A method for obtaining psychophysical estimates of movement costs

Although researchers generally accept the proposition that movement costs are taken into account in the planning of voluntary movements, there is no established psychophysical method for estimating such costs. The authors tested and introduce a possible method. Participants were given every possible pair of tasks from a set of tasks that varied along one or more dimensions. In each trial, they indicated which task was easier to perform. The authors used participants' probability of preferring any given task over others to estimate the judged relative cost (JRC) of that task, and they used the JRCs of all the tasks to quantify the relation between task preference and task properties. The method was applied in 3 experiments in which university students (Experiment 1, N = 20; Experiment 2, N = 40; Experiment 3, N = 20) chose which spatial target to move to in carrying an object from one position to another. The data were consistent with the hypothesis that the JRC of moving an object increases with the degree to which the object must be translated and rotated. The simplicity of the method encourages its application to a wide range of questions about motor behavior.