A TUNED-TRACE THEORY OF INTERVAL-TIMING DYNAMICS

Animals on interval schedules of reinforcement can rapidly adjust a temporal dependent variable, such as wait time, to changes in the prevailing interreinforcement interval. We describe data on the effects of impulse, step, sine‐cyclic, and variable‐interval schedules and show that they can be explained by a tuned‐trace timing model with a one‐back threshold‐setting rule. The model can also explain steady‐state timing properties such as proportional and Weber law timing and the effects of reinforcement magnitude. The model assumes that food reinforcers and other time markers have a decaying effect (trace) with properties that can be derived from the rate‐sensitive property of habituation (the multiple‐time‐scale model). In timing experiments, response threshold is determined by the trace value at the time of the most recent reinforcement. The model provides a partial account for the learning of multiple intervals, but does not account for scalloping and other postpause features of responding on interval schedules and has some problems with square‐wave schedules.