VISUAL PERCEPTION AND ACTION IN REACHING DURING UPPER LIMB OBSTACLE AVOIDANCE

During everyday activities, people reach to specific objects with their hands and avoid obstacles. For people to move successfully through an obstacle gap, it is necessary to be able to accurately perceive the actions that the surroundings afford and adjust hand movements accordingly. Reaching behaviours, including planning (perception) and execution (action), depend on visual information. This study aimed to understand and detect the differences between perceptual judgment and actual performance of both hands during a reaching task at the time of obstacle avoidance by using a hand-scaled approach. Participants were young adults (male (n=7) and female (n=10) aged 18 to 25 years (M= 22.94, SD=1.67)) and they completed both a Perceptual Decision Task and an Action Movement Task. During the Perceptual Decision Task, participants were asked whether they perceived the need to rotate their hand or not (one hand at a time) for each of the aperture widths (0.8 to 1.4 × Hand Width) and to make a ‘yes’ or ‘no’ judgement. For the Action Movement Task, participants were instructed to move each hand through the aperture widths (0.8 to 1.4 × Hand Width). Results revealed that, participants perceived requiring hand rotations at smaller relative aperture widths, compared to when they actually rotated hands to avoid obstacles. It was also found that the dominant hand produced rotations at larger relative aperture widths than the non-dominant hand during Action Movement Task. The results of this study provide a more comprehensive understanding of how the perception-action system controls upper limb movements in young adults during an obstacle avoidance task, as well as allows a better understanding of the perception-action system for both dominant and non-dominant hands.