The long-term objective of the project is to identify a theory of timing that accounts quantitatively for many measures of behavior in many procedures used in the study of time perception and timed performance. Current quantitative models of timing, and variations of these models, will be specified with computer programs. These will include scalar timing theory, a multiple-oscillator theory of timing, a behavioral theory of timing, and real-time theory of conditioning. Separable parts of each of these models will be identified that correspond to perception of temporal intervals, temporal memory, and decision processes. The results of computer simulations of models based upon unique combinations of these psychological processes will be compared with experimental data from rats tested in timing tasks. To assess various hypotheses regarding temporal perception, memory, and decision processes, experiments at different scales of time involving transition between time intervals, outliers, context conditioning, and choice will be conducted. The nature of the system (deterministic or stochastic) will be assessed by examination of the time of occurrence of responses, stimuli and reinforcements using analytical methods that have been successful in the understanding of some physical and physiological systems. Complete experimental results, descriptions of models, procedures, data analysis programs will be retained in a form that can be readily used by others. Various distortions of time perception are characteristic of different psychiatric disorders and drug induced disorders. An understanding of the mechanisms underlying timed performance may contribute to an understanding of these effects.