Wednesday, 19 June 2013

Imagining Itself (part V: Sea Snails and Homunculi)

Whilst it may still be relatively unclear as to the detail of what exactly occurs on a cognitive level as we imagine, perceive or remember, it is widely accepted amongst cognitive scientists and philosophers that memory, perception and imagination are closely related processes.

In his Nobel (2000) prize winning studies of the neurobiology of sea snails, Eric Kandel found that repeated adverse stimuli trigger similar patterns of neuronal activity. Reinforcement led these constellations of activity (“neural pathways”) to become increasingly focused and stable, through protein synthesis, in what is believed to be an elementary form of learning. Some theorists go so far as to claim that this is a form of memory whilst others remain unconvinced that such changes, that we also observe in the skin's response to ultra-violet light, for example, constitute a form of memory.  

Richard Gregory, a prominent British neuropsychologist estimates that human perception may comprise as much as 90% memory. In order to back up this claim Gregory points to the fact that 80% of the nerve fibers to the visual cortex originate from regions of the brain associated with memory functions whereas only 20% issue from the retina.

In the 1970’s Cornell University psychologist, Ulric Neisser put forward the widely acclaimed but implausible notion that perception – of which he considered imagination to be a closely related component - is an evolved form of anticipation in which perceptions are formed as the result of preparations to see, hear, feel etc. For Neisser the perceptual apparatus is led, through the contribution of memories, into an expectation so vivid that it becomes a cognitive substitute for reality. According to Neisser, perception is thus a constructive process in which an internal map or “schema”, as he called it, constantly loops through anticipation, exploration and modification in an interweaving of sensory inputs, memories and imagination. In this sense both imagination and perception are conceived by Neisser in terms of a kind of mental theatre in which our perceptions play themselves out.

Daniel Dennett, argues that this metaphor of the mind as a theatre in which cognitive images are somehow projected on a neural screen is a flawed throwback to the 17th Century Dualistic philosophy of René Descartes. Dualism claims that many mental phenomena are non-physical in nature and are thus clearly distinct from the material body and brain. Dennett rejects this notion in favour of a Physicalist position that treats all mental phenomena as purely physical in origin. For Dennett the theatre metaphor, or what he terms “The Cartesian Theatre”, presupposes a diminutive observer - a tiny homunculus - at the heart of consciousness who sits separate from the performance taking everything in. Dennett describes the nature of this misconception (sometimes called the Homunculus Fallacy) in the following video:

Interestingly, 1 minute and 24 seconds into the above video there is a cutaway shot to the audience. Sitting in the foreground of the auditorium, wearing a bright pink shirt, is an audience member taking everything in, not unlike a real-world version of the metaphor Dennett takes to task. The pink shirted individual is no less than Vilayanur Ramachandran, Director of the Center for Brain and Cognition at the University of California, San Diego. In the following video Ramachandran explains his colourful theory of how consciousness emerges as the result of the interrelations between a variety of brain functions. Ramachandran also introduces the concept of “meta-representation" in order to make a case for how he believes his theory might sidestep the homunculus fallacy.

"I'm saying that at some stage in evolution, instead of just sensory representations, you started creating what are called meta-representations: a representation of the representation, unlike the fruit-fly, which allows you to manipulate symbols internally in your head.”
Quite how Ramachandran thinks meta-representations avoid the homunculus fallacy is difficult to determine. Placing mental representations one inside the other simply adds yet more homunculi to what is already an endless list.

As previously mentioned, many philosophers and cognitive scientists make reference to meta-representations in their research. However, there is significant disagreement across different fields over the exact meaning of meta-representation (as discussed by Sam Scott here). Sometimes the term is used to describe a pictorial representation of a representation - as Daniel Dennett uses it, sometimes it is used to describe one's mental representations of one's other mental representations - as Ramachandran uses it above, sometimes it is used to describe a mental representation of an object as something that it is not (i.e. the child’s imaginary substitution of a banana for a telephone) and sometimes it is used to describe mental representations of other people’s mental representations: (i.e. Mary’s mental representation of Peter’s mental state). Regardless of the representational form, the underlying assumption of all meta-representational mind theory (i.e. all except perhaps Dennett) is that thought involves representations of one kind or another. As mentioned in parts III and IV, there are considerable grounds to doubt the common scientific, but as yet unsubstantiated, assumption that mental processes are representational in nature, let alone meta-representational.

Any theory that posits representation, of any kind, as a mental process must be entirely certain that it is founded upon an unshakeable understanding of the nature of representation. Moreover, it will need to explain how these processes of mental representation might have evolved from more rudimentary ancestral origins. Without fulfilling these two fundamental criteria, any proposed theory of imagination is likely to provide little in the way of insight.

But how could the mind function if not through the use of representations? This will be the subject of my next post.


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