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Richard Wilkie, Rachael Raw, Georgios Kountouriotis, Mark Mon-Williams; Age differences negotiating paths of different widths at different speeds: does old age mean “middle of the road”?. Journal of Vision 2011;11(11):916. doi: 10.1167/11.11.916.
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Skilled movements deteriorate with increased age for well-documented physiological reasons. Reduced sensory sensitivity and biomechanical attenuation can interfere with motor function making older adults more variable in their responses. We examined the degree to which older adults manage to compensate for this increase in visual-motor variability when carrying out two skilled actions: tracing and steering. In both cases, participants generated trajectories within the boundaries of a delineated path. When tracing, the participants used a handheld stylus to follow a sinusoidal shape displayed on a tablet laptop. When steering, participants used a steering-wheel to change their locomotor direction to match a perspective-correct computer-generated sinusoidal roadway (see Wilkie & Wann, 2003). Three different path widths were used (2, 4 or 6 mm in tracing; 2, 4 or 6 m in steering), as well as two speeds (slow was half the fast speed). In the tracing task participants could also move at their preferred speed on 1/3 of trials. Older participants were more variable but compensated for their increased motor variability by being slower (when possible) and staying further away from the road edges (i.e. sticking to the “middle of the road”). This meant that although on wider paths the older participants were able to meet the task requirements (stay within the boundaries) on narrow paths their performance deteriorated (especially at fast speeds). In contrast, the young were able to be more accurate on narrow paths whilst moving faster and cutting corners on wide paths (presumably as a function of their lower variability). Our results show that compensation strategies generalise across two different visual-motor tasks (tracing to steering) and reveal fundamental mechanisms underlying skilled performance in the human action system.
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