Timberlake’s behavior systems: A paradigm shift toward an ecological approach

Theory of reinforcement schedules

The three principles of reinforcement are (1) events such as incentives and reinforcers increase the activity of an organism; (2) that activity is bounded by competition from other responses; and (3) animals approach incentives and their signs, guided by their temporal and physical conditions, together called the "contingencies of reinforcement." Mathematical models of each of these principles comprised mathematical principles of reinforcement (MPR; Killeen, 1994). Over the ensuing decades, MPR was extended to new experimental contexts. This article reviews the basic theory and its extensions to satiation, warm-up, extinction, sign tracking, pausing, and sequential control in progressive-ratio and multiple schedules. In the latter cases, a single equation balancing target and competing responses governs behavioral contrast and behavioral momentum. Momentum is intrinsic in the fundamental equations, as behavior unspools more slowly from highly aroused responses conditioned by higher rates of incitement than it does from responses from leaner contexts. Habits are responses that have accrued substantial behavioral momentum. Operant responses, being predictors of reinforcement, are approached by making them: The sight and feel of a paw on a lever is approached by placing paw on lever, as attempted for any sign of reinforcement. Behavior in concurrent schedules is governed by approach to momentarily richer patches (melioration). Applications of MPR in behavioral pharmacology and delay discounting are noted.

Sign Tracking in an Enriched Environment: A Potential Ecologically Relevant Animal Model of Adaptive Behavior Change

When an object conditioned stimulus (CS) is paired with a food unconditioned stimulus (US), anticipatory goal-directed action directed at the US location (goal tracking) is accompanied by behavior directed at the object CS (sign tracking). Sign-tracking behavior appears to be compulsive and habit-like and predicts increased vulnerability to the addictive potential of drugs in animal models. A large body of the literature also suggests that environmental enrichment protects against the development of addiction-prone phenotypes. Thus, we investigated whether compulsive-like sign tracking develops in environmentally enriched rats trained directly in their enriched home environment. We demonstrate that adolescent enriched-housed male Sprague-Dawley rats readily sign track a 5% ethanol bottle CS in their home environment and at a rate higher than adolescent standard-housed rats. We also show that enriched adolescent rats sign track less than enriched adult-trained rats and that acute isolation stress affects sign- and goal-tracking performance of adolescents and adults differently. Sign tracking increased more in the adult than the adolescent rats. Whereas the younger rats showed a decrease in goal tacking after the final stressor manipulation, the adults showed increased goal tracking. Our results are consistent with recent studies, which suggest that although sign tracking performance is compulsive-like, it is not as inflexible and habit-like as previously assumed. Testing in an enriched home environment with object CSs having greater affordance than "neutral" lever CSs may provide greater ecological relevance for investigating the development and expression of adaptive and compulsive-like behaviors in translational research.

Ecological Location of a Water Source and Spatial Dynamics of Behavior Under Temporally Scheduled Water Deliveries in a Modified Open-Field System: An Integrative Approach

It has been reported in non-contingent schedules that the variety of patterns of behavior is affected by the temporal variation of water deliveries. While temporal variation is accomplished by delivering water at fixed or variable times, spatial variation is usually accomplished by varying the number of dispensers and distance among them. Such criteria do not consider the possible ecological relevance of the location of water dispensers. Nevertheless, it is plausible to suppose that the intersection of the programed contingencies (e.g., time-based schedules), the ecological differentiated space (e.g., open vs. closed zones), and the relative location of relevant objects and events (e.g., location of the water source—peripherical vs. center zone) could set up an integrated system with the behavioral patterns of the organism. In the present study, we evaluated the eco-functional relevance of two locations of the dispensers upon behavioral dynamics in Wistar rats using fixed and variable time schedules in a modified open-field system. In Experiment 1, three subjects were exposed to a fixed time 30-s water delivery schedule. In the first condition, the water dispenser was located at the center of the experimental chamber. In the second condition, the water dispenser was located at the center of a wall of the experimental chamber. Each location was present for 20 sessions. In Experiment 2, conditions were the same, but a variable time schedule was used. Routes, distance to the dispenser, recurrence patterns, time spent in zones, entropy, and divergence were analyzed. Our findings suggest a robust differential relevance of the location of the dispensers that should be considered in studies evaluating behavioral dynamics. Results are discussed from an integrative, ecological-parametric framework.

Six clarifications for behaviour systems

The precursors of contemporary behaviour systems theory were hotly debated, and yet a similar critical fervour has not followed the second generation of behaviour systems research. I raise six items of potential or extant misunderstanding concerning behaviour systems perspectives, and attempt to set straight some of the assumptions and what motivated them, with attention to historical and theoretical context. The six challenges in focus are: 1) variety of conceptualisation of consummation; 2) potential misapprehensions about the role of general search; 3) ambiguity of predictions concerning response form; 4) ambiguity concerning what aspects are modelled as hierarchical; 5) assumptions of directedness; and 6) the relevance of spontaneous activity. For each of these six issues, some clarification is offered.