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.

Aging and the Haptic Perception of Material Properties

“…The younger and older participants’ tactile acuities are shown in Figure 2—on average, the older adults’ grating orientation thresholds (the groove width needed to reliably discriminate the orientation of a tactile grating pressed against the fingertip) were 85.8% higher than those of the younger adults ( t (24) = 3.5, p = .002, two-tailed). This result (significantly higher thresholds, thus poorer tactile acuity for older adults) is similar to that found previously (e.g., Cheeseman et al., 2016; Manning & Tremblay, 2006; Norman et al., 2011, 2013). One can see from an inspection of Figure 2 that our younger participants’ thresholds (mean = 1.67 mm), while significantly lower than those of the older participants, were higher (on average) than the analogous thresholds for younger adults obtained in some previous studies.…”

“…First of all, there was a substantial effect of age upon the participants’ tactile acuity: On average, our older adults’ grating orientation discrimination thresholds (measured at the fingertip) were 85.8% higher than those of the younger adults (see Figure 2). The effect of age observed in the current experiment is quantitatively similar to that obtained in previous investigations (Manning & Tremblay, 2006; Norman et al., 2011, 2013; Sathian et al., 1997; Vega-Bermudez & Johnson, 2004). In addition to tactile acuity, there was a significant main effect of age with regard to haptic material recognition (see Figure 1) —the younger adults’ overall recognition accuracies were 26.5% higher than those of the older adults.…”

“…In addition to judging material properties, the participants performed a grating orientation discrimination task so that we could assess their tactile acuity. In doing this, we followed the same procedures used by Norman et al. (2013) and Cheeseman, Norman, and Kappers (2016)—successive blocks of 40 trials were run to determine the smallest groove width needed for each participant to reliably determine (i.e., discriminate with an accuracy of d ′ = 1.35) the orientation of a tactile grating (JVP Domes, Stoelting, Inc.) pressed against the distal fingerpad of their index finger.…”

“…Similar findings have occurred with respect to the sense of touch. While aging negatively affects tactile acuity (Guest, Mehrabyan, Ackerley, & McGlone, 2014; Manning & Tremblay, 2006; Norman et al., 2011, 2013; Sathian, Zangaladze, Green, Vitek, & DeLong, 1997; Stevens & Choo, 1996; Vega-Bermudez & Johnson, 2004; Wong, Gnanakumaran, & Goldreich, 2011), older adults can haptically discriminate and perceive solid shape as well as younger adults (Norman et al., 2006, 2011).…”

“…The primary purpose of the current study was to determine whether aging affects the perception of material properties. Given that the tactile acuity of older adults is reduced relative to that of younger adults (Guest et al., 2014; Manning & Tremblay, 2006; Norman et al., 2011, 2013; Sathian et al., 1997; Stevens & Choo, 1996; Vega-Bermudez & Johnson, 2004; Wong, Gnanakumaran et al., 2011), it is certainly possible that increases in age would also negatively affect the perception of material properties. Manning and Tremblay (2006) have already demonstrated that aging, with its concomitant deterioration in tactile acuity, significantly and adversely impacts tactile pattern (i.e., letter) recognition.…”