Brain Hammer

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.

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.

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“

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.