On 2016 Jan 03, Lydia Maniatis commented:

In comments on Yang and Purves (2004) in PP and PMC, I noted that the main claim - that perception of lightness is linked to the frequencies with which "visual patterns" have been encountered by organisms - is not only inconsistent with principles of biological evolution, but also lacks any supporting rationale. Interestingly, Purves, Monson, Sundararajan and Wojtach (2014) give the impression that they are going to provide such a rationale, in a short section of their article titled “Why Stimulus Frequency Predicts Perception and Behavior,” (which I quote in full below). (The article itself is one of several quite similar pitches for the “wholly empirical” account of visual perception that use Yang and Purves (2004) as key empirical reference).

It should be noted, first, that the title of the section is misleading; it represents as fact claims that have not been corroborated. As I have discussed in detail, the methods of Yang and Purves (2004) are too vague, arbitrary, opaque, conceptually problematic and incomplete to allow the investigators to make such claims even for the narrow set of cases that was the focus of that study. Thus, what is missing in the account is both a rationale and evidence. This being the case, the extract below does not explain a fact, but offers a rationale for a (quite odd) hypothesis.

This hypothesis, as summarized by Purves et al (2014), is that “perceptual values assigned by the frequency of occurrence of visual stimuli accord with the reproductive success of the species and individual.” Below I quote their rationalizations, interspersed with comments of my own.

“Missing from this account, however, is why the frequencies of occurrence of visual stimuli sampled in this way predict perception. The reason, we maintain, is that the relative number of times biologically generated patterns are transduced and processed in accumulated experience tracks reproductive success.”

[This is not a reason, it is a repetition of the unjustified claim that responding to stimuli (whether “biologically generated” or not) on the basis of their frequency is adaptive.]

In Fig. 3, for example, the frequencies of occurrence of the patterns at the stage of photoreception have caused the central luminance value to occur more often when in the lower luminance surround than in the higher one, resulting in a steeper slope at that point on the cumulative distribution function.

[There is no credible evidence for this claim (see my criticism of Yang and Purves (2004). In addition, Purves, Morgenstern and Wojtach (2015) have conceded that the sampling assumptions were flawed).]

“If the relative ranking along this function corresponds to the perception of lightness”

[the operative word is “if;” Purves and Yang (2004) did not test samples for their perceptual effects on independent observers]

“then the higher the rank of a target luminance (T) in a given surround relative to another target luminance with the same surround, the lighter the target should appear. Therefore, because the target luminance in a darker surround (Fig. 3, Left) has a higher rank than the same target luminance in a lighter surround (Fig. 3, Right), the former should be seen as lighter than the latter, as it is. Because the frequency of occurrence of patterns is an evolved property”

[this reference to frequency of occurrence of patterns being an evolved property makes no sense at all – the data in Yang and Purves (2004) are described and sampled as luminance values occurring in the environment, as an objective property of the environment outside of the evolving organism]

“—and because these relative rankings along the function correspond to perception”

[again, this “fact” lacks empirical evidence, as samples perceptual effects were not tested]

“—the visually guided behaviors that result will in varying degrees have contributed to reproductive success.”

[This is just a truism – a post hoc assumption that typical behaviors of existing organisms are behaviors that have contributed to survival and reproduction].

“Thus, by aligning the frequencies of occurrence of light patterns over evolutionary time with perceptions of light and dark and the behaviors they elicit, this strategy can explain vision without solving the inverse optics problem.”

[Nothing in the preceding paragraph serves to justify this statement. It doesn't explain, for example, why such a strategy would be adaptive.]

The “explanation” thus rests on 1. Our taking on faith the unrationalized, never-really-tested and, in fact, impossible-to-test hypothesis that frequency of occurrence of loosely defined, arbitrarily sampled “visual patterns” over the evolutionary lifetime of the species tracks both perception and reproductive success, and 2. Overlooking the absurdity and contradiction of calling frequency of occurrence of luminances in the environment, as measured, using instruments, by Yang and Purves (2004) an “evolved property.” Even if we could make sense of the statement that “frequency of occurrence of patterns is an evolved [or “biologically generated” or occurring “at the stage of photoreception”] property, we would still need a. evidence and b. a rationale for such a unique assertion.

In sum, this “explanation” contains neither evidence nor a rationale; it is wholly unempirical.

p.s. The introduction of the idea of "evolved frequencies" seems unique to this article, in which the authors were (unusually) called on to rationalise their frequency hypothesis. In two more recent articles, reference is made to the "frequency of occurrence of image patterns" (Purves, Morgenstern & Wojtach, 2015a) that appear to be defined in the normal way, i.e. as the product of the focussing of "incoming light" which the structure and lens of the eye organise to form a "high-resolution image" (Purves, Morgenstern & Wojtach, 2015b). If we are talking about frequencies of images organised on basis of the straightforward focussing of incoming light rays, in the same way a camera's autofocus would, what aspect of these frequencies is "evolved" or "biologically generated"? And, again, redundantly, what's the theoretical rationale of the supposed frequency-perception link?

On 2016 Jan 03, Lydia Maniatis commented:

In comments on Yang and Purves (2004) in PP and PMC, I noted that the main claim - that perception of lightness is linked to the frequencies with which "visual patterns" have been encountered by organisms - is not only inconsistent with principles of biological evolution, but also lacks any supporting rationale. Interestingly, Purves, Monson, Sundararajan and Wojtach (2014) give the impression that they are going to provide such a rationale, in a short section of their article titled “Why Stimulus Frequency Predicts Perception and Behavior,” (which I quote in full below). (The article itself is one of several quite similar pitches for the “wholly empirical” account of visual perception that use Yang and Purves (2004) as key empirical reference).

It should be noted, first, that the title of the section is misleading; it represents as fact claims that have not been corroborated. As I have discussed in detail, the methods of Yang and Purves (2004) are too vague, arbitrary, opaque, conceptually problematic and incomplete to allow the investigators to make such claims even for the narrow set of cases that was the focus of that study. Thus, what is missing in the account is both a rationale and evidence. This being the case, the extract below does not explain a fact, but offers a rationale for a (quite odd) hypothesis.

This hypothesis, as summarized by Purves et al (2014), is that “perceptual values assigned by the frequency of occurrence of visual stimuli accord with the reproductive success of the species and individual.” Below I quote their rationalizations, interspersed with comments of my own.

“Missing from this account, however, is why the frequencies of occurrence of visual stimuli sampled in this way predict perception. The reason, we maintain, is that the relative number of times biologically generated patterns are transduced and processed in accumulated experience tracks reproductive success.”

[This is not a reason, it is a repetition of the unjustified claim that responding to stimuli (whether “biologically generated” or not) on the basis of their frequency is adaptive.]

In Fig. 3, for example, the frequencies of occurrence of the patterns at the stage of photoreception have caused the central luminance value to occur more often when in the lower luminance surround than in the higher one, resulting in a steeper slope at that point on the cumulative distribution function.

[There is no credible evidence for this claim (see my criticism of Yang and Purves (2004). In addition, Purves, Morgenstern and Wojtach (2015) have conceded that the sampling assumptions were flawed).]

“If the relative ranking along this function corresponds to the perception of lightness”

[the operative word is “if;” Purves and Yang (2004) did not test samples for their perceptual effects on independent observers]

“then the higher the rank of a target luminance (T) in a given surround relative to another target luminance with the same surround, the lighter the target should appear. Therefore, because the target luminance in a darker surround (Fig. 3, Left) has a higher rank than the same target luminance in a lighter surround (Fig. 3, Right), the former should be seen as lighter than the latter, as it is. Because the frequency of occurrence of patterns is an evolved property”

[this reference to frequency of occurrence of patterns being an evolved property makes no sense at all – the data in Yang and Purves (2004) are described and sampled as luminance values occurring in the environment, as an objective property of the environment outside of the evolving organism]

“—and because these relative rankings along the function correspond to perception”

[again, this “fact” lacks empirical evidence, as samples perceptual effects were not tested]

“—the visually guided behaviors that result will in varying degrees have contributed to reproductive success.”

[This is just a truism – a post hoc assumption that typical behaviors of existing organisms are behaviors that have contributed to survival and reproduction].

“Thus, by aligning the frequencies of occurrence of light patterns over evolutionary time with perceptions of light and dark and the behaviors they elicit, this strategy can explain vision without solving the inverse optics problem.”

[Nothing in the preceding paragraph serves to justify this statement. It doesn't explain, for example, why such a strategy would be adaptive.]

The “explanation” thus rests on 1. Our taking on faith the unrationalized, never-really-tested and, in fact, impossible-to-test hypothesis that frequency of occurrence of loosely defined, arbitrarily sampled “visual patterns” over the evolutionary lifetime of the species tracks both perception and reproductive success, and 2. Overlooking the absurdity and contradiction of calling frequency of occurrence of luminances in the environment, as measured, using instruments, by Yang and Purves (2004) an “evolved property.” Even if we could make sense of the statement that “frequency of occurrence of patterns is an evolved [or “biologically generated” or occurring “at the stage of photoreception”] property, we would still need a. evidence and b. a rationale for such a unique assertion.

In sum, this “explanation” contains neither evidence nor a rationale; it is wholly unempirical.

p.s. The introduction of the idea of "evolved frequencies" seems unique to this article, in which the authors were (unusually) called on to rationalise their frequency hypothesis. In two more recent articles, reference is made to the "frequency of occurrence of image patterns" (Purves, Morgenstern & Wojtach, 2015a) that appear to be defined in the normal way, i.e. as the product of the focussing of "incoming light" which the structure and lens of the eye organise to form a "high-resolution image" (Purves, Morgenstern & Wojtach, 2015b). If we are talking about frequencies of images organised on basis of the straightforward focussing of incoming light rays, in the same way a camera's autofocus would, what aspect of these frequencies is "evolved" or "biologically generated"? And, again, redundantly, what's the theoretical rationale of the supposed frequency-perception link?