The unimanual handle-to-hand correspondence effect: evidence for a location coding account

The handle-to-hand correspondence effect refers to faster and more accurate responses when the responding hand is aligned with the graspable part of an object tool, compared to when they lay on opposite sides. We performed four behavioral experiments to investigate whether this effect depends on the activation of grasping affordances (affordance activation account) or is to be traced back to a Simon effect, resulting from the spatial coding of stimuli and responses and from their dimensional overlap (location coding account). We manipulated the availability of a response alternative by requiring participants to perform either a unimanual go/no-go task (absence of a response alternative) or a joint go/no-go task (available response alternative) and the type of response required (button-press or grasping response). We found no handle-to-hand correspondence effect in the individual go/no-go task either when a button-press (Experiment 1A) or a grasping (Experiment 2A) response was required, whereas a significant effect emerged in the joint go/no-go task, irrespective of response modality (Experiments1B and 2B). These results do not support the idea that complex motor affordances are activated for meaningful objects, but are rather consistent with the more parsimonious location coding account.