Aging and the haptic perception of 3D surface shape

Abstract

Two experiments evaluated the ability of older and younger adults to perceive the three-dimensional (3D) shape of object surfaces from active touch (haptics). The ages of the older adults ranged from 64 to 84 years, while those of the younger adults ranged from 18 to 27 years. In Experiment 1, the participants haptically judged the shape of large (20 cm diameter) surfaces with an entire hand. In contrast, in Experiment 2, the participants explored the shape of small (5 cm diameter) surfaces with a single finger. The haptic surfaces varied in shape index (Koenderink, Solid shape, 1990; Koenderink, Image and Vision Computing, 10, 557–564, 1992) from −1.0 to +1.0 in steps of 0.25. For both types of surfaces (large and small), the participants were able to judge surface shape reliably. The older participants’ judgments of surface shape were just as accurate and precise as those of the younger participants. The results of the current study demonstrate that while older adults do possess reductions in tactile sensitivity and acuity, they nevertheless can effectively perceive 3D surface shape from haptic exploration.

Aging and Curvature Discrimination From Static and Dynamic Touch

“…The results of Experiment 1 clearly indicate that aging has significant and large effects upon the ability to discriminate surface curvature by static touch ( Figure 3); this large effect of age resembles the well-known deterioration that occurs in tactile acuity [1][2][3][4][5][6](also see Figure 4). Apparently, aging negatively affects performance for multiple static tactile tasks.…”

“…For example, tactile acuity deteriorates markedly with increases in age [1][2][3][4][5]; older adults, when performing a tactile grating orientation task, possess thresholds that are more than double (2.4 times higher than) those of younger adults in their twenties [2]. In addition, significant age-related differences in performance have been observed in a tactile letter identification task [6].…”

“…The initial groove width used for the younger participants was 3 mm. Larger initial groove widths (4 to 6 mm) were needed to determine thresholds for the older participants, because of the well known age-related deterioration in tactile acuity [1][2][3][4][5].…”

“…Tactile gratings were briefly (approximately 1.0 seconds) applied manually [2,[28][29][30] to the distal fingerpad of the index finger; the grooves of the gratings were oriented either parallel or perpendicular to the long axis of the finger. The participants' task was to judge (without vision) whether the grating's orientation was parallel or perpendicular.…”

Blindness enhances tactile acuity and haptic 3-D shape discrimination

“…Once we had found the groove widths that led to discrimination performance that was both above and below each participant's threshold, linear interpolation was used to determine the final threshold estimate (Craig & Kisner, 1998;Van Boven & Johnson, 1994). Because aging has been shown to significantly reduce tactile acuity (e.g., Norman et al, 2006Norman et al, , 2011Stevens, 1992;Vega-Bermudez & Johnson, 2004;Woodward, 1993), larger groove widths (e.g., 4-6 mm) were sometimes needed in order to determine the tactile acuities of the older participants.…”