A comparison of simple movement behaviors across three different devices.

Reaching trajectories have provided a unique tool to observe changes in internal cognitive decisions. Furthermore, technological advances have made devices for measuring reach movements more accessible and researchers have recognized that various populations including children, elderly populations, and non-human primates can easily execute simple movements as responses. As a result, devices such as a three-dimensional (3D) reach tracker, a stylus, or a computer-mouse have been increasingly utilized to study cognitive processes. However, although the specific type of tracking device that a researcher uses may impact behavior due to the constraints it places on movements, most researchers in these fields are unaware of this potential issue. Here, we examined the potential behavioral impact of using each of these three devices. To induce re-directed movements that mimic the movements that often occur following changes in cognitive states, we used a double-step task in which displacement of an initial target location requires participants to quickly re-direct their movement. We found that reach movement parameters were largely comparable across the three devices. However, hand movements measured by a 3D reach tracker showed earlier reach initiation latencies (relative to stylus movements) and more curved movement trajectories (relative to both mouse and stylus movements). Reach movements were also re-directed following target displacement more rapidly. Thus, 3D reach trackers may be ideal for observing fast, subtle changes in internal decision-making processes compared to other devices. Taken together, this study provides a useful reference for comparing and implementing reaching studies to examine human cognition.