Fig. 1.

Trial configuration. Trials began with an auditory instruction (spoken phrase, “hold attention” or “switch attention”) spoken by the target speaker (male or female voice from the left side or the right side). 1500 ms after the cue onset, two simultaneous auditory streams began, with a 600 ms gap between the first and second words. In the maintain trial depicted above (solid line), subjects would hear “hold attention” in a male voice from the left or right side, attend to the male voice throughout the trial and repeat back, “headphones, football.” In the switch trial depicted above (dashed line), subjects would hear “switch attention” in a male voice from the left or right, attend to the male voice for the first word, then switch attention to the female voice for the second word and repeat back, “headphones, headlight.”