Perceiving objects by their function: An EEG study on feature saliency and prehensile affordances

• Study of the feature saliency and motor affordance effects induced by photos of objects.
• The feature saliency effect is dominant when no instruction is given.
• Premotor suppression of beta rhythm correlates with the feature saliency effect.
• EEG analysis suggests the presence of a behaviorally masked motor affordance effect.

We examined the feature saliency and prehensile/motor affordance effects that are visually elicited by a graspable object’s most salient features and graspable part, respectively. EEG was recorded from participants who attended a photo of an object, and responded to a left- or right-pointing arrow, which was overlaid on the object 1000 ms after object onset. Analysis of response times demonstrated the presence of a feature saliency effect. Lateralization of posterior alpha suppression showed that attention was initially directed to the object’s (most salient) functional end. Pre-movement frontocentral beta suppression and the modulation of the P3 component showed that a response compatible to the functional end was activated before arrow onset. Moreover, lateralization of pre-movement posterior and central alpha suppression indicated a behaviorally masked affordance effect. This suggests that the two effects may occur independently, but without specific attention orienting instructions, the feature saliency effect dominates a potential prehensile affordance effect.