The prominent role of perceptual salience in object discrimination: overt discrimination of graspable side does not activate grasping affordances

Abstract

Responses to object stimuli are often faster when jutting handles are aligned with responding hands, than when they are not: handle-to-hand correspondence effects. According to a location coding account, locations of visually salient jutting parts determine the spatial coding of objects. This asymmetry then facilitates same-sided responses compared to responses on the opposite side. Alternatively, this effect has been attributed to grasping actions of the left or the right hand afforded by the handle orientation and independent of its salience (affordance activation account). Our experiments were designed to disentangle the effects of pure salience from those of affordance activations. We selected pictures of tools with one salient and non-graspable side, and one graspable and non-salient side (non-jutting handle). Two experiments were run. Each experiment had two groups of participants: one group discriminated the location of the salient side of the object stimuli; the other group discriminated the location of the graspable side of them. In Experiment 1, responses were left and right button presses; in Experiment 2, they were left and right button presses plus reach-and-grasp actions. When visual salience was removed from graspable sides, no correspondence effect was observed between their orientation and the responding hands in both the experiments. Conversely, when salience depended on non-graspable portions, a correspondence effect was produced between their orientation and the responding hand. Overt attention to graspable sides did not potentiate any grasping affordance even when participants executed grasping responses in addition to button presses. Results support the location coding account: performance was influenced by the spatial coding of visually salient properties of objects.

Motor representations evoked by objects under varying action intentions.

“…Indeed, debriefing of subjects indicated that when deciding which side of the object would be used for grasping, subjects reported that they performed the task by identifying the location of the spout. The alignment effect reported by Pellicano and Binkofski (2020) was most likely produced by spatial attention being directed toward an object’s spout. Our stimuli included a teapot with a prominent spout as well as a handle.…”

“…We now distinguish the above results from previous work suggesting that alignment effects obtained with a reach-and-grasp response do not reflect activation of motor representations, but instead are another form of spatial correspondence effect. Pellicano and Binkofski (2020) obtained no alignment effect on a reach-and-grasp response when the task-irrelevant object had no handle (asymmetry was established by the object’s spout). Two aspects of their procedure likely contributed to this outcome.…”

“…It is not surprising that after an initial response selection was made based on perceptual processing of the object, the execution of a redundant secondary response with the same hand would fail to generate an alignment effect. Second, the task used by Pellicano and Binkofski (2020) required subjects either to discern which side of the object had a spout or to determine which side would be used for grasping (i.e., the side without a spout). The only discriminative feature of the object for this task was the spout, so deciding which side would be used for grasping probably was computed by reference to the spout’s location.…”

Size coding of alternative responses is sufficient to induce a potentiation effect with manipulable objects

“…Futures researches should be specifically designed to study this temporal course and particular conditions inducing it especially considering that some studies were able to support the earlier and long-lasting nature of some potentiation effects (e.g. Pellicano, Koch, & Binkofski, 2017;Pellicano & Binkofski, 2020).…”

Event-driven proto-object based saliency in 3D space to attract a robot’s attention

“…painting a handle red). There is evidence for a bidirectional relationship between attention and affordance 30 , 31 , while other studies have shown that the correlation may not be particularly strong 32 – 34 . The relationship may be more nuanced and be affected by additional neurological systems, which would require additional study.…”