Abstract
Previous research on visual-haptic cross-modal shape matching has typically investigated the abilities of younger adults (e.g., Gibson, 1962, 1963; Norman, Norman, Clayton, Lianekhammy, & Zielke, 2004). Aging is known to lead to deteriorations in both tactile acuity (e.g., Stevens, 1992) and the visual ability to detect and discriminate 3-D shape (e.g., Andersen & Atchley, 1995; Norman, Dawson, & Butler, 2000; Norman, Clayton, Shular, & Thompson, 2004). The purpose of our study was to evaluate whether and to what extent these visual and tactile deteriorations compromise older observers' abilities to cross-modally compare 3-D shape across vision and haptics. Ten younger (<= 22 years) and ten older (64–81 years) observers participated in the experiment. On each trial, the observers haptically explored one of 12 naturally-shaped objects for 7 seconds; they were then required to indicate which of the 12 simultaneously visible objects possessed the same shape as the one they had haptically explored. Each observer performed a total of 96 cross-modal shape comparisons (8 repetitions for each of the 12 objects). Observers in both age groups performed well above chance levels, but made systematic errors that suggested that their matches were based upon similarities in the objects' global shapes. The performance levels of the younger observers were about 60 percent higher than those of the older observers (the mean performance of the younger observers was 67.6 percent correct, while that obtained for the older observers was 42.4 percent). In addition to their overall better performance, the younger observers also exhibited higher rates of improvement over time with the task than did the older observers. The reduced performance of the older observers did not correlate with the reductions observed in their visual and tactual acuities. The results thus suggest that the age-related deficit in cross-modal shape matching is caused by central rather than peripheral factors.