What follows are some excerpts from a manuscript on the PCC (psychological correlates of consciousness) that I've been working on for a while, which will perhaps never see the light of day. Philosophers, feel free to have a field day with my naive ideas.
Note I'm not sure which of the ideas are mine and which I stole from others. Of the inspirations I remember, two stick out. One, Gregory suggested that qualia function as a 'tag for the present' (see his paper on this
here), and Trehub has also suggested similar ideas in the domain of space (based on his book
The Cognitive Brain).
Note: slightly edited on 1/21/08 after initial posting. I initially expressed some things in a somewhat muddled way, so tried to unmuddle them as best I could.
The Perspectival World Model (PWM) hypothesis is a conjecture about the contents
of consciousness. The core of the PWM hypothesis is explicated in Claim (1):
The contents of consciousness are a model of events that are currently evoking activity in a subject’s
sensory receptors. The model at a given time is called the perspectival
world model, or PWM.
Implicit in (1) is that the PWM is perspectival in both a
spatial and temporal sense.
First, the PWM is spatially perspectival. No matter how hard we try, we cannot see the penny which we know is behind the coffee cup, things behind our back, or the front cover of a book whose spine is facing us. What child who has read comic books hasn’t tried with all his might to see through clothing or engage in other perceptual feats that would violate this limitation on perception? Despite these limitations, bring any of these objects into the right spatial relation to our sensory receptors, so that they activate our retinae for instance, and they can become integrated into the PWM.
Second, the PWM is temporally perspectival because it is a model of what is
presently evoking activity in our sensory receptors. It seems there is a small time window of integration within which sensory inputs can have an effect on the PWM. The prick of a mosquito bite, the bright flash of a camera flash, the experience of my coffee cup on the table, are all representations not of what affected my receptors last week or next year, but of what is happening
now.
It seems that the constructor of the PWM is a quite radical empiricist, building into the model only features that are supported by current direct sensory evidence. While this imposes rather severe limitations on the PWM, it should not seem surprising that organisms would benefit from building a model of what is happening here and now: that is where most of the biological exigencies are in the struggle to reproduce, avoid being eaten, and to acquire food.
The PWM model of consciousness has lots of potential philosophical implications. I'll mention one. I believe it renders the ‘perspectival’ nature of conscious experience nonmysterious. The ‘first-person’ or ‘perspectival’ nature of conscious experience is often taken to be one of its profound properties that is not amenable to “objective, third-person” scientific methods. While at this point in time consciousness is admittedly a mysterious feature of the universe, it is not because of its perspectivalness. Perspectivalness is built into the PWM from the start, and is a perfectly physical spatial and temporal perspectivalness that emerges from a system struggling to model what is causing its sensors to be activated at the present moment in time. To use philosophers’ jargon, the perspectivalness of consciousness is no more mysterious than the perspectivalness that is part of the semantics of indexical expressions such as ‘here’ and ‘now.’
So that is the skeleton of the model (I've left out a discussion of some features of the PWM, such as its limited capacity relative to the rest of the information processing going on in our brains, and whether the PWM is modal, amodal, or multimodal).
I'll now mention some of the most obvious potential concerns and problems with the hypothesis.
1. PWM not sufficient for consciousnessThere seem to be lots of unconscious PWMs in our brains. The human mind carries out a whole host of sensory
and motor tasks using cognitive machinery to which we do not have conscious
access. Examples include our ability to effortlessly dart our eyes to and fro
when confronted with a crowded visual scene, to carve time-varying airborne pressure
waves into sentences, and to solve complicated motor control
problems such as hitting a baseball moving at over 100 mph.
So, what must be added to a brain-model of what is happening here and now to make it conscious? I have lots of ideas, none of which I'm confident about. I touch on them a little bit in numbers 5, 6, and 7 below.
Note that Richard Gregory thinks that qualia tag the present so we don't confuse representations that are memories (e.g., the memory of being stung by a bee) from those that tell us what is happening now. However, there are all sorts of unconcsious representations of what is happening now (e.g., activity in the retina), so he runs into the same problem.
2. What about experiencing the past and future?If qualia tag the here and now, what of imagining things in the past and future? The experiences of such imaginings are likely due to activation of the sensory cortices during such episodes, which then produces a PWM. But why, then, do we not confuse imagined from perceived events? I'm not sure (but see 3 and 7).
3. Hallucinations, dreamsThese are states in which there is nothing in the world corresponding to the model. Consciousness most likely evolved as a mechanism for perceiving events during ordinary waking states, not for use in dreaming
or hallucinations. Dreams and hallucinations seem like an off line use of the PWM machinery caused either by altering the inputs to the PWM-generating mechanism, altering the PWM-generaing mechanism itself, or both.
4. What is the time window?While the PWM tags the present (at least that is the temporal content of the model), what is the time window within which the PWM-building mechanisms integrates information to construct the model? Is it fixed, flexible, does it depend on the sensory modality?
5. Modal, amodal, or multimodal?Seeing a wooden cube and touching a wooden cube are quite different experiences, suggesting that the PWM carries information about which receptors are being activated, i.e., that it is not amodal. But if you touch and look at the cube at the same time, is the information integrated into a unified multimodal representation? Or perhaps, are there multiple conscious PWMs, one for each modality, that "feel" unified because they happen to overlap appropriately in space? I tend to look at the PWM as a spatially integrated multimodal model. The modalities are not merged into one amodal soup: the PWM represents felt and seen cubes differently, at least in the sense that you can differentiate these aspects of the PWM and know the modality to which these aspects belong. See 6.
6. SpaceThe PWM represents the spatial location of events in the world. How do the spatial maps for the modalities relate to one another? Is the unifying PWM an egocentric model that is "ready" for use behaviorally? I.e., the most abstract and unified representation of the spatial layout of things in the world that is still egocentric, but which is most likely to be useful to guide behavior with respect to the world?
For instance, most early sensory representations have a receptor-surface-based frame
of reference. These might need to be converted to a more usable format, one readily convertible to behavior. If I see and hear that there is a tiger in front of me, my actions
should be the same: get my body away from the tiger! I shouldn't move my eyes and hears so I don't perceive the tiger, but move my body to escape.
Perhaps Pete Mandik's theory would help me out here.
Note similar questions that I asked about space could be asked about time. That is a very confusing topic, though.
7. What is the PWM used for?Is it used for planning in the near future, distant future, to help form autobiographical memories, to help us in fine motor control as when sewing or riding a bicycle? My hunch is that we use it for longer-term planning. I see a tiger and plan my escape. But see also number 6: perhaps what is essential is that it is a component of a more general process of converting all these different modalities into an integrated spatial coordinate system that can be used to guide behavior. None of these uses are mutually exclusive: it may be like asking, "What is memory for, helping us find food or find mates?"
8. Nonsensory experiencesThe PWM is supposed to be a model of what is activating our sensory receptors. But what about experiences such as the tip of the tongue phenomenon? Looking for the word 'perseverate' has a distinct qualitative feel, but it isn't clear at all that this is a model of a sensory phenomenon. Perhaps I would have to revise the hypothesis so that the PWM includes models of what is happening in other brain regions, like the brain region looking for the word 'perseverate.' But then the PWM is a misnomer, unless we include in the 'world' other brain states.
On the other hand, why not start a model of the PCC with a model of typical perceptual consciousness? My hunch is that with a detailed such model in place (for which the PWM seems to have fewer problems) it will become more clear how it could be expanded to more difficult cases like hallucination, thinking of the past, and the experience of trying to figure out what that word is for getting caught in a cognitive rut.
I look at 1-7 as "friendly" problems that are all in the spirit of the PWM, and think addressing them would help clarify its structure. Number 8 is less friendly. I can either temporarily classify it as a friendly problem and deal with it the same way I hope to deal with the problems of dreams, hallucinations, and imagining the future. Or I can face it head on, as it may point to a severe weakness in the overall proposal, one whose solution will point to a very different model than the PWM.
