My view has been that the phenomenal visual scene can be
likened to a stack of qualia or phenomenal properties, all simultaneously
experienced or bound together in such a way that it is often difficult to see the
bound parts as distinct from one another, although they are distinguishable in
principle. The root of this stack is the set of phenomenal properties that I
believe are most often identified with ‘qualia’, i.e. properties that have
scalar magnitudes or intensities. Brightness and darkness, color, contrast, and
then at a slightly higher order, orientation, scale, direction, speed. These
are familiar as physical objects of study either in the psychophysical field of
spatial vision, or as determinants of sensitivity in the neurophysiology of the
first few synapses of the initial retinocortical pathway for visual encoding.
But they are not the only phenomenal properties of visual scenes, and in fact
they are not the properties of scenes that we spend the most of our ordinary visual
time analyzing. Instead, we spend most of our visual effort attending to more
fuzzily inferred properties of the scene: identities, utilities, depths,
valences, affordances. These are the properties of a scene that are immediately
apparent to us, but they are the ones that require the most inference: the
shape and meaning of a word; not so much its contrast or color, which we can
easily adapt to and forget, although they remain in our phenomenal
consciousness. I am reminded what Foucault said regarding the multiple layers
of a calligram: “As a sign, the letter permits us to fix words; as line, it
lets us give shape to things.” All these things are simultaneously present and
part of the seen scene, but we tend to attend selectively to certain levels.
I think it is clear from this conception of the phenomenal
scene that indicating the presence of phenomenal properties, i.e. that something is present in consciousness,
requires the presence of the higher level inferences, but not necessarily of
the lower level ‘root’. I can daydream or close my eyes and continue to
experience visual phenomena, although they are indistinct and insubstantial,
and I can tell you about what I experienced, and then we can argue over whether
or not visual imagery constitute visual phenomena. However, if all I have is
the spatial scene, but I am unable to make any inferences about it, then I
cannot report anything about it – reporting presumes context, or cause, or
object, and these all require higher level inferences. Or rather, perhaps I
could report, but my reports would be nearly meaningless, not least because
objective meaning is tied to subjective meaning, which is what we have removed
in this example. My reports would, at best, maybe with some minimal inferences,
allow me to transmit information about the perceptual magnitude of local, ‘low-level’
features. I would then be performing in a psychophysics experiment, and you
would probably be using signal detection theory to interpret my responses.
Norma Graham noted the strange convenience of this situation more than 20 years
ago, when she noted, “It is (or we can hope it is) as if the simplicity of the
experimental situation has made all the higher level stages practically
transparent.”