Nonlinear time perception.

Sensitivity to time was investigated to test the linear-timing hypothesis. A long duration was adjusted until accuracy was 75% correct for a short duration in a two-choice procedure. Short durations (2, 4, 6, 8, 10, 12, 14, 16 and 18 s) were selected from previous research that suggests that sensitivity to time is nonlinear in this range. Rats were tested with a single short interval (Experiment 1, n=13) or a random order (Experiment 2, n=7). A local maximum in sensitivity (d' from signal detection theory) was observed at approximately 8-12 s. Sensitivity to time was reliably correlated (r's=0.759-0.941) with previous data. Weber fractions exhibited a U-shape and were negatively correlated with sensitivity to time (r=-0.800). These results provide additional evidence that sensitivity to time is nonlinearly related to physical time.