Choosing between action alternatives in an unconstrained task environment


To navigate our surroundings, the human motor system must make decisions about which path or route will be chosen. For example, a decision may need to be made between a path that has a large reach distance and shorter walking distance, or a path with a shorter reach and longer walking distance. Previous research suggests that path choices are made to minimize reach distance, as reaching is ~11 times more costly than walking a given distance (Rosenbaum et al., 2011; Rosenbaum, 2012; Cappelletto & Lyons, 2018). Furthermore, previous work from our lab provides evidence that biomechanical factors, such as joint loading, can drive cognitive decision making when choosing postures for action, quantifying this notion of "cost" (Cappelletto & Lyons, 2018). To the best of our knowledge, previous work in this area presented participants with a two-choice model, allowing only the choice between the right or the left paths. Questions remain as to how biomechanical costs and constraints are incorporated into the planning and execution of decision-making tasks with increased degrees of freedom. Sixteen female participants performed 50 trials of a bucket transfer task that varied as a function of load start position (near, middle, far, right, left), and load end position (backward, forward, right, left). Behavioural outcomes suggest that the load's start position is incorporated into the decision-making process, reflected in the participants choice of end position. Our biomechanical data also provide evidence of bottom-up processes influencing action planning, as reflected in decreased cumulative loading measures at both the shoulder and trunk.