Disturbance of Ecological Self and Impairment of Affordance Perception.

Affordance, a radical concept James Gibson introduced in the 1970s, remains controversial today. Defined as environmental properties taken with reference to an animal's anatomy and action capabilities, affordances are opportunities for action the environment offers. By perceiving affordances, organisms hold meaningful relationships with their surroundings.

Impaired Affordance Perception as the Basis of Tool Use Deficiency in Alzheimer's Disease.

The present study investigated whether defective affordance perception capacity underpins tool use deficits in patients with Alzheimer's disease (AD). An affordance, a concept James Gibson introduced, scales environmental objects to an animal's action capabilities, thus offering opportunities for action. Each man-made artifact carries both a primary affordance (its designed function) and secondary affordances.

Stereoscopic Depth Perception and Visuospatial Dysfunction in Alzheimer's Disease.

With visuospatial dysfunction emerging as a potential marker that can detect Alzheimer's disease (AD) even in its earliest stages and with disturbance in stereopsis suspected to be the prime contributor to visuospatial deficits in AD, we assessed stereoscopic abilities of patients with AD and mild cognitive impairment (MCI). Whereas previous research assessing patients' stereoacuity has yielded mixed results, we assessed patients' capacity to process coarse disparities that can convey adequate depth information about objects in the environment. We produced two virtual cubes at two different distances from the observer by manipulating disparity type (absolute vs.

Independence of Size and Distance in Binocular Vision.

For too long, the size distance invariance hypothesis (SDIH) has been the prevalent explanation for size perception. Despite inconclusive evidence, the SDIH has endured, primarily due to lack of suitable information sources for size perception. Because it was derived using the geometry of monocular viewing, another issue is whether the SDIH can encompass binocular vision.

A Binocular Information Source for Size Perception.

For too long, size perception research has been guided by the size distance invariance hypothesis. Although research to validate this hypothesis has been largely inconclusive, the hypothesis has endured, perhaps in part because alternative information sources for size perception were lacking. Here, I propose a binocular information source for size perception.

Schizophrenia: An Impairment in the Capacity to Perceive Affordances.

Phenomenological psychopathologists conceptualize schizophrenia as a self-disorder involving profound distortions of selfhood. For James Gibson, "to perceive the world is to coperceive oneself." If the sense of self is disturbed in individuals with schizophrenia, this could also lead to disturbances in these individuals' ability to perceive affordances, environmental properties taken with reference to the perceiver's action capabilities (e.

How Facial Expressions of Emotion Affect Distance Perception.

Facial expressions of emotion are thought to convey expressers' behavioral intentions, thus priming observers' approach and avoidance tendencies appropriately. The present study examined whether detecting expressions of behavioral intent influences perceivers' estimation of the expresser's distance from them. Eighteen undergraduates (nine male and nine female) participated in the study.

Perceiving Collision Impacts in Alzheimer's Disease: The Effect of Retinal Eccentricity on Optic Flow Deficits.

The present study explored whether the optic flow deficit in Alzheimer's disease (AD) reported in the literature transfers to different types of optic flow, in particular, one that specifies collision impacts with upcoming surfaces, with a special focus on the effect of retinal eccentricity. Displays simulated observer movement over a ground plane toward obstacles lying in the observer's path. Optical expansion was modulated by varying [Formula: see text].

PERCEIVING TIME-TO-CONTACT UNDER LOCALLY IMPOVERISHED OPTICAL FLOW.

As an object approaches an observer, the visual angle subtended by any two texture elements on the object surface expands, as does the solid angle corresponding to the object's contour. The inverse of the relative rate of each of these types of expansion specifies the time-to-contact (TTC) between the object and the observer. The former is referred to as local tau1 (LT1), and the latter as local tau2 (LT2).

Loss of sensitivity to dynamic occlusion in patients with Alzheimer's disease.

The current study examined whether diminished sensitivity to dynamic occlusion in Alzheimer's disease (AD) contributes to reduced capacity to recover 3D shape from motion. Young controls, age-matched elderly controls, and AD patients participated in the study. Participants watched computer simulations of an object, depicted as either transparent or opaque, rotating about the vertical axis against a background rendered in random dot texture.

Learning to perceive structure from motion and neural plasticity in patients with Alzheimer's disease.

Recent research has demonstrated that Alzheimer's disease (AD) affects the visual sensory pathways, producing a variety of visual deficits, including the capacity to perceive structure-from-motion (SFM). Because the sensory areas of the adult brain are known to retain a large degree of plasticity, the present study was conducted to explore whether the degradation of a visual function impaired by AD can be reversed or slowed through perceptual learning. Whereas many studies directed at learning in AD examined learning capacities involving the implicit memory system, a largely preserved system in AD, the present study focused on perceptual learning involving visual deficits impaired by AD.

Active steering along corrugated surfaces.

A study is reported of the effect of dynamic occlusion that arises during locomotion over corrugated surfaces and its facilitating role on the control of locomotion, especially in cluttered environments. Surfaces varied in degree of corrugation and type of texture. Heading accuracy was assessed by having participants perform an active steering task.

Multiple sources of information and time-to-contact judgments.

Four experiments examined how the visual system deals with multiple information sources for perceiving dynamic events. Two tau-type optical variables, one defined by the expanding object's image and the other defined by the expanding angular extent composed of the line of sight and the object's shadow, were manipulated in time-to-contact judgments. When the information specified by both variables was consistent, little perceptual accuracy was gained by having two information sources.

Perceiving curvilinear heading in the presence of moving objects.

Four experiments were directed at understanding the influence of multiple moving objects on curvilinear (i.e., circular and elliptical) heading perception.