| Summary: | In real life, many actions involve using one object upon the other, for instance, using a spoon to scoop from a bowl. The present thesis investigated the influence from such between object actions on affordance selection, i.e. choosing between action possibilities (affordances) provided by objects. This research question was examined by adapting a stimulus-response compatibility paradigm in the following way. Images of task-irrelevant object pairs (e.g. a spoon and a bowl) were followed by imperative central targets. Participants made speeded left/right responses to the targets, and the responses were randomly aligned with the objects. The orientation of the objects was manipulated across trials, rendering the co-location between the objects correct or incorrect for potential interactions. With this paradigm the thesis identified two behavioural effects from implied between-object actions. Both effects suggested an automatic prioritization of the affordance of the active objects (e.g. a spoon) in object pairs (e.g. a spoon and a bowl). In particular, the thesis demonstrated a novel inhibitory effect on the passive objects (e.g. the bowl). Both action-related object structures and the configuration of object pairs are critical in producing these effects. Further, online Transcranial Magnetic Stimulation (TMS) on left anterior parietal sulcus (aIPS) and left lateral occipital complex demonstrated contributions from the dorsal visual stream. In addition, altered performance of healthy older adult participants as well as patients with deficits in selective attention and response inhibition pointed towards contributions from executive functions. Distinct dynamics of the acquisition of action association between novel objects and that of affordance-selection pattern congruent with the learned action associations suggested that these effects do not depend on quickly established declarative knowledge about actions, but on slow sensorimotor-based consolidation. Collectively, the results confirmed that the implied between-object actions do affect affordance selection through sensorimotor processes. The findings reinforced the notion that vision and action is closely linked, and highlighted the need to study affordance perception not only on the object level, but also on the level of object relations and visual scenes.
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