An exploration of limb-specific and spatial codes triggered by pictures of graspable objects




Ullrich, Emma K.

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There is much debate in the field of cognition on the nature of affordances; a concept originally invoked by Gibson (1986, as cited in Chong & Proctor, 2019) in reference to the possible actions furnished by a solid object to an embodied agent. Gibson's notion of an affordance has been substantially revised. It is now widely proposed that even images of objects automatically trigger affordances in perceptual tasks (Tucker & Ellis, 1998). Stimulus-response compatibility effects have been used to provide evidence for this claim; however, it has been repeatedly found that spatial compatibility and not anatomical compatibility contributes to these effects. This large body of evidence stands against the claim that the images of objects evoke limb-specific representations. In this thesis, I establish that specific task conditions do indeed trigger motor-based effects to an image of a graspable object with a keypress response. In a set of six experiments, participants were required to make laterality judgments via keypress responses to the image of a hand superimposed on the image of a graspable object. Our results show that participants are consistently faster when the depicted hand is the one that would be used to act on the depicted handled object, but only when they are using a spatio-anatomical frame of reference. The presence of these alignment effects demonstrates that some of our effects are limb-specific and not spatial in nature. The current set of experiments establishes results that have implications for the contemporary notion of an affordance.



Object Affordances, Motor Representations, Frames of Reference, Spatial Coding