There is a long‐standing project in psychology the goal of which is to explain our ability to perceive speech. The project is motivated by evidence that seems to indicate that the cognitive processing to which speech sounds are subjected is somehow different from the normal processing employed in hearing. The Motor Theory of speech perception was proposed in the 1960s as an attempt to explain this specialness. The first part of this essay is concerned with the Motor (...) Theory's explanandum. It shows that it is rather hard to give a precise account of what the Motor Theory is a theory of. The second part of the essay identifies problems with the theory's explanans: There are difficulties in finding a plausible account of what the content of the Motor Theory is supposed to be. (shrink)

Action is a means of acquiring perceptual information about the environment. Turning around, for example, alters your spatial relations to surrounding objects and, hence, which of their properties you visually perceive. Moving your hand over an object’s surface enables you to feel its shape, temperature, and texture. Sniffing and walking around a room enables you to track down the source of an unpleasant smell. Active or passive movements of the body can also generate useful sources of perceptual information (Gibson 1966, (...) 1979). The pattern of optic flow in the retinal image produced by forward locomotion, for example, contains information about the direction in which you are heading, while motion parallax is a “cue” used by the visual system to estimate the relative distances of objects in your field of view. In these uncontroversial ways and others, perception is instrumentally dependent on action. According to an explanatory framework that Susan Hurley (1998) dubs the “Input-Output Picture”, the dependence of perception on action is purely instrumental: "Movement can alter sensory inputs and so result in different perceptions… changes in output are merely a means to changes in input, on which perception depends directly" (1998: 342). -/- The action-based theories of perception, reviewed in this entry, challenge the Input-Output Picture. They maintain that perception can also depend in a noninstrumental or constitutive way on action (or, more generally, on capacities for object-directed motor control). This position has taken many different forms in the history of philosophy and psychology. Most action-based theories of perception in the last 300 years, however, have looked to action in order to explain how vision, in particular, acquires either all or some of its spatial representational content. Accordingly, these are the theories on which we shall focus here. -/- We begin in Section 1 by discussing George Berkeley’s Towards a New Theory of Vision (1709), the historical locus classicus of action-based theories of perception, and one of the most influential texts on vision ever written. Berkeley argues that the basic or “proper” deliverance of vision is not an arrangement of voluminous objects in three-dimensional space, but rather a two-dimensional manifold of light and color. We then turn to a discussion of Lotze, Helmholtz, and the local sign doctrine. The “local signs” were felt cues for the mind to know what sort of spatial content to imbue visual experience with. For Lotze, these cues were “inflowing” kinaesthetic feelings that result from actually moving the eyes, while, for Helmholtz, they were “outflowing” motor commands sent to move the eyes. -/- In Section 2, we discuss sensorimotor contingency theories, which became prominent in the 20thcentury. These views maintain that an ability to predict the sensory consequences of self-initiated actions is necessary for perception. Among the motivations for this family of theories is the problem of visual direction constancy—why do objects appear to be stationary even though the locations on the retina to which they reflect light change with every eye movement?—as well as experiments on adaptation to optical rearrangement devices (ORDs) and sensory substitution. -/- Section 3 examines two other important 20th century theories. According to what we shall call the motor component theory, efference copies generated in the oculomotor system and/or proprioceptive feedback from eye-movements are used together with incoming sensory inputs to determine the spatial attributes of perceived objects. Efferent readiness theories, by contrast, look to the particular ways in which perceptual states prepare the observer to move and act in relation to the environment. The modest readiness theory, as we shall call it, claims that the way an object’s spatial attributes are represented in visual experience can be modulated by one or another form of covert action planning. The bold readiness theory argues for the stronger claim that perception just is covert readiness for action. -/- In Section 4, we move to the disposition theory, most influentially articulated by Gareth Evans (1982, 1985), but more recently defended by Rick Grush (2000, 2007). Evans’ theory is, at its core, very similar to the bold efferent readiness theory. There are some notable differences, though. Evans’ account is more finely articulated in some philosophical respects. It also does not posit a reduction of perception to behavioral dispositions, but rather posits that certain complicated relations between perceptual input and behavioral provide spatial content. Grush proposes a very specific theory that is like Evans’ in that it does not posit a reduction, but unlike Evans’ view, does not put behavioral dispositions and sensory input on an undifferentiated footing. (shrink)

The emulation theory of representation is developed and explored as a framework that can revealingly synthesize a wide variety of representational functions of the brain. The framework is based on constructs from control theory (forward models) and signal processing (Kalman filters). The idea is that in addition to simply engaging with the body and environment, the brain constructs neural circuits that act as models of the body and environment. During overt sensorimotor engagement, these models are driven by efference copies in (...) parallel with the body and environment, in order to provide expectations of the sensory feedback, and to enhance and process sensory information. These models can also be run off-line in order to produce imagery, estimate outcomes of different actions, and evaluate and develop motor plans. The framework is initially developed within the context of motor control, where it has been shown that inner models running in parallel with the body can reduce the effects of feedback delay problems. The same mechanisms can account for motor imagery as the off-line driving of the emulator via efference copies. The framework is extended to account for visual imagery as the off-line driving of an emulator of the motor-visual loop. I also show how such systems can provide for amodal spatial imagery. Perception, including visual perception, results from such models being used to form expectations of, and to interpret, sensory input. I close by briefly outlining other cognitive functions that might also be synthesized within this framework, including reasoning, theory of mind phenomena, and language. Key Words: efference copies; emulation theory of representation; forward models; Kalman filters; motor control; motor imagery; perception; visual imagery. (shrink)

The claim that perception and action are commonly coded because they are indistinguishable at the distal level is crucial for theories of cognition. However, the consequences of this claim run deep, and the Theory of Event Coding (TEC) is not up to the challenge it poses. We illustrate why through a brief review of the evidence that led to the motor theory of speech perception.

Several recent accounts claim that imagination is a matter of simulating perceptual acts. Although this point of view receives support from both phenomenological and empirical research, I claim that Jean-Paul Sartre's worry formulated in L'imagination (1936) still holds. For a number of reasons, Sartre heavily criticizes theories in which the sensory material of imaginative acts consists in reviving sensory impressions. Based on empirical and philosophical insights, this article explains how simulation theories of imagination can overcome Sartre's critique by (...) paying attention to the motor dimension of imagination. Intending to clarify the status of the sensory in imagination, a motor theory of imagination is presented in which the sensory component of imagination is interpreted in terms of anticipated sensory consequences of preparation for motor action. (shrink)

The two contrasting theoretical approaches to visual perception, the constructivist and the ecological, are briefly presented and illustrated through their analyses of space and size perception. Earlier calls for their reconciliation and unification are reviewed. Neurophysiological, neuropsychological, and psychophysical evidence for the existence of two quite distinct visual systems, the ventral and the dorsal, is presented. These two perceptual systems differ in their functions; the ventral system's central function is that of identification, while the dorsal system is mainly (...) engaged in the visual control of motor behavior. The strong parallels between the ecological approach and the functioning of the dorsal system, and between the constructivist approach and the functioning of the ventral system are noted. It is also shown that the experimental paradigms used by the proponents of these two approaches match the functions of the respective visual systems. A dual-process approach to visual perception emerges from this analysis, with the ecological-dorsal process transpiring mainly without conscious awareness, while the constructivist-ventral process is normally conscious. Some implications of this dual-process approach to visual-perceptual phenomena are presented, with emphasis on space perception. Key Words: constructivist; dual-process approach; ecological; size perception; space perception; two visual systems; visual perception theories. (shrink)

A review of the scanty Gestaltist literature on motor behaviour indicates that a genuine Gestalt theoretic approach to motor behaviour can be characterized by three research questions: (1) What are the natural units of motor behaviour? (2) What characterizes the self-organization in motor behaviour? (3) What are the conditions for invariance in motor behaviour? Tentative answers to these questions can be found by analysing the parallels between Gestalt theory and Bernstein's theory of motor actions (...) and by showing that Gestalt theory can be regarded as a specific approach to non-linear dynamics as exemplified by synergetics (Haken, 1991). The congruence between the Gestalt theoretic approach and synergetics becomes apparent in the analysis of how a complex motor task is learned [1]. (shrink)

Action perception and recognition are core abilities fundamental for human social interaction. A parieto-frontal network (the mirror neuron system) matches visually presented biological motion information onto observers' motor representations. This process of matching the actions of others onto our own sensorimotor repertoire is thought to be important for action recognition, providing a non-mediated “motor perception” based on a bidirectional flow of information along the mirror parieto-frontal circuits. State-of-the-art machine learning strategies for hand action identification have shown (...) better performances when sensorimotor data, as opposed to visual information only, are available during learning. As speech is a particular type of action (with acoustic targets), it is expected to activate a mirror neuron mechanism. Indeed, in speech perception, motor centers have been shown to be causally involved in the discrimination of speech sounds. In this paper, we review recent neurophysiological and machine learning-based studies showing (a) the specific contribution of the motor system to speech perception and (b) that automatic phone recognition is significantly improved when motor data are used during training of classifiers (as opposed to learning from purely auditory data). (shrink)

According to sensorimotor theory perceiving is a bodily skill involving exercise of an implicit know-how of the systematic ways that sensations change as a result of potential movements, that is, of sensorimotor contingencies. The theory has been most successfully applied to vision and touch, while perceptual modalities that rely less on overt exploration of the environment have not received as much attention. In addition, most research has focused on philosophically grounding the theory and on psychologically elucidating sensorimotor laws, but the (...) theory’s ramifications for neuroscience still remain underexamined. Here we sketch the beginnings of a research program that could address these two outstanding challenges in terms of auditory perception. We review the neuroscience literature on passive listening, which is defined as listening without overt bodily movement, and conclude that sensorimotor theory provides a unique perspective on the consistent finding of motor system activation. In contrast to competing theories, this activation is predicted to be involved not only in the perception of speech- and action-related sounds, but in auditory perception in general. More specifically, we propose that the auditory processing associated with supplementary motor areas forms part of the neural basis of the exercise of sensorimotor know-how: these areas’ recognized role in facilitating spontaneous motor responses to sound and supporting flexible engagement of sensorimotor processes to guide auditory experience and enable auditory imagery, can be understood in terms of two key characteristics of sensorimotor interaction, its “alerting capacity” and “corporality”, respectively. We also highlight that there is more to the inside of the body than the brain: there is an opportunity to develop sensorimotor theory into new directions in terms of the still poorly understood active processes of the peripheral auditory system. (shrink)

Control theory is a popular theoretical framework for explaining cognitive domains such as motor control and “mindreading.” Such accounts frequently characterize their “internal models” as “simulating” things outside the brain. But in what sense are these “simulations”? Do they involve the kind of “replication” simulation found in the simulation theory of mindreading? I will argue that some but not all control -theoretic appeals to “simulation” involve R-simulation. To do so, I examine in detail a recent computational model of (...) class='Hi'>motor control and action perception based in control theory. I argue that the architecture does not use R-simulation during motor control, but does during action perception. A novel result of this analysis is that the forward model—the control - theoretic mechanism most often described as performing simulation—is not well characterized in terms of R- simulation. I conclude with some lessons for research on the mechanisms of mindreading. (shrink)

This is an advanced introduction to and original interpretation of Merleau-Ponty's greatest work, Phenomenology of Perception. Timothy Mooney provides a clear and compelling exposition of the theory of our projective being in the world, and demonstrates as never before the centrality of the body schema in the theory. Thanks to the schema's motor intentionality our bodies inhabit and appropriate space: our postures and perceptual fields are organised schematically when we move to realise our projects. Thus our lived bodies (...) are ineliminably expressive in being both animated and outcome oriented through-and-through. Mooney also analyses the place of the work in the modern philosophical world, showing what Merleau-Ponty takes up from the Kantian and Phenomenological traditions and what he contributes to each. Casting a fresh light on his magnum opus, this book is essential reading for all those interested in the philosophy and phenomenology of the body. (shrink)

A comparison of disjunctive theories of action and perception. The development of a theory of action that warrants the name, a disjunctive theory. On this theory, there is an exclusive disjunction: either an action or an event (in one sense). It follows that in that sense basic actions do not have events intrinsic to them.

The Theory of Event Coding (TEC) provides a preliminary account of the interaction between perception and action, which is consistent with several recent findings in the area of motor control. Significant issues require integration and elaboration, however; particularly, distractor interference, automatic motor corrections, internal models of action, and neuroanatomical bases for the link between perception and action.

This paper tackles the problem of the nature of the space of perception. Based both on philosophical arguments and on results obtained from original experimental situations, it attempts to show how space is constituted concretely, before any distinction between the “inner” and the “outer” can be made. It thus sheds light on the presuppositions of the well-known debate between internalism and externalism in the philosophy of mind; it argues in favor of the latter position, but with arguments that are (...) foundationally antecedent to this debate. We call the position we defend enactive externalism. It is based on experimental settings which, in virtue of their minimalism, make it possible both to defend a sensori-motor/enactive theory of perception; and, especially, to inquire into the origin of the space of perception, showing how it is concretely enacted before the controversy between internalism and externalism can even take place. (shrink)

Recent advances in the cognitive neuroscience of action have considerably enlarged our understanding of human motor cognition. In particular, the activity of the mirror system, first discovered in the brain of non-human primates, provides an observer with the understanding of a perceived action by means of the motor simulation of the agent's observed movements. This discovery has raised the prospects of a motor theory of social cognition. Since human social cognition includes the ability to mindread, many (...) class='Hi'>motor theorists of social cognition try to bridge the gap between motor cognition and mindreading by endorsing a simulation account of mindreading. Here, we express our skepticism about the motor theory of social cognition. (shrink)

In recent years, the rich tradition of various philosophical theories of perception has been increasingly studied by scholars of the history of philosophy of ...

Various defenses of amodal symbol systems are addressed, including amodal symbols in sensory-motor areas, the causal theory of concepts, supramodal concepts, latent semantic analysis, and abstracted amodal symbols. Various aspects of perceptual symbol systems are clarified and developed, including perception, features, simulators, category structure, frames, analogy, introspection, situated action, and development. Particular attention is given to abstract concepts, language, and computational mechanisms.

Presented here in a lucid, simple style is an extended defense of a behavioral and direct-realist theory of sense perception. Originally published in 1971. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These paperback editions preserve the original texts of these important books while presenting them in durable paperback editions. The goal of the Princeton Legacy Library is to vastly increase access to the (...) rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905. (shrink)

The notion of repression as active forgetfulness already found in Nietzsche and systematised by Freud and his successors is employed in a distinctive manner by Merleau-Ponty in Phenomenology of Perception. By showing how we appropriate our environment towards outcomes and respond to other people, he contends, we can unearth hidden modes of operative intentionality. Two such modes are the motor intentional projection of action and the anonymous intercorporeality that includes touching and being touched. Each of these is an (...) aspect of a past that was never a present. Merleau-Ponty does have something to say about pasts that were once present and that linger on in human life. Yet he shows little interest in the unconsciousness of psychoanalysis for its own sake. Psychoanalytic accounts of repression are assimilated into his theory of the body itself, serving merely as means for illustrating the latter. I suggest that this move follows on a conception of an integrated existent whose past acquisitions are remarkably enabling and untroubling. (shrink)

A philosphical exploration of perception explores Wittgenstein's work on visual meaning and his analysis of the concept of "seeing.".

Presented here in a lucid, simple style is an extended defense of a behavioral and direct-realist theory of sense perception. Originally published in 1971. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to (...) the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905. (shrink)

The title refers to theories that require a certain sort of relation between X and an experience of S in order that S perceive X. The relation might be causal, counterfactual, doxastic, or otherwise. It is argued against such theories that there are possible cases in which X stands in the required relation to an experience of S and S does not perceive X and cases in which X is perceived though it does not stand in the required (...) relation. (shrink)

Nichols offers the first comprehensive interpretation of the eighteenth-century Scottish philosopher Thomas Reid's theory of perception - by far the most important feature of his philosophical system. Nichols's consummate knowledge of Reid's texts, lively examples, and plainspoken style make this book especially readable. It will be the definitive analysis for a long time to come.

For over a century and certainly since single-unit recordings in the 1960s the theory of perception that has dominated thinking and research, with implications for the understanding of all other cognitive domains, entails a neocortical process of progressive assembly from V-1 to V-4 leading to object-construction and secondary spatial updating and recognition. In recent years, however, difficulties with the theory have emerged in neurophysiological research though a compelling alternative has not been forcefully argued. It is the purpose of this (...) paper to review the main features of the microgenetic account of perception, which inverts standard theory 180 degrees, and aligns the perceptual process with patterns of evolutionary growth. This theory developed on clinical study, and perhaps for this reason has not received sufficient attention, in mainstream cognitive and affective neuroscience, though it provides an account not only of perception but of stages in memory, imagery, the present moment, and the mind/brain state. (shrink)

The overall goal of this target article is to demonstrate a mechanism for an embodied cognition. The particular vehicle is a much-studied, but still widely debated phenomenon seen in 7–12 month-old-infants. In Piaget's classic “A-not-B error,” infants who have successfully uncovered a toy at location “A” continue to reach to that location even after they watch the toy hidden in a nearby location “B.” Here, we question the traditional explanations of the error as an indicator of infants' concepts of objects (...) or other static mental structures. Instead, we demonstrate that the A-not-B error and its previously puzzling contextual variations can be understood by the coupled dynamics of the ordinary processes of goal-directed actions: looking, planning, reaching, and remembering. We offer a formal dynamic theory and model based on cognitive embodiment that both simulates the known A-not-B effects and offers novel predictions that match new experimental results. The demonstration supports an embodied view by casting the mental events involved in perception, planning, deciding, and remembering in the same analogic dynamic language as that used to describe bodily movement, so that they may be continuously meshed. We maintain that this mesh is a pre-eminently cognitive act of “knowing” not only in infancy but also in everyday activities throughout the life span. Key Words: cognitive development; dynamical systems theory; embodied cognition; infant development; motor control; motor planning; perception and action. (shrink)

In this essay Elizabeth de Freitas follows Tim Ingold's groundbreaking anthropological work on lines and their cultural and material significance to argue that the line is the engine of theory, be it the drawn line of inscription or mathematical measure, the exclusionary line of delineation, or the undulating generative line of flight. De Freitas focuses on contemporary theories of perception that deploy the line — and mobilize the force of theory — so as to encode and reconfigure the (...) student's body. She draws on the work of Gilles Deleuze to develop a topological approach to the line, and argues that such an approach aligns with current philosophical approaches to social interaction that might be termed “topo-philosophy.”. (shrink)

A theory is proposed that views emotional feelings as pivotal for action control. Feelings of emotions are valued interoceptive signals from the body that become multimodally integrated with perceptual contents from registered and mentally simulated events. During the simulation of a perceptual change from one event to the next, a conative feeling signal is created that codes for the wanting of a specific perceptual change. A wanted perceptual change is weighted more strongly than alternatives, increasing its activation level on the (...) cognitive level and that of associated motor structures that produced this perceptual change in the past. As a consequence, a tendency for action is generated that is directed at the production of the wanted perception. (shrink)

Summary An attempt is made in this book to expound the Buddhist theory of perception as conceived by Dinnaga and Dharmkirti, especially as presented in Pramanavarttika of the latter. The study is divided into nine chapters. The first chapter deals with the Dinaga-Dharmakirti logico-epistemological sub-system within the overall system of Buddhist philosophy. The second chapter brings out the unique contribution of Pramanavarttika as a commentary to Pramanasamuccaya of Dinnaga. The third and fourth chapters are focused on the pre-Dinnaga and (...) non-Buddhist theories of perception. The fifth chapter deals with Dharmkirti’s well- reasoned addition of the term ‘non-illusive” to the definition of perception as given by Dinnaga. The sixth chapter is devoted to the main theme freedom from conceptual construction or kalpnapodham as the definiens of the term pratyaksha. The seventh chapter is about the four kinds of perception. The eighth chapter deals with the nature of the object of perception, the criteria of valid perception along with a discussion on illusion. The ninth chapter sums up the relevance of Pramanavarttika’ s contribution to Buddhist philosophy. (shrink)

This is a paper about The Causal Self-Referential Theory of Perception. According to The Causal Self-Referential Theory as developed by above all John Searle and David Woodruff Smith, perceptual content is satisfied by an object only if the object in question has caused the perceptual experience. I argue initially that Searle's account cannot explain the distinction between hallucination and illusion since it requires that the state of affairs that is presented in the perceptual experience must exist in order for (...) the perception to be veridical. Smith's account is interestingly different in that the descriptive content, i.e. the content that presents the perceptual object as having certain properties, does not determine the object of the experience. His account consequently does not require that the state of affairs that is presented in perception exists in order for the perception to have an object. Smith argues instead that perceptual reference is determined by a specific kind of demonstrative content. In this paper it is argued that Smith's account of demonstrative content is too indeterminate and in certain circumstances prescribes the wrong object. It is subsequently argued that the theory of demonstrative content can be modified so as to avoid these consequences. This modification involves deriving the conditions of satisfaction of seeing an object from the conditions of satisfaction of seeing the shape of the object, where the shape of the object is conceived of as a particularized property, what is also called a ‘trope’. (shrink)

It is generally agreed upon that Grice's causal theory of perception describes a necessary condition for perception. It does not describe sufficient conditions, however, since there are entities in causal chains that we do not perceive and not all causal chains yield perceptions. One strategy for overcoming these problems is that of strengthening the notion of causality. Another is that of specifying the criteria according to which perceptual experiences should match the way the world is. Finally, one can (...) also try to provide sufficient conditions by elaborating on the content of perceptual experiences. These different strategies are considered in this paper, with the conclusion that none of them is successful. However, a careful examination of their problems points towards the general solution that we outline at the end. (shrink)

Hintikka has criticized psychologists for "hasty epistemologizing," which he takes to be an unwarranted transfer of ideas from psychology (a discipline dealing with questions of fact) into epistemology (a discipline dealing with questions of method and theory). Hamlyn argues, following Hintikka, that Gibson's theory of perception is an example of such an inappropriate transfer, especially insofar as Hamlyn feels Gibson does not answer several important questions. However, Gibson's theory does answer the relevant questions, albeit in a new and radical (...) way, which suggests that the alleged distinction between psychology and epistemology is suspect. In fact, contrary to Hintikka and Hamlyn's claims, Gibson's theory of perception appears to be a valuable source of epistemological as well as psychological ideas. (shrink)

The article covers such issues as the relevance of the theory of perception as a multi-level information processing, the methodological role of the concept of representation and the relation of neurodynamic structures to subjective experience. The author critically reviews the philosophical presumptions underlying the various concepts of “local rationality,” the core of which is constituted by the belief that large ethnic cultures generate or are based on their own rationality and their own logic. Three statements are successively considered: thinking (...) is based on the inherent rules of rationality, logic is an extract of rationality, and types of rationality are geographically consistent with large ethnocultural communities. Empirical arguments are presented that demonstrate equivocality of the first two theses. In particular, firstly, it is shown that the genuine rationality of thinking lies not in following the rules that are immanent to it, but in the development of thinking and, more broadly, cognitive operations towards optimization of certain indicators of the cognitive or motor system that are important for survival and adaptation. In addition, this rationality is multivariate, and the choice between variants is often weakly determined or even random. Thus, the first statement turns out to be refuted. Secondly, by reference to the well-known experiments, it is shown that most people do not explicitly follow some declared logical rules in solving even logical or mathematical problems, and yet there is reason to consider their behavior rational. The third thesis, as shown with some limited empirical material, appears to be partially confirmed. Nevertheless, the demonstration of the doubtfulness of the first two theses makes the conclusion that different nations have different logics insufficiently substantiated. (shrink)

A survey of work on the philosophy of perception, mind, and mental representation by Berkeley and his early modern predecessors, notably Descartes, Hobbes, Malebranche, and Locke.

Anthony J. Lisska presents a new analysis of Thomas Aquinas's theory of perception. While much work has been undertaken on Aquinas's texts, little has been devoted principally to his theory of perception and less still on a discussion of inner sense. The thesis of intentionality serves as the philosophical backdrop of this analysis while incorporating insights from Brentano and from recent scholarship. The principal thrust is on the importance of inner sense, a much-overlooked area of Aquinas's philosophy of (...) mind, with special reference to the vis cogitativa. Approaching the texts of Aquinas from contemporary analytic philosophy, Lisska suggests a modest 'innate' or 'structured' interpretation for the role of this inner sense faculty. He argues that were it not for the vis cogitativa, Aquinas would be unable to account for an awareness of the principal ontological category in his metaphysics. (shrink)

Comparisons are drawn between two theories of visual perception and two modes of information processing. Characteristics delineating dorsal and ventral visual systems lack internal consistency, probably because they are not completely separable. Mechanism is inherent when distinguishing these systems, and becomes more apparent with different processing domains. What is lacking is a more explicit means of linking these theories.