On 2017 May 01, Lydia Maniatis commented:

Like too many in the vision literature, this article recycles various unviable odds and ends from the theoretical attic. The general discussion begins with this amazing statement: “It is generally accepted that lateral inhibition among orientation-selective units is responsible for the tilt illusion.” The collection of citations mentioned in the subsequent discussion provides absolutely no support for this completely untenable (if somewhat ambiguous) statement, as all they show is that the perception of any element in the visual field is affected by the structure of the surrounding field. Perhaps (no guarantee) the cases cited could superficially be reconciled with the "lateral inhibition" claim; but it crashes and burns in an infinite number of other cases, the perception of orientation being wholly contingent on a sophisticated structural interpretation of the retinal stimulation; and the neurons responsible for this interpretive activity are, of course, the same neurons supposedly acting via dumb (so to speak) local interactions to produce the "tilt illusion."

The claim that neurons act as detectors of orientation, each attuned to a particular value, is equally untenable (as Teller (1984) has pointed out in detail). Again, claims such as : “lateral interactions between these lines, or neurons, can skew the distribution and change the perceived orientation” are blind to the fact that perception does not act from local to global, but is effectively constrained by the whole visual field and the values inherent in the possible organizations of this field, which are infinite and among which it generally "chooses" only one. We don’t see the tilt of the lines composing the drawn Necker cube veridically from a 2D point of view; so if there were “labeled lines” for tilt, as the authors suggest, then these responses cannot directly affect the percept; but direct percepts are what the authors are using to draw their conclusions. Also, an orientation is a feature of a structure; and any structures in perception are constructed, along with their orientation, from point stimulation from photons striking the retina; so this is a case of the visual system supposedly "detecting" features of things that it has itself created.

Similarly: “Known psychophysical features of the tilt illusion … also suggest low-level locus of the tilt illusion. Taken together, V1 is a likely locus for the main site of the tilt illusion.“ The attribution of perceptual experiences to ‘low level’ or peripheral cortical processes was also criticized by Teller (1984) who noted that it implicitly relies on a “nothing mucks it up” proviso, i.e. assuming the low level activity is directly reflected in the percept, without explaining what happens upstream. Again, attributing a perceptual effect such as the perceived tilt of an image to simple interactions in the same V1 neurons that are responsible for observers' perception of e.g. forms of the room, the computer, the investigators, the keypad, etc., is not credible. It would be paradoxical to claim, as Graham (1992) has done, that some percepts are a direct, conscious reflection of low level neural activity, as there would have to be a higher level process deciding that the interpretation of image x should be mediated only by the lower level, and the products shunted directly to consciousness. Such arguments should never be made again.

Similarly: “To summarize, spatial contextual modulations of V1 neurons and their population responses seem to be likely candidates for the neural basis for simultaneous hue contrast.”

The references to “simultaneous contrast mechanisms” is inapt for all the same reasons, i.e. that this is a an effect highly sensitive to global context with sophisticated criteria, and thus cannot be simply segregated theoretically from the processes of perceptual organization in general.

Finally, I don't get this: "No fixation point was provided..." but then "The observers' task was to adjust the orientation of the comparison grating, which was presented on the other side of the fixation point…” Was there or wasn't there?

On 2017 May 01, Lydia Maniatis commented:

Like too many in the vision literature, this article recycles various unviable odds and ends from the theoretical attic. The general discussion begins with this amazing statement: “It is generally accepted that lateral inhibition among orientation-selective units is responsible for the tilt illusion.” The collection of citations mentioned in the subsequent discussion provides absolutely no support for this completely untenable (if somewhat ambiguous) statement, as all they show is that the perception of any element in the visual field is affected by the structure of the surrounding field. Perhaps (no guarantee) the cases cited could superficially be reconciled with the "lateral inhibition" claim; but it crashes and burns in an infinite number of other cases, the perception of orientation being wholly contingent on a sophisticated structural interpretation of the retinal stimulation; and the neurons responsible for this interpretive activity are, of course, the same neurons supposedly acting via dumb (so to speak) local interactions to produce the "tilt illusion."

The claim that neurons act as detectors of orientation, each attuned to a particular value, is equally untenable (as Teller (1984) has pointed out in detail). Again, claims such as : “lateral interactions between these lines, or neurons, can skew the distribution and change the perceived orientation” are blind to the fact that perception does not act from local to global, but is effectively constrained by the whole visual field and the values inherent in the possible organizations of this field, which are infinite and among which it generally "chooses" only one. We don’t see the tilt of the lines composing the drawn Necker cube veridically from a 2D point of view; so if there were “labeled lines” for tilt, as the authors suggest, then these responses cannot directly affect the percept; but direct percepts are what the authors are using to draw their conclusions. Also, an orientation is a feature of a structure; and any structures in perception are constructed, along with their orientation, from point stimulation from photons striking the retina; so this is a case of the visual system supposedly "detecting" features of things that it has itself created.

Similarly: “Known psychophysical features of the tilt illusion … also suggest low-level locus of the tilt illusion. Taken together, V1 is a likely locus for the main site of the tilt illusion.“ The attribution of perceptual experiences to ‘low level’ or peripheral cortical processes was also criticized by Teller (1984) who noted that it implicitly relies on a “nothing mucks it up” proviso, i.e. assuming the low level activity is directly reflected in the percept, without explaining what happens upstream. Again, attributing a perceptual effect such as the perceived tilt of an image to simple interactions in the same V1 neurons that are responsible for observers' perception of e.g. forms of the room, the computer, the investigators, the keypad, etc., is not credible. It would be paradoxical to claim, as Graham (1992) has done, that some percepts are a direct, conscious reflection of low level neural activity, as there would have to be a higher level process deciding that the interpretation of image x should be mediated only by the lower level, and the products shunted directly to consciousness. Such arguments should never be made again.

Similarly: “To summarize, spatial contextual modulations of V1 neurons and their population responses seem to be likely candidates for the neural basis for simultaneous hue contrast.”

The references to “simultaneous contrast mechanisms” is inapt for all the same reasons, i.e. that this is a an effect highly sensitive to global context with sophisticated criteria, and thus cannot be simply segregated theoretically from the processes of perceptual organization in general.

Finally, I don't get this: "No fixation point was provided..." but then "The observers' task was to adjust the orientation of the comparison grating, which was presented on the other side of the fixation point…” Was there or wasn't there?