Trajectory Effects in a Novel Serial Reaction Time Task

The serial reaction time (SRT) task, which measures how participants’ keypress responses speed up as a repeating stimulus sequence is learned, is popular in implicit and motor learning research, and may help us understand the basic learning mechanisms underlying the acquisition of complex skills (e.g., riding a bike). However, complex action sequences are not simple stimulus-response chains, but rather require representing sequential context in order to learn. Moreover, human actions are continuous, temporally-extended movements that are not fully measured in the discrete button presses of the SRT task. Using a novel movement adaptation of the SRT task in which spatial locations are both stimuli and response options, participants were trained to move the mouse cursor to a continuous sequence of stimuli. We replicate the Nissen and Bullemer (1987) RT results with the trajectory SRT paradigm and show sequential context effects–predictive bends in response trajectories–that promise to reveal cognitive processes underlying sequential action learning.