Given the option, people avoid incongruent responses in a dual-tasking situation.

While past work on how people can optimize dual-tasking has focused on strategic timing (i.e., when to select responses), little is known about the extent to which people can optimize dual-tasking by taking care of which responses they select. Here we test whether spatial (in)congruency influences response selection in free-choice trials. In two experiments, we combined two visual-manual tasks with spatial stimulus- and response characteristics: Participants responded to the stimulus words "left" and "right" in a forced choice task and responded "up", "down", "left" or "right" with an arrow-key to either a free choice prompt or an X located at the respective position. In Experiment 1, participants reduced the proportion of incongruent pairs of responses (i.e., left in one and right in the other task). In Experiment 2, we found that such flexibility in response selection also holds in more constrained environments: Within runs of four trials the free-choice options were continuously reduced based on the responses already given. The combined results of Experiments 1 and 2 suggest that response selection in free choice trials is driven by performance optimization beyond response conflict.