Michela C. Tacca: Looking at Vision from Different Point of View - Systematicity and Compositionality of Visual Feature Binding

The visual system is a representational system with processes operating on structured nonconceptual mental representations. According to a common assumption in philosophy, the structure of the visual system fundamentally differs from the structure of higher-level representational systems, such as thought. Specifically, vision does not satisfy the Generality Constraint (i.e., a constraint on the combinatorial structure of mental representations), and, therefore, the visual system is not systematic. From the fact that it is commonly assumed that the structure of vision fundamentally differs from the structure of higher-cognitive processes, it does not follow that vision is not systematic. Particularly, I argue that visual representations have a structure of constituents, and as such are systematic. To this end, I consider results from psychophysical and neurophysiological studies of visual feature binding (i.e., how visual elementary features are bound into objects), and integrate these findings with my theoretical analysis of the structure of vision. It turns out that visual binding operations exploit objects’ location in space for recombining primitive visual constituents (i.e., primitive features such as color, motion, and shape), and that these spatial recombinations are systematic. Hence, vision has a systematic structure of constituents, even if it lacks the language-like structure typical of higher-level cognitive systems. Since the explanation of systematicity presupposes compositionality, I consider whether the binding operations underlying object perception have a compositional structure of constituents, namely, whether the content of an object representation depends on the content of its constituents. I argue that, because of the nonconceptual nature of visual representations, the compositionality of vision is better described as syntactic compositionality. I conclude that systematicity and compositionality do not depend on the particular structure of a system but, instead, are general properties of representational systems with combinatorial processes. More generally, as opposed to Evans’ Generality Constraint, the systematic structure of thought might be inherited by the systematic structure of the binding operations underlying object representation.