Objects processing in perception and action: From location and action coding to affordances

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Objects are means by which humans relate to, modify and create their environment. Properties of single and paired objects provide cues to our perceptual and motor system that affect the efficiency of our performance. Spatial orientation of single objects is one of such cues: motor responses of left/right hands are typically faster and more accurate when they correspond to objects orientations (object-based Correspondence Effects-CEs). Two alternative accounts are proposed for this effect, based on the source of such spatial orientation. The location coding account states that object asymmetries, generated by protruding portions like handle or goal-directed sides (e.g. left or right), become salient to the observer and automatically activate generic motor responses of the corresponding hand. The affordance activation account instead states that objects activate appropriate manipulative actions of the hand aligned with the handle, whether visually salient or not. Recently, I formulated an action coding account specifically for CEs obtained with paired objects, since the location coding was insufficient to explain the observed effects. Thus, an action-direction code is formed for consistent object pairs (e.g. jug+cup), but is missing when object pairs share no relation at all (jug+ball). Consequently, CEs are only produced in the former case. My studies contributed to reduce the impact of the affordance activation through evidence supporting the location coding account. However, which process precisely governs our interaction with objects is still a matter of debate. In addition, my new action coding proposal calls for further investigation. My project foresees to test in parallel the current accounts of CEs and their underlying processes in three WPs: WP1, in two behavioral experiments, tackles the effects of action relations between accurately selected objects’ pictures, with and without the contribution of semantic relations. WP2, with one fMRI experiment, investigates the way action and semantic links between objects are processed in the brain and to what extent their activation patterns coincide or mismatch. To do so, innovative computational approaches (multivariate pattern, predictive pattern decomposition analyses) are combined. In WP3, five behavioral experiments are run including: real objects and their pictures (single and paired), distal and proximal responses (button press and grasp), reach-and-grasp responses with and without physical obstacles. Here, I will assess the effect of increasingly realistic contexts on the interaction with objects, and test the possibility that position-action coding gives the way to the affordance process. In sum, my project aims at finding exhaustive answers as to whether: the affordance activation account is still valid, net of conflicting evidence; the location-action coding account is likely to prevail; the processes coexist to some extent and a dividing line must be established.