Tacca
Commonalities between perception and cognition
Thus, feature binding turns out to be more than an associative
process that merely links inputs to outputs. In fact, visual bind-
ing by spatial attention displays a systematic competency: first, the
visual system implements a mereological structure of constituents,
rather than processing arbitrarily correlated inputs. Second, the
proposed model of visual feature binding displays a systematic
structure of constituents. As outlined above, structurally related
visual scenes share the same, but differently arranged, primitive
features.
Systematicity is a property displayed by both sentential-
cognitive representations and spatial representations. This con-
clusion is in contrast with previous works in philosophy (
Clark,
2004b
;
Fodor, 2008
), according to which only representations with
a language-like format combine constituents in a way such that
a small set of primitive representations can be recombined to
form different types of complex representations. In particular,
Clark (2004b, p. 571) suggests that sensory states “have something
like a subject–predicate structure, though they are not sentential
and do not manifest most of the hallmarks of compositional-
ity.” In a classical account, a systematic structure of constituents
is a distinctive feature of, and tightly related to, compositionality
(
Fodor, 1998
). The requirement of systematicity is explained in
terms of the syntactic structure of constituent recombination in
thought, whilst compositionality concerns the content of propo-
sitional representations. The main idea is that the content of
a thought depends on the content of its constituents and the
way they are syntactically combined. The reason Clark argues
that visual representations do not have traits that satisfy com-
positionality is because those representations, arising from the
binding of primitive features, provide the basis for the concep-
tual identification of particulars but do not themselves involve
conceptual identification; namely, visual primitive representations
do not contribute their content to the content of the final object
representation.
I argue, instead, that if a system has a structure of contentful
constituents, then this system displays at least one of the hallmarks
of compositionality: systematicity. It can also be shown that visual
representations satisfy a deflationary notion of compositional-
ity – a weaker form of compositionality than the one mentioned
here (
Tacca, 2010
). A deflationary account only requires that (i)
vision has a systematic structure, and that (ii) visual primitive
constituents have a specific content. But it remains neutral on
which types of semantic properties compose, as required by a clas-
sical account of compositionality (
Fodor and Lepore, 2001
). This
is a consequence of the spatial, rather than sentential, character
of visual representations. In fact, as Clark notices, visual repre-
sentations are indeed not sentential. This seems to be the case
for both primitive features that are bound at intermediate visual
stages and for more complex representations that occur at late
visual stages.
The spatial nature of visual representations also makes the
systematicity of visual representations different from the sys-
tematicity of cognitive representations. The explanation of the
systematicity of thought involves two parts (
Cummins et al.,
2001
): (i) it entails that having a thought requires having men-
tal representations that express that thought. This also applies
to visual representations, since to represent a visual object, the
primitive representations that code for its characteristics have to
be tokened; and (ii) it entails that mental representations have
a language-like combinatorial syntax (and semantic). This is not
the case for visual representations. Spatial recombinations under-
lying visual object representation lack the operational repertoire
of language-like recombinations. Visual feature binding requires
the integration (and spatial grouping) of local, primitive fea-
tures. To this extent, operations like conjunction and identity
are required. But it is not possible to characterize any of the
processes involved in binding in terms of other logical oper-
ations. No “visual negation” or “visual disjunction” take place.
There is no feature integration that is the negation of any of the
integrations that occur within the visual system, and, in con-
trast with feature conjunction, an explicit feature disjunction
does not exist in vision: either features are conjoint or they are
not combined at all. In sum, vision does not possess the rich
propositional structure that higher-cognitive processes seem to
have.
The fact that visual representations do not have a proposi-
tional nature highlights the difference in combinatorial processes
between the visual and perceptual systems but it does not rule out
the possibility that systems with different combinatorial struc-
tures can implement the same combinatorial requirement, even if
in different ways. This is the case for visual representations that,
even if they do not allow for propositional recombinations, dis-
play systematicity. Thus, the requirement of systematicity can be
considered as a general property that does not depend on the type
of operations performed on the primitive constituents.
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