Handle-Hand Compatibility Effects for the Right and Left Hand Using Reach-to-Touch Movements

In stimulus-response compatibility tasks, performance is better when the handle of an object is oriented on the same side of the response than when the handle is oriented on the opposite side. Two major alternative accounts, the motor affordance and spatial accounts, have been proposed to explain this handle-hand compatibility effect. In two experiments, we tested between these two accounts by administering a go/no-go task to right-handed participants. Handled objects presented on a touchscreen were used as stimuli. Half of the participants had to reach-to-touch the stimuli by using their dominant hand, the other half by using their nondominant hand. Lift- off times (LTs), movement times (MTs) and spatial coordinates of the movement endpoints were recorded. Results from the LTs and MTs analyses showed no evidence of handle-hand compatibility effects. In contrast, the analyses of the spatial coordinates revealed that participants' touches were shifted more laterally towards the handle when the handles were oriented on the same side of the responding hand (Experiments 1 and 2). Furthermore, the right-hand touches landed higher (towards the handle) than the left-hand touches, especially when the vertical object dimension was particularly salient (Experiment 1). Overall, these results are in line with the activation of hand motor programs to reach and grasp the object as predicted by the motor account, at least for the right/dominant hand