respond with your right hand). Finally the pairings are switched (e.g. if you see a good word or a Black face respond with the left hand and if you see a bad word or a White face respond with your right hand).
Your score is calculated based on your reaction times for responding to White faces when the same key is used to classify good words than your reaction time for responding to Black faces when the same key is used to classify good words.
racial profiling
The use of race, ethnicity, religion, or national origin to determine on which people law enforcement agencies conduct stops, searches, and other investigative procedures. Racial profiling is based on the false assumption that one race is more likely to commit crimes than another.
rapid-eye-movement sleep
Also known as REM. This period of sleep is when most dreams are thought to occur.
slow-wave sleep
Also known as 'deep sleep.'
implicit
Unconscious, outside of awareness and control
egalitarianism
The idea that all people are equal and deserve equal treatment