AbstractObjects can be grasped in various different ways based on an actor's intended action. As such, the way in which an object is grasped can be used to infer how far in advance the movement was planned. In the current study, children ages 6 to 11, young adults, and two groups of older adults (ages 60 to 70, and ages 71+) manipulated two objects (1: glass, and 2: hammer) in two movement contexts (1: demonstration with a dowel as if it were the object, and 2: actual object use). Four actions (1: pick-up – first-order planning, 2: pick-up and use – second-order planning, 3: pick-up and pass – second-order planning, and 4: pick-up and pass for use – third-order planning) were executed to assess how the order of planning influences end-state comfort, functional grasping and beginning-state comfort in independent and joint action object manipulation. Findings support van Elk, van Schie, and Bekkering's (2014) framework for action semantics. Object manipulation involves the automatic perception and detection of affordances. With experience, the motor system is better able to anticipate the consequences of action, and thus integrate multisensory information from the environment into a movement plan. Taken in light of developmental factors, it can be argued that children shift from a reliance on previously successful movements, to consideration of affordances and task demands with improvements in multisensory integration. Likewise, with age and cognitive decline, older adults revert back to the habitual system and thus display stimulus-driven responses, as opposed to actions that reflect consideration of action demands.
Acknowledgments: The authors would like to acknowledge the Natural Sciences and Engineering Research Council, the Ontario Ministry of Training, Colleges and Universities and the University of Waterloo for funding