The effect of object orientation as a function of affordance on motor action priming


Physical property affordances (PPA's) are characteristics of objects that have been suggested to prime motor interactions with that object by encompassing action relevant features and orientations within their physical makeup (Ellis & Tucker, 2006). Previous work, employing stimulus-response paradigms has shown that simple reaction time (SRT) is facilitated when response effectors are aligned spatially with the presented PPA, but questions remain as to the degree to which these priming benefits are mediated by varying orientations of the same object. In this study, participants were presented images of a coloured 3-dimensional pole that varied in either vertical, horizontal or orthogonal orientation. Stimulus colour was used to define two mapping conditions (blue/right, yellow/left & blue/left, yellow/right) that cued participants as to hand of response. Apart from colour, the characteristics of the pole in all orientations was identical. SRT's were calculated as the time from stimulus onset to button depression. Results indicate significantly shorter SRT's when the right arm was aligned with the direction of the pole, such that it could be grasped in a way that was anatomically optimal, thereby mitigating energy expenditure and excessive pronation and supination of the hand. SRTs for all other pole orientations were not different from each other. These results suggest that affordance universality may be linked to laterality and that these laterality effects are particularly robust with lateral preference. Future directions of this research will use EMG to assess potential pre-motor activation time as a function of affordance orientation.