Binding Problem - The Combination Problem

The Combination Problem

The binding problem, as it applies to the "unity of consciousness" is related to the problem of the homunculus—a putative inner "little man" who is the true subject within the brain. The question is how coloured squares and circles can be "experienced together" as a single scene. The implication is that something is experiencing all these data. It has become popular to deny any need to give a physical account of what it is that has the experience, often with the suggestion that it is the "person as a whole" or the "system". However, to ascribe input to such vague physical domains is not without problems. Such suggestions appear to arise from the common misconception that there cannot be a limited internal physical domain that has access to, for instance, data from blue sensitive and square sensitive cells. This domain is often equated with a "paradoxical" homunculus, but it is often not appreciated that a homunculus is only paradoxical under limited conditions. Sutherland denotes the fear of the homunculus as "homuphobia": "But if you look inside the brain you can't find any little green men and this has given rise to a fear of homunculi, agents and Cartesian theatres. All this has resulted in some desperate and flawed attempts to build a bottom-up theory."

The homunculus concept is often equated with someone "watching a wonderfully integrated internal TV screen" and, as René Descartes noted, nothing is more certain than that there is an internal observer ("Cogito ergo sum"), so the only alternative option to the homunculus is infinite regress (who is watching the screen inside the homunculus?). Some materialists refuse to accept the reality of subjective consciousness and so are led to conclude that infinite regress and homunculi are equally repugnant or absurd and so adopt the third alternative: eliminativism. Daniel Dennett maintains that "homunculi are only bogey men if they repeat entirely the talents they are rung in to explain". Limited domains within brains supporting percepts based on signals that have undergone several transductive steps almost certainly have to be postulated because much of brain activity appears to be outside consciousness. How signals are finally transduced into percepts in these domains remains a major mystery but there need be no further regress (again the regress/homunculus/eliminativism alternatives). What is much less clear is whether there is one such domain per brain or many, as in Dennett's "Multiple Draft" hypothesis.

The synchronisation of oscillating cellular potentials has also been invoked as a solution to the combination problem. Thus it was never very clear whether Francis Crick was trying to solve the segregation or the combination problem in his book The Astonishing Hypothesis However, one criticism of the synchronisation idea is that experiential combination of information in separate neurons is incompatible with any standard biophysical explanation of the brain, whether or not there is any synchrony. One possible explanation for binding is that the information is integrated in each of many individual downstream neurons. This requires that percepts exist in multiple complete copies. This difficulty has led many to suggest unconventional physical explanations for percepts, often invoking quantum theory (e.g. the approach of Freeman and Vitiello). Also, multiply experiencing neurons seems to make no sense if their experience is not pooled in a "global workspace" (see Bernard Baars or Cartesian theatre). And indeed they may be another example of a "desperate and flawed attempt" to build a bottom up theory.