Absence of a gender difference in a haptic version of the water-level task

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.

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.

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.

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

A study is reported of gender differences in a haptic version of three Piagetian tests that assess understanding of Euclidian space. A raised-line drawing kit was used both for subject responses and for production of stimuli. To test understanding of the horizontal, subjects felt pictures of a jar at four tilts and were asked to draw the water line. Two methods were used to examine understanding of the vertical. First, subjects drew a hanging electrical cord and light bulb, attached to the ceiling of a bus, parked on hills of four different angles. Subsequently, subjects drew telephone poles (represented by a single line) on hills of four different angles. In the jar task, males and females showed comparable performance, both groups showing large errors. Judgments of the vertical were very similar for males and females in the bus task, but errors diminished considerably for both genders when subjects drew telephone poles on hills. It is suggested that better judgments of the vertical in the pole task probably derive from the use of body-centered spatial reference information.

Role of gravitational cues in the haptic perception of orientation

The haptic perception of vertical, horizontal, +45 degrees-oblique, and +135 degrees-oblique orientations was studied in adults. The purpose was to establish whether the gravitational cues provided by the scanning arm-hand system were involved in the haptic oblique effect (lower performances in oblique orientations than in vertical-horizontal ones) and more generally in the haptic coding of orientation. The magnitude of these cues was manipulated by changing gravity constraints, and their variability was manipulated by changing the planes in which the task was performed (horizontal, frontal, and sagittal). In Experiment 1, only the horizontal plane was tested, either with the forearm resting on the disk supporting the rod ("supported forearm" condition) or with the forearm unsupported in the air. In the latter case, antigravitational forces were elicited during scanning. The oblique effect was present in the "unsupported" condition and was absent in the "supported" condition. In Experiment 2, the three planes were tested, either in a "natural" or in a "lightened forearm" condition in which the gravitational cues were reduced by lightening the subject's forearm. The magnitude of the oblique effect was lower in the "lightened" condition than in the "natural" one, and there was no plane effect. In Experiment 3, the subject's forearm was loaded with either a 500- or a 1,000-g bracelet, or it was not loaded. The oblique effect was the same in the three conditions, and the plane effect (lower performances in the horizontal plane than in the frontal and sagittal ones) was present only when the forearm was loaded. Taken together, these results suggested that gravitational cues may play a role in haptic coding of orientation, although the effects of decreasing or increasing these cues are not symmetrical.

Water-level representation by men and women as a function of rod-and-frame test proficiency and visual and postural information

In the water-level task, it has been repeatedly shown that, compared with men, women more often fail to represent the surface of a liquid as horizontal regardless of the tilt of the container. An attempt was made to reduce this robust gender gap through the manipulation of relevant upright references conveyed both by the position of the stimuli and the posture of the subject. It was reasoned that bringing the women to focus on such gravitational references through postural adjustment might help their performance equal that of men, thus shedding some light on the nature of the difficulty they experience in the standard setting. A lesser effect was anticipated among men. However, the results showed that, even after controlling for proficiency in the correlated visuospatial situation of the rod-and-frame test, the performance of men always surpassed that of women. Irrespective of gender, water-level representation on vertical sheets was unaffected by the subject's posture, whereas it improved when horizontal sheets were coupled with the most unstable posture. Whereas the persistence of the yet-unaccounted-for gender difference was underscored, the contributions of visual and postural cues issued at arm and full-body levels were discussed.

Women's deficiency in water-level representation: present in visual conditions yet absent in haptic contexts

The present experiment studied horizontality representation among men and women performing the water-level task either in visual conditions (the subjects saw outlines of tilted containers in which they respectively drew or set the water line) or in partially and totally haptic conditions (respectively, the subjects both saw and felt or merely felt the contours of the containers cut out of metal plates, and positioned a rod on the underside of the plates to indicate the water line). It was expected that, as the visual components of the setting were replaced by haptic ones, a reduction of the typical gender difference in proficiency would ensue. It was found that men surpassed women under visual conditions, whereas both genders were equivalent in haptic conditions. There were no gender or condition differences in a control task in which a line had to be placed horizontally in tilted containers. Forced reliance on proprioceptive cues among both men and women under the totally haptic condition was contrasted with the critical role played in visual conditions by visual references; those used by men were correct, whereas the ones used by women were incorrect.