Visually guided pointing, the Müller-Lyer illusion, and the functional interpretation of the dorsal-ventral split: conclusions from 33 independent studies.

Models of the human vision propose a division of labor between vision-for-action (identified with the V1-PPT dorsal stream) and vision-for-perception (the V1-IT ventral stream). The idea has been successful in explaining a host of neuropsychological and behavioral data, but has remained controversial in predicting that visually guided actions should be immune from visual illusions. Here we evaluate this prediction by reanalyzing 33 independent studies of rapid pointing involving the Müller-Lyer or related illusions.

A visual-haptic Necker cube reveals temporal constraints on intersensory merging during perceptual exploration.

When viewing a three-dimensional Necker cube with one eye, participants can experience illusory reversals even while they feel the cube with their hands. This surprising property of the visual-haptic Necker cube affords a unique opportunity to investigate temporal constraints on interactions between vision and touch during extended observation of a three-dimensional object. Our observers reported reversals while they viewed the cube and, at the same time, they either held it with two-finger grips, felt it with while their hands remained stationary, or actively explored it by moving one hand.

Ames's window in proprioception.

When holding a small-scale model of Ames's trapezoidal window with the arms fully extended, several observers experience a striking proprioceptive distortion (eg one hand appears farther from the other, or one arm appears longer than the other). However, data from a matching experiment suggest that the proprioceptive misalignment of the hands is, in fact, rather less than the apparent slant of the window when this is not held. This finding argues against a 'visual-capture' account, supports an explanation in terms of bimodal integrative processes, and underscores the importance of supplementing phenomenological observations with objective measures.

Unifying sequential effects in perceptual grouping.

Temporally-extended perception involves a delicate balance of constancy and change. 'This can be seen, for instance, when viewing bistable figures such as the Necker cube. A recent study by Gepshtein and Kubovy of sequential effects in multistable dot lattices demonstrates constancy and change within the same set of data.