Ledge and wedge: younger and older adults' perception of action possibilities

Abstract

The current study investigated whether younger (college-age) and older adults (60+ years) differ in their ability to perceive safe and unsafe motor actions. Participants decided whether to walk through openings varying in width in two penalty conditions: In the doorway condition, if participants attempted to squeeze through impossibly narrow openings, the penalty for error was entrapment. In the ledge condition, if participants attempted to inch along impossibly narrow ledges, the penalty for error was falling. Results showed that across the lifespan, people consider falling to be a more severe penalty than getting stuck: Both younger and older adults made more conservative decisions when the penalty for error was falling, and older women were especially leery of falling. In both age groups, abilities and decisions were based on dynamic properties of the body, such as compressed body size in the doorway condition and balance in the ledge condition. Findings indicate that failure to perceive possibilities for action is unlikely to be the cause of the increased prevalence of falling in older adults.

Fig. 1. Adjustable opening apparatus in (a) doorway and (b) ledge conditions. In the doorway condition, participants walked through bounded openings. In the ledge condition, participants walked along a ledge between the moving wall and a precipice

Fig. 2

Affordance function (black curve) and decision function (gray curve) fit to a typical participant's attempts and decisions, respectively, in the doorway condition. Thresholds were estimated at the 50 % point of each function. Decision error is the difference between the two thresholds. This participant's decision threshold was smaller than her affordance threshold, indicating that she attempted some openings that were too small

Fig. 3. Individual plots of participants' body dimensions and corresponding thresholds in each condition. The left panel shows static body dimensions, and the right panel shows dynamic body dimensions

Fig. 4. Decision error by sex, age, and condition. Error bars show 1 SE