Aging and Weight-Ratio Perception

Abstract

Past research has provided evidence that older adults have more difficulty than younger adults in discriminating small differences in lifted weight (i.e., the difference threshold for older adults is higher than that of younger adults). Given this result, one might expect that older adults would demonstrate similar impairments in weight ratio perception (a suprathreshold judgment) compared to younger adults. The current experiment compared the abilities of younger and older adults to perceive weight ratios. On any given trial, participants lifted two objects in succession and were asked to provide an estimate of the objects’ weight ratio (the weight of the heavier object relative to the lighter). The results showed that while the older participants’ weight ratio estimates were as reliable as those of the younger participants, they were significantly less accurate: the older participants frequently perceived the weight ratios to be much higher than they actually were.

Tests of the abilities to judge ratios of extensive and intensive sensory magnitudes

“…The present results agree with those of Holmin and Norman (2012): The ability of people to judge weight ratios with good accuracy may depend on judgment operations that mimic the ratio operation. Inasmuch as such mimicking operations compensate for the lack of a ratio operation, the resulting judgments might be practically equivalent to those potentially produced by the ratio operation.…”

“…Judged heaviness ratios were inaccurate, but only slightly so. The present findings that the participants judged length ratios accurately and heaviness ratios nearly accurately conform with those of the correlational studies performed by Norman et al (2017) and Holmin and Norman (2012), which were, respectively, conducted on ratios of perceived distance and ratios of the heaviness of lifted weights. Additionally, the present results show that most participants inaccurately judged ratios of perceived brightness, and that such inaccuracy was very large.…”

“…Because remembered length differed only slightly from the corresponding perceived length, the judged ratios between remembered lengths or between remembered and perceived lengths may be considered roughly equivalent to the corresponding ratios between perceived lengths. Holmin and Norman (2012) obtained data suggesting that people can judge sensory intensity ratios. They had participants lift pairs of objects and then carry out the task of judging the ratio of the heavier object weight relative to the lighter one.…”

“…The judgment accuracy found by Holmin and Norman (2012) might suggest that people are able to judge heaviness ratios. However, the following results indicated that such accuracy might derive from a judgment operation close to but different from the ratio operation.…”

Motor planning of vertical arm movements in healthy older adults: does effort optimization persist with aging?

“…Thus, the anticipation of an increased gravity torque could explain the increased directional asymmetry observed in older adults. Experiments on object weight perception in older adults have provided support for such an overestimation of gravity torque (Parikh and Cole 2012;Holmin and Norman 2012). Assuming that motor control is the result of two parallel processes, a forward model that produces accurate motor output and an optimal controller selecting the trajectories that minimize some hidden motor costs (Izawa et al 2008), over-estimating gravity torque would lead to new optimal trajectories without impeding movement accuracy .…”