Suitability of actions in the world are tested within the duration of the present by the circular function of the sensory-motor loop which continuously corrects itself in relation to the environment. This ongoing process of correcting behaviour, effected by closing the sensory-motor loops, is the most fundamental test of reality. This is how behaviour is kept consistent with our interactions with the world in the present, in the ‘here and now’.
The construction of complex percepts arising from all sensory inputs, the mental representation of ‘objects’, is described as the ‘binding process’. For example, visual inputs from the primary occipital cortex project to different parts of the occipital association cortex which deal separately with motion, colours and face recognition before becoming integrated with other touch and auditory inputs to generate the feeling of perceiving a unique ‘object’1. The nature of this process has been well illustrated by understanding how optical illusions are generated.
A question often raised is whether we actually perceive reality or are our minds constantly ‘hallucinating’, ie creating imaginary inner experiences which in normal people are constrained by closing the experiential loops, keeping us consistent with the external world within the here and now. This idea was first proposed by Rodolfo Llinás, an Argentinian neuroscientist who considered that our experience of reality is a constrained dream2. According to him, the brain constructs a ‘reality’ which is in principle imaginary or illusionary. The illusions that do not correspond to the outside world when tested via various parallel mechanism remain illusions; those for which there is are counterparts in the external world but not in the here and now are hallucinations; only those which match and meet the reality test of the experiential loop correspond to biologically relevant, credible elements in the external world.
We have seen that there are two kinds of experiences of the external world: direct ones that can only be experienced within the window of the present; and indirect ones that need to be brought within that window via memory or imagination. Both are unavoidable consequences of a nervous system that distinguishes between a present for action and a past or future in which is only possible to remember or imagine actions.
Unifying these two different aspects of reality within a biological view may resolve the problem posed since early thinkers, of which one of the two is the ‘true’ reality. On one hand, it was suggested that the only reality is the one experienced in the present and within which we are indisputably embedded (for example, the Epicurean and Stoic philosophers). On the other hand, many thinkers since the origin of humankind thought that the true reality lies beyond the senses and is hidden behind a world of appearances (for example, Plato, Pythagoras and most of modern physical sciences). We can see now that both ‘realities’ are the result of different ways of building experiences and thus how we come to know something of a single world. One ‘reality’ lies within a thin spatio-temporal slice of the here and now, the other ‘reality’ encompasses everything else, that is necessarily brought within the slice of the present experience. In both cases, it is necessary to provide a test to convince one that behind a certain experience there is a phenomenon in the outside world that justifies it.
The validity of this test boils down to the problem of how we can establish if an experience corresponds to something out there in the external world: this is the closing of the experiential loop mentioned above. If the subjective experience of something outside us coincides with all sensory inputs that we receive and is consistent with our behaviour, then we can say that the sensory motor (mechanical-mechanical) loop is closed and has put us in appropriate contact with the external reality. For example, if I see, touch and taste an espresso coffee, it is most likely that there is indeed a cup of coffee out there.
The definition of reality under this perspective requires not only the construction of an experience in the brain, but also of testing if there is a good correspondence of the experience with the external world. This continuous closing of the sensory-motor loops keeps the virtual states of the mind in check to generate ‘real’ experiences of the world instead of merely imaginary ones. This verification is thus a biologically-based process that enables a method to establish whether or not an organism constructs a virtual (mental) world compatible with the external (physical) world.