Categorical scaling of duration as a function of temporal context in aged rats

Aged male rats at 10, 20, and 30 mo of age were trained on a 2.0 vs. 8.0-s duration bisection procedure using both auditory and visual signals and were then tested with visual signal durations in which the spacing of the intermediate signal durations was held constant as the short (S) and long (L) anchor durations were moved progressively closer to each other across blocks of sessions. Auditory clicks also preceded some trials in order to determine the potential effects of arousal and/or distraction on the timing of visual signals. The consequences of aging, reducing the S:L ratio, and auditory clicks were to increase the likelihood of observing reversals in response classifications around the geometric mean of the anchor durations. Taken together, these results suggest that the bisection "reversal effect" is dependent upon the calculation of the subjective mid-point between the two anchor durations and the differential setting of response thresholds around this category boundary as a function of temporal context.