Throughout the text, fundamental questions concerning the nature of visual perception are addressed.

While there is virtually a consensus among contemporary philosophers of perception that some form of direct realism is true, there is less than complete agreement about whether normal, direct perceptions involve mental inferences in any sense. In taking another look at this recurrent question, my aim is twofold: first, to examine some of the arguments and evidences that have been offered in favor of inferences and to see if they can be accommodated within the direct realist framework, and second, to (...) attempt to clarify and defend the insight of direct realism that normal perceptions are noninferential. (shrink)

Consider for a moment the spatial and chromatic dimensions of your visual expe- rience. Suppose that as you gaze about the room you see a table, some books, and papers. Ignore for now the fact that you immediately recognize these objects to be a table with books and papers on it. Concentrate on how the table looks to you: its top spreads out in front of you, stopping at edges beyond which lies un?lled space, leading to more or less distant (...) chairs, shelves, or expanses of ?oor. The books and paper on the table top create shaped visual boundaries between areas of different color, within which there may be further variation of color or visual texture. Propelled by a slight breeze, a sheet of paper slides across the table, and you experience its smooth motion before it ?oats out of sight. (shrink)

Interdisciplinary explorations of the implications of recent developments in vision theory for our understanding of the nature of pictorial representation and ...

Adults and infants display a robust ability to perceive the unity of a center-occluded object when the visible ends of the object undergo common motion (e.g. Kellman, P.J., Spelke, E.S., 1983. Perception of partly occluded objects in infancy. Cognitive Psychology 15, 483±524). Ecologically oriented accounts of this ability focus on the primacy of motion in the perception of segregated objects, but Gestalt theory suggests a broader possibility: observers may perceive object unity by detecting patterns of synchronous change, of which common (...) motion is a special case. We investigated this possibility with observations of adults and 4-month-old infants. Participants viewed a center-occluded object whose visible surfaces were either misaligned or aligned, stationary or moving, and unchanging or synchronously changing in color or bright- ness in various temporal patterns (e.g. ¯ashing). Both alignment and common motion con- tributed to adults' perception of object unity, but synchronous color changes did not. For infants, motion was an important determinant of object unity, but other synchronous changes and edge alignment were not. When a stationary object with aligned edges underwent syn- chronous changes in color or brightness, infants showed high levels of attention to the object, but their perception of its unity appeared to be indeterminate. An inherent preference for fast over slow ¯ash rates, and a novelty preference elicited by a change in rate, both indicated that infants detected the synchronous changes, although they failed to use them as information for object unity. These ®ndings favor ecologically oriented accounts of object perception in which surface motion plays a privileged role. Ó 1999 Elsevier Science B.V. All rights reserved. (shrink)

A preference method probed infants` perception of object motion on an inclined plane. Infants viewed videotaped events in which a ball rolled downward (or upward) while speeding up (or slowing down). Then infants were tested with events in which the ball moved in the opposite direction with appropriate or inappropriate acceleration. Infants aged 7 months, but not 5 months, looked longer at the test event with inappropriate acceleration, suggesting emerging sensitivity to gravity. A further study tested whether infants appreciate that (...) a stationary object released on an incline moves downward rather than upward; findings again were positive at 7 months and negative at 5 months. A final study provided evidence, nevertheless, that 5-monthold infants discriminate downward from upward motion and relate downward motion in videotaped events to downward motion in live events. Sensitivity to certain effects of gravity appears to develop in infancy. (shrink)

How are we able to perceive the world veridically? If we ask this question as a part of the scientific investigation of perception, then we are not asking for a transcendental guarantee that our perceptions are by and large veridical; we presuppose that they are. Unless we assumed that we perceived the world for the most part veridically, we would not be in a position to investigate our perceptual abilities empirically. We are interested, then, not in how it is possible (...) in general for us to perceive the world veridically, but instead in what the relation is between our environment and its properties, of which we have knowledge, on the one hand, and our perceptual mechanisms, on the other, that results in very many, even most of our perceptions being veridical in everyday life. (shrink)

It is a characteristic feature of our mental make-up that the same perceptual input situation can simultaneously elicit conflicting mental perspectives. This ability pervades our perceptual and cognitive domains. Striking examples are the dual character of pictures in picture perception, pretend play, or the ability to employ metaphors and allegories. I argue that traditional approaches, beyond being inadequate on principle grounds, are theoretically ill equipped to deal with these achievements. I then outline a theoretical perspective that has emerged from a (...) theoretical convergence of perceptual psychology, ethology, linguistics, and developmental research. On the basis of this framework, I argue that corresponding achievements are brought forth by a specific type of functional architecture whose core features are as follows: (1) a perceptual system that is biologically furnished with a rich system of conceptual forms, (2) a triggering relation between the sensory input and conceptual forms by which the same sensory input can be exploited by different types or systems of conceptual forms, and (3) computational principles for handling semantically underspecified conceptual forms. Characteristic features of the proposed theoretical framework are pointed out using the Heider–Simmel phenomenon as an example. (shrink)

'Epistemological constructivism' holds that vision is mediated by background preconceptions and is theory-laden. Hence, two persons with differing theoretical commitments see the world differently and they could agree on what they see only if they both espoused the same conceptual framework. This, in its turn, undermines the possibility of theory testing and choice on a common theory-neutral empirical basis. In this paper, I claim that the cognitive sciences suggest that a part of vision may be only indirectly penetrated by cognition (...) in a way that does not threaten retrieval of information from a visual scene in a bottom-up way. That blocks the constructivist epistemological thesis. However, since spatial attention, which can be cognitively driven, seems to permeate all stages of visual processes, one is led to conclude that there is no part of vision immune to direct cognitive interference. Against this, I elaborate on the role of spatial attention and argue that it does influence vision in a top-down manner, but it does so only in an indirect way. I then argue that the existence of visual processes that are only indirectly penetrated by cognition undermines the epistemological conclusions of constructivism. (shrink)

v. 1. Classical roots and medieval discussions -- v. 2. Renaissance controversis, later scholasticism, and the elimination of the intelligible species in modern philosophy.

The book I review, _Sleights of Mind_, aims to illuminate properties of perceptual systems by discussing human susceptibility to magical illusions. I describe how the authors use psychological principles to explain two tricks, spoon bending and the Miser's Dream. I also argue that the book is congenial to the following view of illusions: susceptibility to illusion is the result of evolutionary trade-offs; perceptual systems must make assumptions in order to function at all, but susceptibility to illusion is the byproduct of (...) such assumptions. (shrink)

Computational theories of vision typically rely on the analysis of two aspects of human visual function: (1) object and shape recognition (2) co-calibration of sensory measurements. Both these approaches are usually based on an inverse-optics model, where visual perception is viewed as a process of inference from a 2D retinal projection to a 3D percept within a Euclidean space schema. This paradigm has had great success in certain areas of vision science, but has been relatively less successful in understanding perceptual (...) representation, namely, the nature of the perceptual encoding. One of the drawbacks of inverse-optics approaches has been the difficulty in defining the constraints needed to make the inference computationally tractable (e.g. regularity assumptions, Bayesian priors, etc.). These constraints, thought to be learned assumptions about the nature of the physical and optical structures of the external world, have to be incorporated into any workable computational model in the inverse-optics paradigm. But inference models that employ an inverse optics plus structural assumptions approach inevitably result in a na. (shrink)