Localization of paired sound sources in the rat: small time differences

Seventeen albino rats were trained to perform two sound‐localization tasks with single and paired sound sources. The conditioned suppression of a licking response was used as a behavioral measure. All animals were first trained to detect a change from a series of single clicks on the left to a series on the right. They were then given further training with paired clicks separated by a small time interval; the discrimination was between left‐right pairs and right‐left pairs. The intervals used were 0.5, 1.0 2.0, 4.0, 8.0, 16.0, 20.0, and 32.0 msec. Five animals were given further tests with smaller values using the method of constant stimuli. Additional values tested were 31, 62, 125, and 250 μsec. Transition from single clicks to paired clicks was good for values between 0.5 and 4.0 msec. An ability to discriminate paired clicks was easily demonstrated for values between 0.25 and 16.0 msec. The upper limit for discrimination was somewhere between 20.0 and 32.0 msec. The lower limit for discrimination was between 31 and 62μsec. These results were discussed in relation to the precedence effect in human hearing.