Reviewer 3
Review for PERCEPTION of: "A gestalt bubble model of the interaction of lightness, brightness, and form perception" by Steven Lehar (ms #2533 LS/PB)
Note on [Author's Responses] in this document.
Independently from its value, I do not think that this article should be published in a PERCEPTION issue dedicated to a topic as specific as the contextual effects on colour perception. In fact, the work deals with that topic, but it deals with many others as well. [Author's Response] Other reasons make me wonder if the article should be published in any issue of PERCEPTION. I think that it consists of two parts of very different value: the thesis that a reification must take place in perception and the perceptual model. The idea of reification is very interesting; as for the model, I admit that probably I failed to understand it fully, but nevertheless I reckon it contains trivial mistakes. Perhaps the author should first write an article explaining in full details the thesis of reification only, since this deserves to be evaluated separately from the model (the latter can be wrong, and the reification idea still be right); the model should be presented, in a modified version, in a second article, since one cannot introduce too many new ideas in a single work.
My comments follow.
MAJOR POINTS
1.
Fig. 1A is a poor version of Adelson's; one does not perceive what the author claims: it is simply untrue that "the two edges appear phenomenally very different". As a matter of fact, "the information about the reflectance of the component tiles of the block and the direction of the illumination source" not only does not "'pop out' pre-attentively from Fig. 1A" (p. 3), but it is not perceived at all (this is easily explainable, since this information is not specified in the stimulus). Adelson used different levels of grey and added a shadow to show the direction of the illuminant. [Author's Response] Moreover the author ascribes to Adelson (1993) (for instance in the abstract) something that Adelson never said, that is that the interaction between "the perceived illumination and the perceived three-dimensional configuration of the perceived object" suggests "a cognitive accompaniment to low level perception": Adelson (1983) maintains that the phenomena he deals with may be ascribed not to low-level mechanisms, but "to more complex mechanisms occurring later in the visual system", and that does not mean COGNITIVE mechanisms.
2.
Fig. 15B shows that the model is wrong. The model predicts that a column of horizontal lines should seem to continue under an occluding surface; but this is absolutely not what is seen when observing a column of horizontal lines, so the model is not isomorphic to phenomenal experience.
3.
"The depth dimension in this representation can be compressed relative to the other dimensions without violating the principle of isomorphism" (p. 18): I do not understand how, since in perceptual experience the depth dimension is not compressed relative to the other dimensions (the contrary should be proved). Once again, the model is not isomorphic to phenomenal experience.
4.
I do not think that the author means that Fig. 18Z can be perceived in three ways, B, C, and D, since in that case the model would describe a phenomenon that does not take place: it is false that when the figure is "viewed as a convex corner the illuminant is seen to the left, whereas when viewed as a concave corner the illuminant is perceived to the right" (p. 21); in fact, even when I perceive a dihedron in A, this looks always as composed of two faces of different COLOUR, and not of two faces differently illuminated. If Fig. 18A depicts a REAL dihedron the model still is wrong: in "Mach's dihedron" (where shadows are visible) the illusory inversion of the dihedron does not change the phenomenal direction of the illuminant, but the phenomenal COLOUR of the dihedron's faces. Perhaps the phenomenon described by the author would take place if Fig. 18A were seen through a reduction screen, but the author should first state it, and then verify it.
5.
Many assertions are totally gratuitous. For example, consider the author's interpretation of the phenomenon depicted in Fig. 21: the figure does not justify what the author claims. He must at least add a control figure where all the solids have a white lateral face: if the effect were due to the cause suggested by the author, it should not be seen in such a figure. I did draw such a figure, and, in my opinion, the effect is not different from the one in Fig. 21, so very probably the author's explanation of the phenomenon is wrong. I think that Fig. 21 should be eliminated.
It is very questionable, too, that in Fig. 10A "the lines... appear to pull the white surface of the page into depth" (p. 13): I do not see anything of the sort.
6.
Some statements are puzzling. For instance, what does it mean "...or whether reification is a subjective manifestation without neurophysiological counterpart" (p. 4)? Does the author think that some aspects of perception do not have a neurophysiological counterpart? This point should be changed or made clear, no matter what the author's opinion is; in fact, statements of that kind are not easily found in current scientific literature. [Author's Response] Moreover, the meaning of "...reconstruct a representation of the phenomenal world from the evidence provided by the senses" (p. 9) is unclear. It is better to say "construct the phenomenal world ...", or perhaps "reconstruct the world ...".
The author cannot speak of "the nature of the subjective experience of the percept" (p. 28), since the percept is a subjective experience itself.
7.
Koehler (THE PLACE OF VALUE IN A WORLD OF FACTS 1938) takes into consideration the following criticism to the principle of isomorphism: it is easy to abstract from psychological facts their structural characteristics and then describe these characteristics twice, first in psychological terms and then in a little more physiological terms; but this is only a verbal solution, that shifts the problem of the phenomenal experience without solving it. Koehler was able to escape this criticism by proposing a theory (later confuted) that made testable predictions about the nature of the cortical processes underlying phenomenal experience; but Lehar proposes "to restrict ourselves to perceptual modelling, as opposed to neural modelling..." (p. 29): so I am not sure that he can escape the criticism mentioned above.
My doubts increase when I read, for instance, that the author acknowledges that it "remains to be shown whether such dynamics are definable in principle to achieve those results" (p. 18); so we are left only with a verbal and graphical description of what is perceived: does this not mean that the model is only an illusory solution? P. 28: "If the model accurately reflects the nature of the subjective experience of the percept, and offers a quantitative isomorphic representation which corresponds to the subjective experience, then the model is unassailable as a perceptual model, even if its neurophysiological correlate remains to be identified"; I agree: such a model would be unassailable, because it would be an exact copy of the perceptual world, but one wonders what its utility would be. (For the principle of isomorphism it would be better to refer to the book by Koelher mentioned above. Its chapter 6 contains Koehler's most exhaustive exposition of the principle.)
OTHER POINTS
1.
The quotations within the paper are done incorrectly. Only the first author of the article is given, even when the article has more than an author! In this case, the name of the first author should be followed by the expression "et al".
2.
The concept of "relaxation" (p. 2) should be defined, as the concept of "resonant feedback", which is abruptly introduced at p. 10, without explaining what it means.
3.
"This however would represent a violation of the principle of isomorphism" (p. 5), and "This is in contrast with the Gestalt view of perception" (p. 5): these are meant to be criticisms, but they need not be in themselves, as the author never explained why a theory is necessarily wrong if in contrast with the principle of isomorphism. In other words, the author never explains why he thinks that the principle of isomorphism is NECESSARY (and not simply useful).
4.
The work can be fruitfully and easily shortened. For instance, I would cut off sections 1.5 and 2.2. [Author's Response] Besides, the author repeats often that he is offering only a sketch, and not a fully developed model; it is enough to say it, clearly, once or twice. [Author's Response] Fig. 11 and the comment to it can be eliminated, because the inverse optics problem is well known. [Author's Response]
5.
On p. 9 it is said that the retinal image is not at the lowest hierarchical level along the abstraction/reification dimension. It is apparent that here "low" means something different from what it means in the previous part of the article. This should be made clear.
6.
The prediction depicted in Fig. 14B is interesting. Why does the author not test it?
7.
On p. 18 the author says that "This configuration offers less praegnanz, ..."; but he has not clearly explained before why the Gestaltist concept of "praegnanz" is relevant for his model.
8.
P. 25: "... alternative percept of four separate pieces as shown in Fig. 22D". The pieces are three, not four.
It is clear that the ideas are extremely clever, but it is also clear that the author has a theoretical, more than an experimental inclination. This is not a criticism, of course, but the author must be aware that a referee with a strong experimental mentality can be very annoyed by the kind of errors that this work contains, and end up rejecting an article that has other good points; that may seem unfair to the author, but it happens, and I think he should keep this factor in due account if he wants to see his work published. Fig. 21, for example, and the comment to it, can give the bad impression that the author does not feel the need to test the suggestions of his imagination. Figs. 1A and 15B suggest that the author is indifferent to plain facts. I would also urge the author to take care of details, such as the incomplete quotations, that perhaps he considers unworthy of his attention when proposing a new theory of perception, but that are important, even though of no scientific relevance at all, because the referees can found them irritating.