Latency and frequency of responding under discrete-trial fixed-interval schedules of reinforcement

Scalar properties in animal timing: conformity and violations

The article reviews data from animal subjects on a range of timing tasks (including fixed-interval and temporal differentiation schedules, stimulus timing, aversive conditioning, and Pavlovian methods) with respect to conformity to the two scalar properties of timing behaviour: mean accuracy and scalar (Weberian) variance. Systematic deviations were found in data from temporal differentiation schedules, timing of very short (<100 ms) or very long (>100 s) durations, effects of "task difficulty", and some special cases where circadian and interval timing seemed to interact, or where some specific durations seemed to be timed more precisely than others. Theoretical reconciliation of some of these deviations with underlying scalar timing can be achieved, but a number of problematical cases remain unexplained.

Effects of d-methamphetamine on auditory and visual reaction times and detection thresholds in the baboon

Baboons were trained in both auditory and visual reaction time procedures to release a response lever in the presence of low-intensity stimuli. By varying the stimulus intensity from trial to trial, functions relating reaction time (elapsed time from stimulus onset to lever release) to stimulus intensity were established, and detection thresholds were measured. The effects of acute, IM injections of d-methamphetamine (0.001-1.0 mg/kg) were examined on these psychophysical performance baselines. Reaction times for acoustic stimuli generally were faster for higher drug doses, whereas reaction times for visual stimuli either lengthened or shortened, depending on both drug dose and individual differences among animals. Auditory thresholds were unaffected at all drug doses studied, whereas visual thresholds were generally elevated at doses of 0.1 mg/kg and above.