Reinforcement schedule, variable

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. 

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 addition to these differences in the types of delta agonists used, these studies also differed in numerous environmental and subject-related parameters, including 1) route of delta agonist administration (central vs. systemic), 2) schedule of reinforcement (FR < 5 vs. FR > 30), 3) use of acquisition of self-administration in drug-nai ve subjects versus maintenance of self-administration in drug-experienced subjects as a means of evaluating reinforcement, and 4) species of subject (rat vs. rhesus monkey). A better understanding of the role of these variables will require further research. Overall, results from... 

In the habit modality, response is mainly controlled by stimuli that precede rather than follow it (outcomes) (Dickinson, 1994). As a result of this, devaluation of response outcome fails to impair habit responding. Habit responding takes place as a result of exhaustive training on high ratio schedules or under variable interval schedules where reinforcement is loosely related to response (Dickinson, 1994). 

Following single 60 min VX vapor exposures in the range of 0.016 to 0.45 mg VX/m, Genovese et al. (2007) examined blood AChE activity, dose estimation by regeneration assay, transient miosis, and behavior parameters in adult male SD rats. Behavioral evaluation included a radial maze task and a variable-interval schedule-of-reinforcement task. At all concentrations tested, transient miosis and AChE activity inhibition were observed and some subjects exhibited transient ataxia and slight tremor. Following 3-month post-exposure evaluations of behavior, the authors concluded that performance deficits were minor and transient at these concentrations. Further, no delayed effects were observed. 

Figure 9 Schematic cumulative records of performance on the fixed ratio (FR), variable ratio (VR), fixed interval (FI), and variable interval (VI) schedules of reinforcement. Responses are cumulated vertically over time. Each downward deflection of the pen represents reinforcement delivery horizontal lines indicate pausing. (Reproduced from Seiden LS and Dykstra LA (1977) Psychopharmacology A Biochemical and Behavioral Approach. New York, NY Van Nostrand Reinhold.)...

Variable interval schedule delivers reinforcements after unpredictable time periods elapses... 

Variable ratio schedule delivers reinforcement after a changing number of responses... 

One approach is to find a means to reinforce the desired behaviour, preferably on a variable ratio schedule. One such example was reported from a factory in Liverpool (see Chapter 3). The introduction of a prize draw, based upon tokens collected for attendance, led to the reduction of absenteeism levels to almost zero. Other schemes have used cash bonuses for those attending on days chosen at random during the month. Both of these types of schemes use variable ratio reinforcement - one by means of a draw, the other by the random choice of the day on which attendance is rewarded. (It is worth noting that both also required attendance at the required starting time, thus also reinforcing punctuality.)... 

In general, the rules to effective enforcement are the same as the rules of schedules of reinforcement formulated by B.F. Skinner on the basis of observations of pigeons and rats the more consistent and intense (i.e., visible everywhere) the enforcement, the greater the rate of compliance the more immediate the feedback (i.e., the citation or arrest) the greater its effectiveness. These principles have been demonstrated repeatedly in many studies (e.g., De Waard and Rooijers, 1994 Shinar and McKnight, 1985). The halo effects of enforcement -both in time and in place - also follow the laws of schedules of reinforcement. Bracket and his associates demonstrated that a variable schedule of speed enforcement has longer lasting effects than a fixed schedule of daily enforcement that is abruptly terminated (Brackett and Beecher, 1980 Brackett and Edwards, 1977). 

Following FI schedule testing, each monkey was tested on another intermittent schedule, the DRL (differential reinforcement of low rate), which assessed the monkey s ability to inhibit responding. This required the monkey to wait at least 30 s before responding in order to receive a reward. Although the lead-treated monkeys were able to learn the task, they did so at a slower rate than controls and were more variable in their performance from day to day than the controls (similar to the FI results). 

Figure 4 Variability of performance (standard deviation) for number of reinforcements over the last 10 sessions of a DRL 30 s schedule of reinforcement (linear trend analysis, p = 0.003). Symbols as in Figure 2...

The manipulation of reinforcer volume in the Collier Myers (32) experiment also demonstrated the importance of one of the behavioral variables which influence the indicator response in the instrumental methodology. That is, some minimal volume of reinforcement is necessary for the instrumental response to occur at all. Larger minimal volumes are required when the schedule arranges lengthy temporal spacings of reinforcers. 

Our discussion of the Collier and Myers experiments is intended to Illustrate that when foods are evaluated with the instrumental methodology it is important to consider the role of both the behavioral variables (2 , ) and the configuration of physiological variables which the various schedules of reinforcement bring into play. 

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