Using a novel enumeration task, we examined the encoding of spatial information during subitizing. Observers were shown masked presentations of randomly-placed discs on a screen and were required to mark the perceived locations of these discs on a subsequent blank screen. This provided a measure of recall for object locations and an indirect measure of display numerosity. Observers were tested on three stimulus durations and eight numerosities. Enumeration performance was high for displays containing up to six discs—a higher subitizing range (...) than reported in previous studies. Error in the location data was measured as the distance between corresponding stimulus and response discs. Overall, location errors increased in magnitude with larger numerosities and shorter display durations. When errors were computed as disc distance from display centroid, results suggest a compressed representation by observers. Additionally, enumeration and localization accuracy increased with display regularity. (shrink)

Aspetti filosofico-matematici dei celebri paradossi di Zenone di Elea.

This book has three principle aims: to show that neither vision nor mental imagery involves the creation or inspection of picture-like mental representations; to defend the claim that our visual processes are, in significant part, cognitively impenetrable; and to develop a theory of “visual indexes”. In what follows, I assess Pylyshyn’s success in realising each of these aims in turn. I focus primarily on his arguments against “picture theories” of vision and mental imagery, to which approximately half the book is (...) devoted. I argue that Pylyshyn adopts an unnecessarily restricted interpretation of what it would be for mental representations to be picture-like, and that this leads him prematurely to reject the possibility of explaining the introspective evidence concerning the nature of mental imagery. (shrink)

In this paper I reconstruct and discuss Antonio Rubio (1546-1615)’s theory of the composition of the continuum, as set out in his Tractatus de compositione continui, a part of his influential commentary on Aristotle’s Physics, published in 1605 but rewritten in 1606. Here I attempt especially to show that Rubio’s is a significant case of Scholastic overlapping between Aristotle’s theory of infinitely divisible parts and indivisibilism or ‘Zenonism’, i.e. the theory that allows for indivisibles, extensionless points, lines, and surfaces, (...) which are supposed to take part in the composition of the continuum. Even if such a syncretic tendency was, in many different ways, already developing in the medieval period and then at the end of the sixteenth century, Rubio’s position is indeed peculiar. He maintains that indivisibles are real and actual, infinite in act, really distinct from each other, and that, although they indwell in substance, indivisibles do not contribute directly to the constitution of the continuum. In this reconstruction, I emphasize notably Rubio’s usage of mereological notions like those of part, whole, completeness and incompleteness. (shrink)

Zenon Pylyshyn argues that cognitively driven attentional effects do not amount to cognitive penetration of early vision because such effects occur either before or after early vision. Critics object that in fact such effects occur at all levels of perceptual processing. We argue that Pylyshyn’s claim is correct—but not for the reason he emphasizes. Even if his critics are correct that attentional effects are not external to early vision, these effects do not satisfy Pylyshyn’s requirements that the effects be direct (...) and exhibit semantic coherence. In addition, we distinguish our defense from those found in recent work by Raftopoulos and by Firestone and Scholl, argue that attention should not be assimilated to expectation, and discuss alternative characterizations of cognitive penetrability, advocating a kind of pluralism. (shrink)

In this short paper, I outline four philosophical arguments concerning the objects we perceive. These arguments build up to the conclusion that the objects of perceptual experience are material objects. I then show that the first three of these arguments parallel important psychological positions in vision science. Thus, (1) the notion of object used in Logical Atomism resembles the concept as it is defined in the Feature Integration Theory of Treisman and Gelade (1980). But (2) Frank Jackson's (1975) Many-Property Problem (...) leads to a substrate-quality structure for visual experience that corresponds to the structure of attended experience in Feature Integration Theory. A third philosophical argument (3) concerns the perception of movement. This argument culminates in the proposition that perceptual features are seen as belonging to material objects. There is a close resemblance between these objects and those of Zenon Pylyshyn's (1980) FINSTs. Finally, (4) I argue that material objects are the only substrates of multimodal perceptual experience. Perceptual psychology has yet to investigate this structure. (shrink)

Object files are mental representations that enable perceptual systems to keep track of objects as numerically the same. How is their reference fixed? A prominent approach, championed by Zenon Pylyshyn and John Campbell, makes room for a non-satisfactional use of properties to fix reference. This maneuver has enabled them to reconcile a singularist view of reference with the intuition that properties must play a role in reference fixing. This paper examines Campbell’s influential defense of this strategy. After criticizing it, a (...) new approach is sketched. The alternative view introduces representational contents to explain perceptual individuation. After arguing that those contents are not satisfactional, it is concluded that there is room for a third view of reference fixing that does not fit into the singularist/descriptivist dichotomy. (shrink)

In this paper I reconstruct and discuss Antonio Rubio (1546-1615)’s theory of the composition of the continuum, as set out in his Tractatus de compositione continui, a part of his influential commentary on Aristotle’s Physics, published in 1605 but rewritten in 1606. Here I attempt especially to show that Rubio’s is a significant case of Scholastic overlapping between Aristotle’s theory of infinitely divisible parts and indivisibilism or ‘Zenonism’, i.e. the theory that allows for indivisibles, extensionless points, lines, and surfaces, (...) which are supposed to take part in the composition of the continuum. Even if such a syncretic tendency was, in many different ways, already developing in the medieval period and then at the end of the sixteenth century, Rubio’s position is indeed peculiar. He maintains that indivisibles are real and actual, infinite in act, really distinct from each other, and that, although they indwell in substance, indivisibles do not contribute directly to the constitution of the continuum. In this reconstruction I emphasize notably Rubio’s usage of mereological notions like those of part, whole, completeness and incompleteness. (shrink)

Since the early eighties, computationalism in the study of the mind has been “under attack” by several critics of the so-called “classic” or “symbolic” approaches in AI and cognitive science. Computationalism was generically identified with such approaches. For example, it was identified with both Allen Newell and Herbert Simon’s Physical Symbol System Hypothesis and Jerry Fodor’s theory of Language of Thought, usually without taking into account the fact ,that such approaches are very different as to their methods and aims. Zenon (...) Pylyshyn, in his influential book Computation and Cognition, claimed that both Newell and Fodor deeply influenced his ideas on cognition as computation. This probably added to the confusion, as many people still consider Pylyshyn’s book as paradigmatic of the computational approach in the study of the mind. Since then, cognitive scientists, AI researchers and also philosophers of the mind have been asked to take sides on different “paradigms” that have from time to time been proposed as opponents of (classic or symbolic) computationalism. Examples of such oppositions are: -/- computationalism vs. connectionism, computationalism vs. dynamical systems, computationalism vs. situated and embodied cognition, computationalism vs. behavioural and evolutionary robotics. -/- Our preliminary claim in section 1 is that computationalism should not be identified with what we would call the “paradigm (based on the metaphor) of the computer” (in the following, PoC). PoC is the (rather vague) statement that the mind functions “as a digital computer”. Actually, PoC is a restrictive version of computationalism, and nobody ever seriously upheld it, except in some rough versions of the computational approach and in some popular discussions about it. Usually, PoC is used as a straw man in many arguments against computationalism. In section 1 we look in some detail at PoC’s claims and argue that computationalism cannot be identified with PoC. In section 2 we point out that certain anticomputationalist arguments are based on this misleading identification. In section 3 we suggest that the view of the levels of explanation proposed by David Marr could clarify certain points of the debate on computationalism. In section 4 we touch on a controversial issue, namely the possibility of developing a notion of analog computation, similar to the notion of digital computation. A short conclusion follows in section 5. (shrink)

Pylyshyn restricts cognitively penetrable vision to late vision, whereas he does not make any distinction between different kinds of penetrating cognition. I argue that this approach disconnects early vision content from late vision content and blurs the distinction between the latter and the content of thought. To overcome this problem I suggest that we should not distinguish between different kinds of visual content but instead introduce a restriction on the kind of cognition that can directly penetrate visual experience. In particular, (...) I suggest that visual experience, unlike thought, is directly penetrated only by practical non-propositional knowledge. I specify this weak cognitive penetrability in anti-representational terms. In particular, I suggest that the dependence of visual content on practical non-propositional knowledge should be conceived as a rational non-inferential relation, for it is in this way that we can account for the distinctive content of visual experience. (shrink)

Pylyshyn restricts cognitively penetrable vision to late vision, whereas he does not make any distinction between different kinds of penetrating cognition. I argue that this approach disconnects early vision content from late vision content and blurs the distinction between the latter and the content of thought. To overcome this problem I suggest that we should not distinguish between different kinds of visual content but instead introduce a restriction on the kind of cognition that can directly penetrate visual experience. In particular, (...) I suggest that visual experience, unlike thought, is directly penetrated only by practical non-propositional knowledge. I specify this weak cognitive penetrability in anti-representational terms. In particular, I suggest that the dependence of visual content on practical non-propositional knowledge should be conceived as a rational non-inferential relation, for it is in this way that we can account for the distinctive content of visual experience. (shrink)