Rats can discriminate between different durations of wheel running

Cart rats discriminate between short (i.e., 10 s) and long (i.e., 50 s) intervals of opportunity to run in running wheels? Eight female Long-Evans rats were exposed to 50 opportunities to run in a wheel. Following each interval, rats made a response to identify the interval. A correct response produced 0.1 ml of 15% sucrose solution, while an incorrect response caused the chamber lights to flash on and off for 5 s. Five of 8 rats met the criterion of 5 successive sessions with 80% correct responses for both durations. Furthermore, the criterion of 80% correct responses in a session was met more often with the 10-s than with the 50-s duration. Rats can discriminate between opportunities to run for different durations, but the results cast doubt on the assumption that rats are timing the intervals.