This study tested the hypothesis that affordances for grasping with the corresponding hand are activated more strongly by three-dimensional (3D) real objects than by two-dimensional (2D) pictures of the objects. In Experiment 1, participants made left and right keypress responses to the handle or functional end (tip) of an eating utensil using compatible and incompatible mappings. In one session, stimuli were spoons mounted horizontally on a blackboard with the sides to which the handle and tip pointed varying randomly. In the other, stimuli were pictures of spoons displayed on a black computer screen. Three-dimensional and 2D sessions showed a similar benefit for compatible mapping when the tip was relevant and a small cost of compatible mapping when the handle was relevant. Experiment 2 used a flanker task in which participants responded compatibly to the location of the handle or the tip, and spoons located above and below the target spoon could have congruent or incongruent orientations. The difference between 3D and 2D displays was not obtained in the flanker effect for reaction time. There was little evidence that 3D objects activate grasping affordances that 2D images do not. Instead, we argue that visual salience of the tip is the critical factor determining these correspondence effects.

When orientation of a horizontal spoon image varies to the left or right, instructions can map left and right keypresses to the tip or handle location. We conducted Experiment 1 to determine whether practice with an incompatible mapping of the salient tip transfers to a test session in which the relevant part and/or mapping are changed. Participants performed 80 practice trials with tip-incompatible mapping, followed by 80 test trials with tip-compatible, tip-incompatible, handle-compatible, or handle-incompatible mapping. Performance improved across 20-trial blocks in the practice session. In the test session, responses were 65-ms faster with tip-compatible than tip-incompatible mapping but 31-ms faster with handle-incompatible than handle-compatible mapping. This latter result, and verbal reports, indicate that some participants adopted a strategy of responding compatibly to the salient tip even though instructed to respond to the handle. Experiment 2 focused on whether participants with handle-incompatible mapping instructions would adopt the tip-compatible strategy spontaneously or after receiving a hint. 77% of participants reported adopting the tip-compatible strategy in session 1, showing that prior experience responding to the tip is not necessary. 9% of participants did not report using that strategy in session 1 but reported changing to it in session 2 after receiving the hint. Their responses in session 2 were slower than those who used the strategy throughout, but this difference was minimal in the last two trial blocks. Compatible mapping of the salient spoon tip to keypresses dominated performance over prior practice with incompatible tip mapping and instructions with incompatible handle mapping.

No abstract