Figure 1.

A. Experimental Design. The timeline displays the age of hearing onset and sexual maturity for gerbils. The age range at which each experimental group was tested is shown below. Early Juveniles (blue box) were tested from P25-P40, Late Juveniles (red box) were tested from P40-P55, and Adults (gray box) were given spout training only from P25-P40 and were tested on the auditory task from P70-P85.

B. Trial Structure. A single ‘Warn’ trial is illustrated above a timeline (ms). The Pre-Trial period (1200ms) contained unmodulated noise. The trial continued only when animals remained in contact with the waterspout during >50% of the 500ms Pre-Trial Spout Check period. The Warn stimulus (AM noise at a 5Hz modulation frequency) was presented for 1000ms. During the final 100ms of the Warn stimulus, a Spout Check determined whether the gerbil was correctly off the spout (Hit) or incorrectly on the spout (Miss). A 300ms current was delivered through the waterspout immediately after the Warn stimulus as the aversive unconditioned stimulus. ‘Safe’ trials were identical in timing, although there was no AM stimulus or shock. During Safe trials, False alarms were determined from an identically positioned Spout Check interval.