Dissertations, Theses, and Capstone Projects

Date of Degree


Document Type


Degree Name





Bruce L. Brown

Subject Categories



Individual Trials Analysis; Interval Timing; Memory; Peak Interval Procedure; Retention Interval; Temporal Control


A considerable body of literature on time perception has investigated the effects of short intratrial retention intervals (RI) in the seconds range, on temporal performance, however there is a dearth of research examining the effects of long, intersession RIs (hours to days range) on timing. The present study examined the effect of two different RI durations (2 days and 70 days) on time estimates in subjects on the peak interval procedure. Twenty-four rats, eight per group, were exposed to one of three conditions. The experimental group was trained at 5 months and tested after a 70-day RI. One control group was trained at the same chronological age as the experimental group and tested after a 2-day RI. The second control group was trained at 7 months and tested at the same chronological age as the experimental group. Following the RI, peak time decreased in testing when compared with peak time during training for the group exposed to the 70-day RI, but not for the two groups exposed to a 2-day RI. An individual trials analysis showed that the decrement in peak time was accompanied by a decrease in stop time but no corresponding change in start time for the long RI group. Start and stop times at testing did not vary significantly from training for either of the control groups. Variability in middle, start and stop times was found to increase significantly for the experimental group but not the control groups. The current findings can be accounted for by an increase in variability of the remembered time of reinforcement, or increased variability in start and stop thresholds of the decision mechanism of the internal clock model posited by scalar timing theory.

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