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Models of interval timing typically include a response threshold to account for temporal production.  The present study sought to evaluate the dependent concurrent fixed-interval fixed-interval schedule of reinforcement as a tool for selectively isolating the response threshold in rats, pigeons, and humans.  In this task, reinforcement is available either at one location after a short delay or at another location at a longer delay. Because the reinforced location is not signaled, subjects normally respond on the first location and, if reinforcement is not delivered, then switch to the second location.  The latency to switch between locations served as the primary dependent measure.  After training rats, pigeons, and humans with equal reinforcement magnitudes in the short and long delays, the magnitude of reinforcement was increased threefold on the long-delay location. Consistent with model predictions, this biasing procedure decreased estimates of the response threshold of rats and pigeons, but also reduced temporal control in these species and increased response-threshold estimates in humans.  Human and pigeon performance also suggested a magnitude-induced increase in the speed of the internal clock.  Collectively, these results suggest that differences in reinforcement magnitude between response alternatives appear to modulate the response threshold, but not selectively, and may provide guidance for better isolating response-threshold effects in humans.

Operant behavior can reflect the influence of goal‐directed and habitual processes. These can be distinguished by changes to response rate following devaluation of the reinforcing outcome. Whether a response is goal directed or habitual depends on whether devaluation affects response rate. Response rate can be decomposed into frequencies of bouts and pauses by analyzing the distribution of interresponse times. This study sought to characterize goal‐directed and habitual behaviors in terms of bout‐initiation rate, within‐bout response rate, bout length, and bout duration. Data were taken from three published studies that compared sensitivity to devaluation following brief and extended training with variable‐interval schedules. Analyses focused on goal‐directed and habitual responding, a comparison of a habitual response to a similarly trained response that had been converted back to goal‐directed status after a surprising event, and a demonstration of contextual control of habit and goal direction in the same subjects. Across experiments and despite responses being clearly distinguished as goal directed and habitual by total response rate, analyses of bout‐initiation rate, within‐bout rate, bout length, and bout duration did not reveal a pattern that distinguished goal‐directed from habitual responding. [ABSTRACT FROM AUTHOR]

In nonhuman animals, the transitive inference (TI) task typically involves training a series of four simultaneous discriminations involving, for example, arbitrary colors in which choice of one stimulus in each pair is reinforced [+] and choice of the other color is nonreinforced [−]. This can be represented as A+B−, B+C−, C+D−, D+E− and can be conceptualized as a series of linear relationships: A > B > C > D > E. After training, animals are tested on the untrained non-endpoint pair, BD. Preference for B over D is taken as evidence of TI and occurs because B is greater than D in the implied series. In the present study we trained pigeons using a novel training procedure-a hybrid of successive pair training (training one pair at a time) and mixed-pair training (training all pairs at once)-designed to overcome some of the limitations of earlier procedures. Using this hybrid procedure, we trained five premise pairs (A+B−, B+C−, C+D−, D+E−, and E+F−) which allowed us to test three untrained non-endpoint pairs (BD, CE, and BE). A significant TI effect was found for most subjects on at least two out of three test pairs. Different theories of TI are discussed. The results suggest that this hybrid training is an efficient procedure for establishing mixed-pair acquisition and a TI effect. [ABSTRACT FROM AUTHOR]

• Motivated behavior comprises sequences of actions organized within nested states. • This organization is represented as a nonstationary partially hidden Markov model. • The model balances parsimony, fidelity to the behavior systems approach and to data. • The Markov model formulates quantitative, verifiable behavioral predictions. • Refinements in model architecture, applicability, and methodology are identified. The behavior systems framework suggests that motivated behavior—e.g., seeking food and mates, avoiding predators—consists of sequences of actions organized within nested behavioral states. This framework has bridged behavioral ecology and experimental psychology, providing key insights into critical behavioral processes. In particular, the behavior systems framework entails a particular organization of behavior over time. The present paper examines whether such organization emerges from a generic Markov process, where the current behavioral state determines the probability distribution of subsequent behavioral states. This proposition is developed as a systematic examination of increasingly complex Markov models, seeking a computational formulation that balances adherence to the behavior systems approach, parsimony, and conformity to data. As a result of this exercise, a nonstationary partially hidden Markov model is selected as a computational formulation of the predatory subsystem. It is noted that the temporal distribution of discrete responses may further unveil the structure and parameters of the model but, without proper mathematical modeling, these discrete responses may be misleading. Opportunities for further elaboration of the proposed computational formulation are identified, including developments in its architecture, extensions to defensive and reproductive subsystems, and methodological refinements. [ABSTRACT FROM AUTHOR]