Functional Autonomy Affects Elderly Spatial Perception in Body-Centered Coordinates

Abstract

According to the action-specific theory of perception, a person's dynamic ability to act in the environment affects her/his spatial perception. Empirical evidence shows that the elderly perceive distances as farther compared with younger adults and that the harder the ground surface to walk, the farther the perceived distance. Such results suggest a general perceptual readaptation promoted by the aging process that is fine-tuned with the decline of the motor resources. However, it is still unknown whether the elderly space perception is affected by interindividual differences in their functional autonomy (FA) and whether the decline of motor resources affects spatial categorization only when distances are judged with reference to the observer's own body or also when they are judged with reference to the body of another agent present in the scene. To this aim, a sample of elderly adults with preserved cognitive functions but different levels of FA, measured through the Instrumental Activity of Daily Living (IADL) scale, were enrolled and tested on the extrapersonal space categorization task. This task requires judging the position of a target as "Near" or "Far" with respect to different reference frames (RFs): centered on the observer's body (Self RF) or centered on external elements, like another body (Other RF) or an object (Object RF). Results indicated that the higher the level of FA, the wider the space categorized as "Near" when adopting as reference frame our own body or the body of another agent in the scene, but not a static object. In conclusion, the individual functional autonomy of elderly individuals, which is strongly influenced by motor resources and efficiency, modulates how the surrounding space is represented, but only when the distance judgment implies an agent body, thus providing new relevant data for recent embodied cognition models of aging.

Figure 1

Exemplar stimuli and series used in the experiment. RF = reference frame. (a) Egocentric Self RF; (b) allocentric Other RF; (c) allocentric Object RF. (d) Hypothetical example of an ascending series for the Self RF. From left to right, pictures are presented until the participant changes his/her judgment from “Near” to “Far”. Picture shows distances 10–16 m in steps of 2 m but the ascending series started always at 2 m. (e) Hypothetical example of a descending series for the Self RF. As for (d), pictures are presented until the participant changes his/her judgment from “Far” to “Near”. Picture shows distances 16–10 m in steps of 2 m but the descending series started always at 54 m.

Figure 2

Regression analyses results. Scatter plot and corresponding regression lines for the relationship between the dependent variable mean Judgment Transition Threshold (JTT) referring to the three different RFs (Self, Other, and Object) and the independent variable IADL (Instrumental Activities of Daily Living) percentage scores.