Figure 1.

Schematic of rate discrimination decision task and experimental setup. a, Each trial consists of a stream of events (auditory or visual) separated by long or short intervals (top). Events are presented in the presence of ongoing white noise. For easy trials, all interevent intervals are either long (left) or short (right). More difficult trials are generated by selecting interevent intervals of both values (middle). Values of interevent intervals (bottom) reflect those used for all human subjects. b, Example auditory and visual event streams for the synchronous condition. Peaks represent auditory or visual events. Red dashed lines indicate that auditory and visual events are simultaneous. c, Example auditory and visual event streams for the independent condition. d, Schematic drawing of rodent in operant conditioning apparatus. Circles are the “ports” where the animal pokes his nose to initiate stimuli or receive liquid rewards. The white rectangle is the panel of LEDs. The speaker is positioned behind the LEDs.