Perception of the horizontal and vertical in tangible displays: minimal gender differences

Sex differences in the haptic change task

Three experiments examined gender differences in picture location memory in the sense of touch involving the change task. In Experiments 1 and 2, blindfolded sighted participants felt 15 tangible raised-line pictures and memorized their locations for 8 min. Subsequently, they felt another set of raised-line pictures that were identical to the original set, but locations were exchanged for 6 of them. The change task required participants to indicate which raised-line pictures were moved to new locations and which were not moved. It was expected that females would show superior picture location memory compared with males. The results showed that females had a significantly higher number of correct picture location judgments than males in Experiment 1. No differences appeared between males and females on the change task when the task was much more difficult and the raised-line pictures were irregularly arrayed in the second experiment. Task difficulty was too high in Experiment 2, and a third experiment reduced the number of pictures in the irregular array to 12. Females performed better than males in Experiment 3. Gender differences in the change task are small in magnitude in touch as well as in vision. The results of the present experiments using touch are consistent with the larger literature in vision.

Perceptual learning of view-independence in visuo-haptic object representations

We previously showed that cross-modal recognition of unfamiliar objects is view-independent, in contrast to view-dependence within-modally, in both vision and haptics. Does the view-independent, bisensory representation underlying cross-modal recognition arise from integration of unisensory, view-dependent representations or intermediate, unisensory but view-independent representations? Two psychophysical experiments sought to distinguish between these alternative models. In both experiments, participants began from baseline, within-modal, view-dependence for object recognition in both vision and haptics. The first experiment induced within-modal view-independence by perceptual learning, which was completely and symmetrically transferred cross-modally: visual view-independence acquired through visual learning also resulted in haptic view-independence and vice versa. In the second experiment, both visual and haptic view-dependence were transformed to view-independence by either haptic-visual or visual-haptic cross-modal learning. We conclude that cross-modal view-independence fits with a model in which unisensory view-dependent representations are directly integrated into a bisensory, view-independent representation, rather than via intermediate, unisensory, view-independent representations.

Haptic orientation perception: Sex differences and lateralization of functions

The present study examined sex differences in haptic orientation representation using three tasks: a bimanual parallel-setting task comprising haptic orientation perception and motor matching action, and two unimanual tasks focusing on the perception and action elements separately. A verbal judgment task focused on haptic orientation perception: participants were to assign a number of minutes to a felt orientation. An orientation production task required the rotation of a bar to match a verbally presented number of minutes. Although both male and female performance was systematically biased we found that males are more accurate in parallel-setting and verbal judgment of orientation, suggesting differences in haptic orientation perception, in particular. Increasing allocentric reference frame involvement by delaying the action in the parallel-setting task did not affect the sex difference found. In addition to a male advantage over tasks, performance on both unimanual tasks suggests sex differences in lateralization of haptic orientation processing; a dependence on hand orientation was found only for right hand performance in males.

External and body-centered frames of reference in spatial memory: Evidence from touch

The study reports independent effects of external and body-centered reference cues on spatial coding of an irregular sequence of haptic locations. The aim was to investigate the nature of spatial coding by using a modality that does not provide distal cues routinely. Our method isolates and combines body-centered and external spatial reference cues for irregularly placed locations, scanned along a raised-line route. Disrupting body-centered reference for the locations, by orienting the map differently to the body in the test phase than in the presentation phase, doubled errors in positioning the locations along the route in recall. Adding external reference, by giving instructions to use a surrounding frame for reference when body-centered coding was disrupted, reduced errors to near baseline (no-rotation) levels. Adding external reference cues to intact (not displaced) body-centered reference halved errors, as compared with the baseline. The results are consistent with the hypothesis that accurate spatial coding is determined by the congruence of potential reference cues from diverse sources. The new findings suggest that external and body-centered reference cues have independent additive effects on spatial coding. The sequence of locations had a significant effect in all the reference conditions, suggesting the additional use of fortuitous but distinctive local touch cues on the route. The discussion considers theoretical and practical implications of the results.

Tactile picture perception in sighted and blind people

This paper reviews recent research on the perception of tangible pictures by sighted people and those who are blind or have extremely low vision. Raised-line pictures are useful for evaluating spatial cognition in congenitally blind people. The ease or difficulty of picture recognition is shown to vary with complexity, familiarity, and categorical information. Blind people are able to use pictorial displays effectively, but may benefit from instruction when complex depictions of three-dimensional objects involve foreshortening.

Haptic perception of the horizontal by blind and low-vision individuals

We examined haptic perception of the horizontal in visually impaired people. Blind people (late blind and congenitally blind), persons with very low vision, and blindfolded sighted individuals felt raised-line drawings of jars at four angles. They had to demonstrate their understanding that water remains horizontal, despite jar tilt, by selecting the correct raised-line drawing given four choices. Low-vision subjects, with near perfect scores, performed significantly better than the other groups of subjects. While the late-blind and blindfolded sighted subjects performed slightly better than the congenitally blind participants, the difference between the late-blind and congenitally blind groups was nonsignificant. The performance of the congenitally blind subjects indicates that visual experience is not necessary for the development of an understanding that water level stays horizontal, given container tilt.