Schedules reinforcement

The differing effects of various schedules of reinforcement can be seen if we consider two situations. In the first we are trying to encourage someone (including ourselves) to increase the frequency of a new behaviour or pattern of behaviour. In such a situation, where a new skill is being learnt, it is probably most effective to reinforce their successful attempts every time 

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However, reinforcement does not necessarily happen all the time or even regularly. For example, even though many of us work every day, we do not necessarily get paid at the end of that day for what we did. And in some instances reinforcement is unpredictable, like when you receive an unexpected phone call that is rewarding to you from a close friend. When reinforcement doesn t occur in a predictable way, it is referred to as being on a variable or intermittent (random or unpredictable) schedule (or pattern). Behavioral researchers have found that a variable reinforcement schedule produces behavior patterns that are much more difficult to change than behavior patterns reinforced regularly. 

Chaudhri N, Caggiula AR, et al (2007) Self-administered and noncontingent nicotine enhance reinforced operant responding in rats impact of nicotine dose and reinforcement schedule. Psychopharmacology 190(3) 353-362... 

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. 

Experiments are conducted in commercially available operant chambers (Coulboum Instruments, Allentown, PA 18106, USA), equipped with two response levers, a food hopper and receptacle, stimulus lights and an exhaust fan. Male rats (225-250 g) are housed individually and maintained under a non-inverted 12/12 hr light/dark cycle with restricted access to food (15 g per day). Lever training begins under a continuous reinforcement schedule of food presentation. Daily sessions are terminated after 1 hour or 50 food presentations, whichever occurs first. Subsequently, the response requirement is increased by one response per daily session up to FR5. Once rats receive 50 food pellets in a single session under the FR5 schedule (typically within 5 days), food training is suspended and... 

Gray T, Wise RA (1980) Effects of pimozide on lever pressing behavior maintained on an intermittent reinforcement schedule. Pharmacol Biochem Behav 72 931-935. 

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. 

A mixed schedule of reinforcement is identical to a multiple schedule of reinforcement, except that there are no external stimuli provided to the subject to indicate that the operative reinforcement schedule has switched. Thus, the only indication to the subject as to what pays off is the feedback it receives from its own behavior. This minimizes the extent of stimulus control over behavior relative to that of a comparable multiple schedule of reinforcement. 

The appetitive aspect of food intake is more specifically assessed by operant food-reinforced behavior. De Vry et al. (70) suggest that a short-duration reinforcement schedule (10 min, fixed ratio 1—operant food reinforcement) is especially sensitive to the appetitive process. 

After initial shaping to press the correct lever for food reinforcement, rats are trained to achieve a stable baseline of operant behavior on the predetermined reinforcement schedule (70). 

Using a 30-min fixed ratio 15 (FR 15) reinforcement schedule, both the CBi receptor W1N55,212 and the CBi receptor antagonist SR141716 dose-dependently suppressed response rate (71) (see Note 11). 

Another IVSA procedure is the progressive ratio reinforcement schedule, which compels increasing lever presses from the animals before an intravenous dose is released via self-administration. This procedure enables to define the... 

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