Peter M. Vishton

Rule Learning by Seven-Month-Old Infants

A fundamental task of language acquisition is to extract abstract algebraic rules. Three experiments show that 7-month-old infants attend longer to sentences with unfamiliar structures than to sentences with familiar structures. The design of the artificial language task used in these experiments ensured that this discrimination could not be performed by counting, by a system that is sensitive only to transitional probabilities, or by a popular class of simple neural network models. Instead, these results suggest that infants can represent, extract, and generalize abstract algebraic rules.

Comparing effects of the horizontal-vertical illusion on grip scaling and judgment: relative versus absolute, not perception versus action.

The discovery that the prehension component of an open-loop, two-fingered reach is largely immune to certain salient pictorial illusions has been used to suggest that humans possess 2 distinct visual systems, 1 that subserves perceptual judgment and 1 that mediates visually controlled action. In this article, the authors present evidence that suggests that the critical distinction is not that of reaching and judgment but of relative and absolute perception. Experiment 1 extends the findings of S. Aglioti, J. F. X. DeSouza, and M. A. Goodale (1995) and suggests that the manual prehension component of open-loop reaching is affected by the horizontal-vertical illusion to a much smaller degree than perceptual size judgments. In Experiments 2 and 3, however, when perceptual size judgment is directed at a single element of the display, this difference vanishes. Experiment 4 demonstrates that grip scaling is strongly affected by the illusion when a single reach is scaled to both the horizontal and vertical components of a triangular figure.

Haptically Linked Dyads: Are Two Motor-Control Systems Better Than One?

Are Two Motor-Control Systems Better Than One? Kyle Reed, Michael Peshkin, Mitra J. Hartmann, Marcia Grabowecky, James Patton, and Peter M. Vishton Department of Mechanical Engineering, Northwestern University; Department of Biomedical Engineering, Northwestern University; Department of Psychology, Northwestern University; Rehabilitation Institute of Chicago, Chicago, Illinois; and Department of Psychology, College of William and Mary

Heading and path information from retinal flow in naturalistic environments

In four experiments, we explored the heading and path information available to observers as we simulated their locomotion through a cluttered environment while they fixated an object off to the side. Previously, we presented a theory about the information available and used in such situations. For such a theory to be valid, one must be sure of eye position, but we had been unable to monitor gaze systematically; in Experiment 1, we monitored eye position and found performance best when observers fixated the designated object at the center of the display. In Experiment 2, when we masked portions of the display, we found that performance generally matched the amount of display visible when scaled to retinal sensitivity. In Experiments 3 and 4, we then explored the metric of information about heading (nominal vs. absolute) available and found good nominal information but increasingly poor and biased absolute information as observers looked farther from the aimpoint. Part of the cause for this appears to be that some observers perceive that they have traversed a curved path even when taking a linear one. In all cases, we compared our results with those in the literature.

Planning to Reach for an Object Changes How the Reacher Perceives It

Three experiments assessed the influence of the Ebbinghaus illusion on size judgments that preceded verbal, grasp, or touch responses. Prior studies have found reduced effects of the illusion for the grip-scaling component of grasping, and these findings are commonly interpreted as evidence that different visual systems are employed for perceptual judgment and visually guided action. In the current experiments, the magnitude of the illusion was reduced by comparable amounts for grasping and for judgments that preceded grasping (Experiment 1). A similar effect was obtained prior to reaching to touch the targets (Experiment 2). The effect on verbal responses was apparent even when participants were simply instructed that a target touch task would follow the verbal task. After participants had completed a grasping task, the reduction in the magnitude of the illusion remained for a subsequent verbal-response judgment task (Experiment 3). Overall, the studies demonstrate strong connections between action planning and perception.

Using Kitchen Appliance Analogies to Improve Students' Reasoning about Neurological Results.

This article describes and evaluates a new technique for teaching students to interpret studies of patients with brain injuries. This technique asks students to consider how knives and blenders lose specific functionality when they are damaged. This approach better prepares students to make proper inferences from behavioral deficits observed after brain injury, specifically with reference to single and double dissociation. Significantly improved performance on multiple-choice and identification questions included in midterm examinations suggests that the impact of these thought experiments was substantive and long lasting.

Using touch or imagined touch to compensate for loss of proprioception: A case study

Proprioception is the sense of the position of ones own body. Here, we present a case study of an individual with proprioceptive loss in one limb consequent to stroke. The patient indicated that merely touching his impaired arm with his unimpaired arm temporarily restored his proprioception. We examined this claim and the effects of imagined touch by the unimpaired arm. Assessments were made using three-dimensional tracking of reaching trajectories towards targets in conditions of light and darkness. Both actual and imagined touching significantly reduced movement error and jerk, specifically for targets located in regions that both hands would be able to reach.

Infant reaching is truly predictive and based on an inertia-like principle at 6 months of age

IN ORDER TO ASSESS THE ABILITY OF 6-MONTH-OLD INFANTS TO MARE A PRINCIPLED PREDICTION ABOUT THE FUTURE MOTION OF AN OBJECT, 10 SUBJECTS WERE PRESENTED WITH A TOY MOVING ALONG 24 DIFFERENT PATHS OF OBJECT MOTION. EACH OF THESE PATHS MOVED A SMALL TOY ALONG A LINEAR TRAJECTORY AND BRIEFLY WITHIN REACH OF THE SUBJECT (SEE FIGURE). A VIDEO RECORD OF THE INFANTS WAS MADE FROM OVERHEAD AND SIDE POSITIONS, ALLOWING A RECONSTRUCTION OF THE THREE-DIMENSIONAL REACHING MOTIONS OF THEINFANTS.

Are Different Actions Mediated by Distinct Systems of Knowledge in Infancy

This chapter considers why studies of infant looking and reaching often suggest different patterns of cognitive and perceptual development. In some cases, convergent results have emerged from studies of infant looking and reaching, but differences are common. The most typical results suggest less adult-like perception and cognition in studies of reaching than in studies of looking. Several reaching studies, however, do not fit this pattern, suggesting that reaching actions may be mediated by distinct systems of knowledge and information processing. Comparisons of research on other behaviors, such as crawling and walking, also suggest that infant knowledge systems vary across actions. Research on how adult size perception differs between verbal and reaching response behaviors is considered and used as a template to interpret the developmental results. Like adults, when infants prepare to engage in particular actions, they seem to shift their sensitivity to particular sources of information and to process that information in action-relevant ways. These tendencies suggest that distinct knowledge systems mediate different actions in infancy.

How preparation to touch or grasp alters visual size perception.

Prior studies have suggested that visually guided actions are resistant to the effects of some pictorial size illusions, e.g., the maximum grip aperture component of a grasp for an element of the Ebbinghaus illusion display. We present evidence that when participants prepare to grasp, the reduction in illusion magnitude observed for action components is also present for conscious perceptual judgments. Our studies characterize how visual size perception changes when we choose to engage in different size-mediated behaviors. Even when the stimuli used were identical for two different tasks, we found that available information was processed differently. In the studies, participants always selected which of the two targets was larger. In some conditions, the context in which the targets were presented induced a visual illusion of size. We varied the sizes of target pairs to assess the magnitude of these visual illusions. In some tasks, participants indicated their size choice verbally. For other tasks, participants reached to grasp or touch the target that they perceived as larger. Illusion magnitudes were smaller when participants engaged in actions directed at a target or when participants imagined performing those actions. This shift in visual processing persisted for several minutes after participants switched back to a verbal, non-grasping, non-touch task. A motor interference task eliminated the reduction in illusion magnitude.