Simple reinforcement schedules

The second parameter (number of responses per session) provides an estimate of the effects of the test substance on operant performance. If the test substance exerts marked sedative effects, the number of responses would normally be decreased. Response rate could even be increased if the test substance possessed psychostimulant effects. Interpretation of drug effects on operant performance is, however, not simple, because other factors can contribute to effects of the test substance on response rate. In the present procedure, where the effect of the reinforcement schedule (FRIO) is to produce a high rate of baseline responding, test substances with either sedative or psychostimulant effects will generally decrease the rate of responding. 

Consequence stimuli can occur on the basis of time elapsing or on the basis of the number of responses that have occurred or both. In the human environment, schedules of reinforcement exhibit a remarkable complexity. For the purposes of understanding how these various reinforcement schedules or payoff schemes control the frequency and the pattern of behavior in time, simpler versions were initially studied in a laboratory context. As the understanding of simple reinforcement schedules evolved, increasingly complex schedules that more closely mimicked the human environment were elaborated and examined in laboratory experiments. 

There are four simple schedules of reinforcement the fixed interval (FI) and the variable interval (VI), both of which are temporally based reinforcement schedules, and the fixed ratio (FR) and the variable ratio... 

In the other two simple reinforcement schedules, reinforcement availability is based on the number of occurrences of the designated response. On an FR schedule, the completion of the number of responses specified by the schedule parameter value is required for each reinforcement delivery. An FR 100 schedule, then, requires 100 occurrences of the designated response for reinforcement delivery. The classic examples of FR schedules are the piecework systems that operated in factories early in US history, where workers were paid for each piece or unit they produced. The FR schedule generates its own characteristic behavior pattern which consists of a pause or period of no responding after each reinforcement delivery, followed by an abrupt transition to a very rapid rate of responding - a pattern known as break and run and shown in Figure 9. 

The means by which an investigator gains latitude in arranging his test situation is through the use of schedules of reinforcement which evolved from B. F. Skinner s early attempts to study the eating behavior of rats (30 21) - The distinguishing feature of a schedule of reinforcement is that it imposes a criterion which must be met before the animal s response can produce the food-consequence (3 ). We will discuss the criteria which constitute the simple reinforcement schedules below, and then will Illustrate how these simple schedules can be put to use in evaluating foods. 

Before closing this discussion of simple reinforcement schedules we wish to make a brief comment on the ratio schedules. 

Intermittent schedules may also be maintained by negative reinforcement, usually by a brief mild electric shock. The most popular of these is continuous or Sidman avoidance in which each response postpones a shock by a fixed amount of time. By spacing its successive responses within this time interval, the animal may postpone shock indefinitely. This schedule is particularly useful as a comparison to behavior generated by positive reinforcement if a toxicant is suspected of producing anorexia. Simple intermittent schedules such as these have been used fairly widely in behavioral toxicology and have proved to be sensitive to the effects of a number of industrial and environmental toxicants. 

Risks Earlier we worked through a simple four-step risk analysis process. To reinforce the need for at least a rudimentary risk analysis, consider the observation of Nassim Taleb (2007) The unexpected almost always pushes in a single direction higher costs and a longer time to completion. He cites an admittedly extreme example. The Sydney Opera House, which was originally projected to cost AU 7 million, opened ten years late, and ended up costing AU 104 million. On the Boston Artery project in the U.S., final costs were twice the initial estimate (Wikipedia 2011). The point If you are careless with risk analysis, those risks, when they occur, are much more likely to add to—not reduce—your costs and expand—not contract— your schedule. Perhaps you should build a cushion into your Milestones/Schedule. 

Figure T summarizes some aspects of concurrent VI VI schedules which are important for the present discussion. The top panel illustrates that when both schedules are identical in length and both produce identical foods the sequence of responses is likely to approach a simple alternation pattern. In fact, the animal can maximize the number of reinforcers it obtains per unit time by alternately "checking" in this way whether the VI schedule on each disc is ready to provide a reinforcer. While this is an efficient way for the bird to precede, and yields a preference ratio of approximately 0.5 (which would be expected if, in fact, the bird is indifferent to the two identical foods), this alternating pattern of responding proves not to be optimal when foods with different properties are compared. Consequently, it is...

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