On 2017 May 07, Lydia Maniatis commented:

The major assumption of this article is unviable. That it appears premised wholy on early results of Hubel and Wiesel should be a clue:

“The primary function of the biological visual system is to identify objects in an environment. To achieve this, given that in the earlier stages of visual processing an input image would be decomposed into fragmented components by neural mechanisms with localized receptive fields and specific tuning characteristics (Hubel & Wiesel, 1962, 1968), the visual system must be able to integrate image components into the percept of a coherent object.”

As I discuss in a comment on a different article (positing “curvature detectors”), the idea that neurons at any level of the nervous system may be described as “local detectors” is unviable:

(From https://pubpeer.com/publications/8B2F3402AFA4F136252567815CB415):

“As simple as it may seem, the notion of “curvature-sensitive-filter,” or more generally the notion of neurons as “detectors” is wholly untenable for a number of reasons, including those discussed by Teller (1984). On neurons as detectors: “Single simple cells in area 17 are often described as being triggered by, or detecting, the presence of bars of light at particular orientations [because,] of the stimulus set that has been tried, an oriented bar of light seems to make the cell fire fastest. But to say that the cell has a special role in encoding the stimulus which makes it fire fastest is to commit the same fallacy as to say that a cone with maximum sensitivity at 570 nm is a 570nm detector. It would seem to make more sense to assume that each perceptual element is coded by a pattern of firing among many neurons, and that each different firing rate of each cortical cell is important to the neural code….To use the concept of a trigger feature appears to be to claim implicitly three things: that for any given cortical cell most of the stimuli in the universe are in the null class…that the later elements which receive inputs from the cell ignore variations in the firing rate of the cell and treat the cell as binary…it is hard to set aside the convictions that all of the possible firing rates of cortical cells play a role in the neural code; and that the use of broader universes of stimuli in physiological experiments would reveal the size and heterogeneity of the equivalence classes of neurons….” (p. 1243) The arguments obviously also apply to the case of “curvature-detectors,” for which any correlations to firing rates have not been ascertained, but have only been “modeled” on the basis of a narrow set of stimuli. If the outlines of our RF shapes and circles were constructed of dots, or radiating rays, or shapes producing illusory contours, would the data look different? How would such results connect with the “curvature filter” based model? Would it make sense to make yet more ad hoc models for these cases? The adoption of a particular type of stimulus by many researchers serves to immunize them from inconvenient results and create the illusion of an at least superficially coherent research program.

Teller also challenges explanations based on firing activity of sets of cells at a peripheral level of the visual system, on the basis that it relies implicitly on a “nothing mucks it up” proviso, ignoring as it does questions of how this pattern is maintained through the system or how it constrains more complete models. Given such gaps, this type of explanation, she notes, amounts to little more than a “remote homunculus theory.”

A more subtle (and too little appreciated) problem with Schmidtmann and Kingdom’s claims is that they are confusing perceptual cause and effect. The “curves” we are talking about are perceived curves, not actual, objectively curved objects. There are no curves in the retinal stimulation. As we well know, the presence of a particular form in perception is not a passive response to the retinal stimulation, which at its inception consists of points of contact with photons, but an active construction of forms based on principles the outlines of which may be discerned by the products of the process. There are many examples of geometrical forms delineated by luminance differences that are not perceived, e.g. the stimuli used by Gottschaldt (in Ellis (1938) A Source Book of Gestalt Psychology ) and demonstrations by Kanizsa (1979, Organization in Vision). So to say that neurons are detecting curve maxima and minima is basically to say that a form that is first constructed by the visual system, on the basis of dynamic feedback and feedforward mechanisms which we are not even close to understanding, are brought to consciousness, and are secondarily inspected and by a set of detectors said to live at some arbitrary level of the process, which signal the conscious observer in some cryptic way. Again, it’s a hall of mirrors. “

In addition, one could note that, given the massive interconnectedness and interaction of the visual system, when Hubel and Wiesel were recording from particular neurons in V1 they were in effect recording from the whole visual process. That is, it is not possible to claim that these recordings were isolating the independent behavior of these particular neurons.

In addition to the premise that neurons in the visual system act as “local linear detectors” another underlying premise that has zero theoretical support is that the conditions, stimuli and data of these experiments are such as to allow them to be used to infer the behavior of such detectors at specific locations of the visual system. Of course, as Graham (1992) has admitted, hundreds of threshold studies “consistent” with the gross over-interpretation of Hubel and Wiesel’s early results (at a time when V1 was thought to be all there was) were generated in the ensuing decades. This is just one of the latest.

As usual in this type of study, the number of observers is very small (3), two are described as naïve but the third is an author, i.e. not naïve. If naivete matters, then why an author/subject?

As usual in this type of study, a “model,” involving untested or false premises and various atheoretical free parameters, is constructed post hoc, narrowly tailored to the specific dataset, stimuli and conditions. Observations on all other stimuli, conditions fall outside its purview.

As is usual in this type of study, we are given very detailed descriptions of stimuli and conditions, but no indication of their theoretical necessity, and how data and interpretation would change if they were even slightly altered. Relatedly it was interesting to note that stimuli were exposed for 167ms, the identical interval used by Wilson and Wilkinson (1998). What is special about this interval?

“It is known that the visual system cannot group two dots of opposite luminance polarities into a dipole [dot pair] (Glass & Switkes, 1976; J. A. Wilson et al., 2004).” I’m sure this isn’t true. Even if they are the only two dots in the visual field, we will see a pair of dots.

The intellectual level of theorizing in this line of research is exemplified by the elevation of the observation that like figures tend to be grouped together in the visual percept (as in the case of the classic Gestalt dot demos) into “similarity theory.” (Casually tacking on the word “theory” to observations of effects is typical in psychology in general.) Similarity isn’t the only factor mediating organization of the visual stimulus.

On 2017 May 07, Lydia Maniatis commented:

The major assumption of this article is unviable. That it appears premised wholy on early results of Hubel and Wiesel should be a clue:

“The primary function of the biological visual system is to identify objects in an environment. To achieve this, given that in the earlier stages of visual processing an input image would be decomposed into fragmented components by neural mechanisms with localized receptive fields and specific tuning characteristics (Hubel & Wiesel, 1962, 1968), the visual system must be able to integrate image components into the percept of a coherent object.”

As I discuss in a comment on a different article (positing “curvature detectors”), the idea that neurons at any level of the nervous system may be described as “local detectors” is unviable:

(From https://pubpeer.com/publications/8B2F3402AFA4F136252567815CB415):

“As simple as it may seem, the notion of “curvature-sensitive-filter,” or more generally the notion of neurons as “detectors” is wholly untenable for a number of reasons, including those discussed by Teller (1984). On neurons as detectors: “Single simple cells in area 17 are often described as being triggered by, or detecting, the presence of bars of light at particular orientations [because,] of the stimulus set that has been tried, an oriented bar of light seems to make the cell fire fastest. But to say that the cell has a special role in encoding the stimulus which makes it fire fastest is to commit the same fallacy as to say that a cone with maximum sensitivity at 570 nm is a 570nm detector. It would seem to make more sense to assume that each perceptual element is coded by a pattern of firing among many neurons, and that each different firing rate of each cortical cell is important to the neural code….To use the concept of a trigger feature appears to be to claim implicitly three things: that for any given cortical cell most of the stimuli in the universe are in the null class…that the later elements which receive inputs from the cell ignore variations in the firing rate of the cell and treat the cell as binary…it is hard to set aside the convictions that all of the possible firing rates of cortical cells play a role in the neural code; and that the use of broader universes of stimuli in physiological experiments would reveal the size and heterogeneity of the equivalence classes of neurons….” (p. 1243) The arguments obviously also apply to the case of “curvature-detectors,” for which any correlations to firing rates have not been ascertained, but have only been “modeled” on the basis of a narrow set of stimuli. If the outlines of our RF shapes and circles were constructed of dots, or radiating rays, or shapes producing illusory contours, would the data look different? How would such results connect with the “curvature filter” based model? Would it make sense to make yet more ad hoc models for these cases? The adoption of a particular type of stimulus by many researchers serves to immunize them from inconvenient results and create the illusion of an at least superficially coherent research program.

Teller also challenges explanations based on firing activity of sets of cells at a peripheral level of the visual system, on the basis that it relies implicitly on a “nothing mucks it up” proviso, ignoring as it does questions of how this pattern is maintained through the system or how it constrains more complete models. Given such gaps, this type of explanation, she notes, amounts to little more than a “remote homunculus theory.”

A more subtle (and too little appreciated) problem with Schmidtmann and Kingdom’s claims is that they are confusing perceptual cause and effect. The “curves” we are talking about are perceived curves, not actual, objectively curved objects. There are no curves in the retinal stimulation. As we well know, the presence of a particular form in perception is not a passive response to the retinal stimulation, which at its inception consists of points of contact with photons, but an active construction of forms based on principles the outlines of which may be discerned by the products of the process. There are many examples of geometrical forms delineated by luminance differences that are not perceived, e.g. the stimuli used by Gottschaldt (in Ellis (1938) A Source Book of Gestalt Psychology ) and demonstrations by Kanizsa (1979, Organization in Vision). So to say that neurons are detecting curve maxima and minima is basically to say that a form that is first constructed by the visual system, on the basis of dynamic feedback and feedforward mechanisms which we are not even close to understanding, are brought to consciousness, and are secondarily inspected and by a set of detectors said to live at some arbitrary level of the process, which signal the conscious observer in some cryptic way. Again, it’s a hall of mirrors. “

In addition, one could note that, given the massive interconnectedness and interaction of the visual system, when Hubel and Wiesel were recording from particular neurons in V1 they were in effect recording from the whole visual process. That is, it is not possible to claim that these recordings were isolating the independent behavior of these particular neurons.

In addition to the premise that neurons in the visual system act as “local linear detectors” another underlying premise that has zero theoretical support is that the conditions, stimuli and data of these experiments are such as to allow them to be used to infer the behavior of such detectors at specific locations of the visual system. Of course, as Graham (1992) has admitted, hundreds of threshold studies “consistent” with the gross over-interpretation of Hubel and Wiesel’s early results (at a time when V1 was thought to be all there was) were generated in the ensuing decades. This is just one of the latest.

As usual in this type of study, the number of observers is very small (3), two are described as naïve but the third is an author, i.e. not naïve. If naivete matters, then why an author/subject?

As usual in this type of study, a “model,” involving untested or false premises and various atheoretical free parameters, is constructed post hoc, narrowly tailored to the specific dataset, stimuli and conditions. Observations on all other stimuli, conditions fall outside its purview.

As is usual in this type of study, we are given very detailed descriptions of stimuli and conditions, but no indication of their theoretical necessity, and how data and interpretation would change if they were even slightly altered. Relatedly it was interesting to note that stimuli were exposed for 167ms, the identical interval used by Wilson and Wilkinson (1998). What is special about this interval?

“It is known that the visual system cannot group two dots of opposite luminance polarities into a dipole [dot pair] (Glass & Switkes, 1976; J. A. Wilson et al., 2004).” I’m sure this isn’t true. Even if they are the only two dots in the visual field, we will see a pair of dots.

The intellectual level of theorizing in this line of research is exemplified by the elevation of the observation that like figures tend to be grouped together in the visual percept (as in the case of the classic Gestalt dot demos) into “similarity theory.” (Casually tacking on the word “theory” to observations of effects is typical in psychology in general.) Similarity isn’t the only factor mediating organization of the visual stimulus.