Interference between conversation and a concurrent visuomotor task.

We report 2 experiments during which participants conversed with either a confederate (Experiment 1) or a close friend (Experiment 2) while tracking a moving target on a computer screen. In both experiments, talking led to worse performance on the tracking task than listening. We attribute this finding to the increased cognitive demands of speech planning and monitoring. Growth curve analyses of task performance during the beginning and end of conversation segments revealed dynamical changes in the impact of conversation on visuomotor task performance, with increasing impact during the beginning of speaking segments and decreasing impact during the beginning of listening segments. At the end of speaking and listening segments, this pattern reversed. These changes became more pronounced with increased difficulty of the task. Together, these results show that the planning and monitoring aspects of conversation require the majority of the attentional resources that are also used for nonlinguistic visuomotor tasks. The fact that similar results were obtained when conversing with both a confederate and a friend indicates that our findings apply to a wide range of conversational situations. This is the first study to show the fine-grained time course of the shifting attentional demands of conversation on a concurrently performed visuomotor task.