Movement as a window to the mind: grasping adults’ perception and understanding of others’ goal-directed movements

Did you know you are a mindreader? Most of us have a fundamental curiosity about people and are in fact engaging in the process of mindreading every day, as we navigate our social worlds. For instance, we often think about what other people are thinking. On a more basic level, we even predict others’ goals based on their actions, such as when they reach for and grasp objects in their environment. This thesis aimed to test and validate a classic action observation paradigm. In order to do so, three experiments were conducted to investigate action observation for goal-directed movements. In Experiment 1, adults' eye gaze was tracked as they viewed reach-to-grasp movements. Contrary to standard predictions, results did not replicate gaze proactivity according to a motor matching account. Rather, adults' eyes latched on to targets that were larger and/or nearer to the agent’s hand. A motor matching account would have predicted that grasp type (pincer grasp or whole-hand prehension) should cue gaze proactivity to the congruent target (i.e., small object or large object, respectively). In Experiment 2, adults’ reaction times were measured as they viewed the same stimuli, but presented in static rather than dynamic format. Similarly to Experiment 1, adults’ response times were faster to detect a target when it appeared over an object closer to the reaching hand, rather than an object farther away from the hand. Again, this was not in line with a motor matching account. Finally, in Experiment 3, adults’ explicit probability judgements were solicited for still frames taken from the original video stimuli. Yet again, a distance effect prevailed, whereby adults explicitly predicted that the agent’s hand would contact the closer of two objects, even when the hand was at rest (in the absence of any motor cue). Overall, these results imply that adults are applying non-motor heuristics during action observation. As such, the stimuli tested in these classical studies may not be fit for purpose, that is, they do not reliably show a motor matching effect during action observation in adults. The implications of these findings for future research and theorising are also discussed.