Aging and Curvature Discrimination from Static and Dynamic Touch

Abstract

Two experiments evaluated the ability of 30 older and younger adults to discriminate the curvature of simple object surfaces from static and dynamic touch. The ages of the older adults ranged from 66 to 85 years, while those of the younger adults ranged from 20 to 29 years. For each participant in both experiments, the minimum curvature magnitude needed to reliably discriminate between convex and concave surfaces was determined. In Experiment 1, participants used static touch to make their judgments of curvature, while dynamic touch was used in Experiment 2. When static touch was used to discriminate curvature, a large effect of age occurred (the thresholds were 0.67 & 1.11/m for the younger and older participants, respectively). However, when participants used dynamic touch, there was no significant difference between the ability of younger and older participants to discriminate curvature (the thresholds were 0.58 & 0.59/m for the younger and older participants, respectively). The results of the current study demonstrate that while older adults can accurately discriminate surface curvature from dynamic touch, they possess significant impairments for static touch.

Short-Term Visual Deprivation, Tactile Acuity, and Haptic Solid Shape Discrimination

“…The procedures used for determining the participants' grating orientation thresholds (i.e., their tactile acuity) were similar to those used both by ourselves [13] , [30] , [31] and others [24] , [32] , [33] , [38] . On each trial, tactile gratings were manually applied to the distal fingerpad of the index finger for one second so that the grooves and ridges of the gratings were oriented either parallel or perpendicular to the long axis of the finger.…”

Dynamic cutaneous information is sufficient for precise curvature discrimination

“…On average, older adults possess lower tactile acuity than younger adults 7 9 10 11 . For example, using a tactile grating orientation discrimination task, Norman et al 7 found that the thresholds of older adults were two to three times higher than those of younger adults. In addition, older adults have been found to perform more poorly for static curvature discrimination 7 .…”

“…In addition, older adults have been found to perform more poorly for static curvature discrimination 7 . It is therefore interesting to note that older adults frequently perform as well as younger adults for curvature or shape-related tasks where dynamic touch, or active haptic exploration, is allowed 7 9 12 13 14 . What is responsible for older participants’ good performance during active touch conditions?…”

“…7) 5 . Curvature discrimination is often better (e.g., lower thresholds) for active touch as compared to static or passive touch 6 7 8 . At the moment, it is not entirely clear exactly what information contributes to the superiority of performance that is frequently obtained during active haptic exploration.…”

“…For example, using a tactile grating orientation discrimination task, Norman et al 7 found that the thresholds of older adults were two to three times higher than those of younger adults. In addition, older adults have been found to perform more poorly for static curvature discrimination 7 . It is therefore interesting to note that older adults frequently perform as well as younger adults for curvature or shape-related tasks where dynamic touch, or active haptic exploration, is allowed 7 9 12 13 14 .…”