Archive for the ‘color’ Category

Postscript on Diachronic Discrimination Failure

Monday, April 6th, 2009

This postscript to the Transcending Zombies series is primarily a follow-up to the remarks on Raffman-style nonconceptualism. Would my objection to the Raffman-style case against conceptualism be defeated by an experimental design that tried to better control for possible context effects of the presentations of the colors? The sort of redesign I here have in mind might go as follows. The stimuli presented in each distinct presentation in the diachronic discrimination case would be one of figures 1 and 2.

colors1

figure 1.

colors2
figure 2.

The task put to the subject is to make a “same as before, yes or no?” judgment about colors appearing on the right side of each display. Synchronic discrimination tasks could use just one of figures 1 and 2 and ask, say of figure 1, if the left and right regions contain the same color.

Such an experimental design is aimed at avoiding the accusation that the colors presented in the synchronic and diachronic contexts are colors presented in different contexts and it thus may not be assumed that there is a color-appearance that is constant across contexts. In this new experiment, the color context of the right-hand color in figure 1 is arguably the same as the color context of the left-hand color in figure 2 since figures 1 and 2 are just spatial rotations of each other.

Does such an experimental design help to defeat the conceptualist? One point in favor of the conceptualist is that in the experiments using figures 1 and 2, there may no longer be a failure of diachronic discrimination. The subject, in being presented with figure 1, is in a position to conceptualize the color on the right as the lighter of the two. Further, the subject may re-conceptualized the diachronic task as, in seeing fig 2 after fig 1, judging whether the lighter of the two has changed its relative spatial location.

Raffman’s Rainbow Unraveled

Monday, March 30th, 2009



Colors perceived but not remembered.

Conceptualized content plays a central role in both the Transcending Zombies argument and my Allocentric-Egocentric Interface theory of consciousness. One of the main lines of resistance to such views hinges on an alleged fineness of grain of sensory experience that outstrips conceptual resources. In this and the next post, I suggest that such allegations are overblown. I develop this suggestion by examining a line of thought concerning color experience.

There exist color pairs sufficiently similar to be indiscriminable across a memory delay while sufficiently distinct to be discriminable when presented simultaneously (Perez–Carpinell et al., 1998; Raffman, 1995). So, for example, two paint chips presented side by side will be clearly and correctly distinguished as having distinct colors, but if presented one after the other, the viewer will be uncertain whether they have distinct colors. Though, for simplicity, I’ll just be focusing here on color, the point generalizes to aspects of vision other than color and also to other sensory modalities besides vision. There are thus a wide variety of stimulus pairs that are discriminable in simultaneous presentations but indiscriminable in serial presentations.

As Raffman (1995) argues, if we make certain natural assumptions concerning the relations of concepts to memory, then the existence of such stimulus pairs puts pressure on the suggestion that conceptual contents exhaust the contents of experience. If the conceptualized is to be equated with the remembered and the recognized, then the existence of such stimulus pairs suggests that experience outstrips our concepts. Whatever constitutes the awareness of the chip that is not sufficiently remembered, that awareness fails to count as the application of a concept since that awareness fails to satisfy the re-identifiability criterion on concept possession.

I want to attack Raffman’s argument by calling into question what seems to be one of its key assumptions. The conclusion that conscious experience has non-conceptual content seems to depend on assuming that the colors are present in consciousness in the same way regardless of mode (simultaneous vs serial) of presentation. The assumption seems to be that in every case in which the paint chips are different there must be corresponding elements in consciousness that are different and in every case in which the paint chips are the same there must be corresponding elements in consciousness that are the same.

The assumption works in the context of an argument for nonconceptual contents of consciousness as follows. If I am not able to correctly conceptualize, that is, correctly judge that the second of a pair of serially presented chips is a different color, even though I can distinguish the pair members in simultaneous presentations, then how can this serve as a basis for the conclusion that there is a non-conceptual consciousness of the distinct colors? Such a conclusion would follow if it were further assumed that in spite of the colors of the chips not being available to conceptualization they were available to consciousness. Putting this in terms of qualia, the simultaneously presented and distinguishable chips, chip 1 and chip 2, give rise to corresponding qualia, quale 1 and quale 2. When the chips are presented serially, the subject is unable to correctly judge/conceptualize the difference between the chips, but the chips nonetheless make a corresponding difference in consciousness by triggering, serially this time, quale 1 and quale 2.

(Indeed, in a version of the argument due to Kelly (2001, see especially p. 398, fn. 2), it is experiences, not paint chips (or emulating Kelly’s lingo “shades as the subject experiences them” not “shades that the subject experiences”) that are distinct and serially presented.)

However, such an assumption is questionable. We may begin to appreciate what’s questionable about it by noting that differences in presentation often result in differences in color perception. Context effects are well known in the literature on color perception. In normal lighting conditions, one and the same paint chip may seem gray or bright yellow depending on what else is present in the visual field. And these context effects need not involve a difference in what light arrives at the eye from the paint chip in question. Nor are they explained by interactions between retinal cells. The perceptual effects of context depend on higher levels of the visual processing hierarchy than the retina.

We may model an explanation of the failure to serially discriminate simultaneously discriminable chips as due to different perceptions arising from the same chips presented in different contexts. Presenting a chip by itself on one occasion and with another chip on another occasion is to present the chip in two different contexts, contexts that give rise to differences in the perception of the color of one and the same chip.

It is open, then, for the conceptualist to explain the relevant cases as follows. Serially presented paint chips are experienced/conceptualized simply as e.g., blue regardless of whether they differ in reality with respect to shade. Simultaneously presented paint chips are experienced/conceptualized as one being e.g., a darker shade of blue than the other. Of course, it is in no conflict with the account I am defending in this paper to posit sub-personal and/or unconscious intermediaries that are non-conceptual. So perhaps it is the case that presenting the same color on different occasions or in multiple locations results in the color being present to the sub-personal or unconscious mind as the same, regardless of whether the color is presented in the simultaneous or the serial context. However, what I am keen to deny is that what makes it into consciousness will be the same regardless of simultaneous versus serial context.

Previous Posts:
1. Introducing Transcending Zombies
2. Anti-Skeptical Maneuvers
3. I Know I’m Not a Zombie
4. Some Remarks on Phenomenal Knowledge
5. The Egocentricity of Phenomenal Knowledge
6. The Knowing and the Known
7. My Physical Properties Fix My Conceptualized Contents
8. My Physical Properties Fix My Egocentric Contents
9. TZ & AEI

Phact Check, Heck

Tuesday, December 9th, 2008

How determinate can phacts – phenomenal facts – get? Can they be so determinate as to outstrip introspective access?

Does it make sense that there could be determinate aspects of phenomenology inaccessible to introspection? It strikes me as odd: I would have thought that phenomenology just was whatever is accessible to introspection. I’m curious what others think of this.

A take contrary to my own is due to Richard Heck (2007, pp. 129-133). Paraphrasing, Heck’s claim is as follows.

Whereas it is available to introspection that I believe of both my car and computer that they are gray, I cannot introspect the determinate contents of my perceptual phenomenology concerning the upper left and lower right patches of a 10 x 10 grid, even though my phenomenology has such determinate contents.

Heck doesn’t provide a visual aid, but I thought it would be fun to cook one up. Check out these patches!

untitled-1-copy.jpg

Figure 1. Is it accessible to introspection whether the upper left and lower right patches are of the same determinate shade? Is it a part of your phenomenology that they are?

Reference:
Heck Jr, R. G. (2007). Are There Different Kinds of Content? In B. McLaughlin & J. Cohen (Eds.), Contemporary Debates in Philosophy of Mind (pp. 117-138). Oxford: Blackwell.

Subjective Colors Online

Tuesday, December 11th, 2007

Benham’s Top or Benham’s Disk involves the elicitation of a perception of colors by a rotating stimulus that is itself only black and white. A terrific online demo is available at this link [here]. My own experience is that at relatively high speeds, the inner bands are yellowish and the outer bands are blueish. Reversing the direction of rotation results in the colors switching locations.

Benham's Top

Reddish Green

Sunday, July 22nd, 2007

The following figure is from “REDDISH GREEN: A CHALLENGE FOR MODAL CLAIMS ABOUT PHENOMENAL STRUCTURE” by Martine Nida-Rumelin & Juan Suarez (link to pdf) and reproduces stimuli utilized in experiments in which paradoxical visual experiences were induced, such as experiences of a single color patch being colored reddish green.

reddishgreen3.jpg

Some subjects report “seeing a homogeneous color phenomenally composed of red and green whose components are as clear and as compelling as the red and blue components of a purple.”

The phenomenon is induced by presenting equilluminant colored stripes in images stabilized via use of an eye-tracker. The experiments reported are from Billock et al. which reproduce experiments from Crane and Piantanida.

See:

Billock, V. A., Gleason, G. A., & Tsou, B. H. (2001). “Perception of forbidden colors in retinally stabilized equiluminant images: an indication of softwired cortical color opponency?” J Opt Soc Am A Opt Image Sci Vis, 18(10), 2398-403.

Crane, H. D., & Piantanida, T. P. (1983). “On Seeing Reddish Green and Yellowish Blue.” Science, 221(4615), 1078-1080.

See also my “Hyperbolic Mary

Hyperbolic Mary

Friday, November 17th, 2006

Flow Crash

Originally uploaded by Pete Mandik.

Paul Churchland, in his recent “Chimerical Colors: Some Novel Predictions from Cognitive Neuroscience” (2005), describes very odd color experiences that are predicted by a neural model of chromatic information processing. In brief, the differential fatiguing and recovery of opponent processing cells gives rise to afterimages with subjective hues and saturations that would never be seen on the reflective surfaces of objects. Such “chimerical colors” include shades of yellow exactly as dark as pitch-black and “hyperbolic orange, an orange that is more ‘ostentatiously orange’ than any (non-self-luminous) orange you have ever seen, or ever will see, as the objective color of a physical object” (p. 328). Such odd experiences are predicted by the model that identifies color experiences with states of neural activation in a chromatic processing network. Of course, it’s always open to a dualist to make an ad hoc addition of such experiences to their theory, but no dualistic theory ever predicted them. Further, the sorts of considerations typically relied on to support dualism—appeals to intuitive plausibility and a priori possibility—would have, you’d expect, ruled them out.

Who would have, prior to familiarity with the neural theory, predicted experiences of a yellow as dark as black? One person who would not have thought there was such an experience as pitch-dark yellow is Ludwig Wittgenstein, who once asked “[W]hy is there no such thing as blackish yellow?” (1978, p. 106). I think it safe to say Wittgenstein would be surprised by Churchland’s chimerical colors. At least, I know I was, and I literally grew up reading Churchland. However, to be certain that we have an example of someone who is surprised—for I would like to conduct a thought experiment about them—let us consider someone, call him “Larry”, who has seen yellow and black and in general all the typical colors a normally sighted adult has seen. Suppose that Larry has never had a chimerically colored afterimage such as hyperbolic orange or pitch-dark yellow. Suppose further that Larry is aware of none of the neuroscience that predicts the existence of such experiences. Now, let us compare Larry to Hyperbolic Mary. Like Jackson’s Mary, Hyperbolic Mary knows all of the physical facts about how human color vision works, including the predictions of chimerically colored afterimages. Suppose also, that like Mary toward the end of Jackson’s story, Hyperbolic Mary has been let out of the black and white room and has seen tomatoes, lemons, grass, cloudless skies, and the like. In short, she has had the average run of basic color experiences. Let us stipulate that she has had all the types of color experiences that Larry has had. The crucial similarity between Mary and Larry is that not only have they seen all of the same colors, neither has had chimerically colored afterimages. Neither has experienced hyperbolic orange or pitch-dark yellow. The crucial difference between Larry and Hyperbolic Mary is that only Hyperbolic Mary is in possession of a theory that predicts the existence of hyperbolic orange and pitch-dark yellow. And here’s the crucial question:

Who will be more surprised upon experiencing chimerical colors for the first time, Larry or Hyperbolic Mary?

I think it’s obvious that Larry will be more surprised. I also think this has pretty significant implications for what we are to think the knowledge of what it is like consists in. One thing that knowing what it is like consists in is something that will determine whether one is surprised or not. Fans of Jackson’s Mary must grant this, for they are fond of explicating Jackson’s Mary’s ignorance of what it is like in terms of her alleged surprise at seeing red for the first time. Well, Hyperbolic Mary is less surprised than Larry on seeing chimerical colors for the first time. This shows that she must have more phenomenal knowledge—more knowledge of what it is like to have certain experiences—than did Larry. Mary was able to represent, in introspection, more properties of her experiences than Larry. And her introspective capacity was augmented by her neuroscientific concepts.

References:
Churchland, P. (2005). “Chimerical Colors: Some Novel Predictions from Cognitive Neuroscience.” In: Brook, Andrew and Akins, Kathleen (eds.) Cognition and the Brain: The Philosophy and Neuroscience Movement. Cambridge: Cambridge University Press.

Wittgenstein, L. (1978). Some Remarks on color, ed. G.E.M. Anscombe, Oxford: Blackwell.