Performance in concurrent interval schedules

Four pigeons were trained under concurrent variable-interval variable-interval and fixed-interval variable-interval schedules in a two-key situation. Both response allocation and time allocation to the two schedules were measured when various reinforcement rates were arranged on each key. All animals showed an approximately constant proportional preference for the variable-interval schedule over the fixed-interval schedule. These results support Schneider's (1969) analysis of fixed-interval schedule performance.     

Observing behavior during interval schedules

Experiment 1 showed that the three stimuli associated with three chained fixed-interval links could be used to maintain observing behavior. Experiment 2 showed that three stimuli correlated with the passage of time since the last reinforcement in a fixed-interval schedule could be used to maintain observing behavior. In both experiments most observing responses occurred midway between reinforcements. Few occurred just before or just after reinforcement. Experiment 3 showed that the decline in the rate of observing behavior just before reinforcement was reduced when more stimuli could be observed. The relatively high terminal rate of observing behavior that resulted was maintained even when at least 4 sec intervened between the reinforcement and the last observed stimulus.     

Random interval schedules of reinforcement

A method for generating a reinforcement schedule that closely approximates idealized VI schedules in which reinforcement assignments occur randomly in time (RI schedules) is described. Response rates of pigeons exposed for 20 sessions to this schedule appeared very similar to response rates characteristic of arithmetic series VIs. The distribution function describing these schedules was derived and its relations to other VI distributions, as well as to FI and random ratio (RR) were shown.     

A solid-state cumulative recorder for an analog registry of accumulative events

A solid-state device for providing graphic records of various behavioral and physiological events in much the same manner as does the electromechanical cumulative recorder is described. This transistorized version of the cumulative recorder produces a noise-free (electrical and acoustical) analog cumulative record on analog recorders. The circuit provides for such features as: built-in calibrator; internal-reset oscillator; variable incremental step amplitude; and a FET op-amp to provide a constant. drift-free output level over long and extended reset periods. The output of the device can be displayed on one channel of a polygraph recorder with adjacent channels providing physiological and behavioral data to produce a real time correlation of analog and event signals.     

Steps and pips in the history of the cumulative recorder

From its inception in the 1930s until very recent times, the cumulative recorder was the most widely used measurement instrument in the experimental analysis of behavior. It was an essential instrument in the discovery and analysis of schedules of reinforcement, providing the first real-time analysis of operant response rates and patterns. This review traces the evolution of the cumulative recorder from Skinner's early modified kymographs through various models developed by Skinner and his colleagues to its perfection in the 1950s, and then into the 1960s when it proliferated as different scientific instrument companies began marketing their own models of the cumulative recorder. With the rise of digital computers, the demise of the cumulative recorder as a scientific instrument was inevitable; however, the value of the cumulative record as a monitoring device to assess schedule control of behavior continues. The cumulative recorder remains, along with the operant conditioning chamber, an icon of Skinner's approach to psychology.     

Fixed interval schedules and delay of reinforcement

In a fixed interval schedule of reinforcement the only responses to be reinforced are those made when a certain time interval has elapsed since the previous reinforcement. The behaviour of three rats on such a schedule was compared with their behaviour on a schedule where a response made at any time during the interval was reinforced by setting up a reward which was delivered when the interval had elapsed. Response rates were higher in the ordinary fixed interval schedule than in its modified version, and it is argued that this rules out attempts to explain the maintenance of fixed interval performance by delayed reinforcement. Despite the clear difference in response rates, there was considerable similarity between the post-reinforcement pauses developed in the two schedules, and this suggests that pausing is influenced more by temporal than by response contingencies.     

Optimal behavior and concurrent variable interval schedules

Behavior maintained with 2-component concurrent variable interval schedules of reinforcement (CONC VIVI) is described well by the matching law. Deviations from matching behavior have been handled by adding free parameters to the matching law equation. With CONC VIVI schedules there are infinitely many solutions to the matching law equation at each value of the procedural parameters. However, at each value of the procedural parameters, only one combination of durations of intervals spent in each VI component (dwell times) yields the combined maximum reinforcement rate. The equations that yield the optimal dwell times solution for CONC VIVI schedules are mathematically incompatible with the matching law. Optimal performance and matching coincide only when the parameter values of the two VI components are equal. It seems reasonable to use optimal behavior to assess performance in these schedules. Researchers have not compared optimal and empirical performances in CONC VIVI possibly because the equations for optimal dwell times (ODT) can be solved only numerically. We present a table of ODT for a wide range of VIs and changeover delays. We also derive a function m that can be used to compare matching data and the matching behavior predictions of optimization. We prove that 0.5<m<1.003502, and we describe some of the more nteresting properties of the function.     

Performance in concurrent interval schedules: a systematic replication

Five pigeons were trained on a variety of concurrent interval schedules that arranged reinforcements at either fixed or variable times after the last reinforcement. Two measures were obtained: the number of responses on each schedule, and the time spent responding on each schedule. Ratios of response rates on the two schedules did not equal ratios of reinforcement rates when both schedules were variable nor when one was variable and the other fixed. Ratios of times spent responding approximately equalled ratios of reinforcement rates when both schedules were variable, but did not do so when one was fixed.     

Varying reinforcement magnitude on interval schedules

In Experiment 1, rats were trained on either a random-interval or a variable-interval 60-sec schedule of reinforcement, and reinforcement magnitude was varied across conditions between one and four pellets. Although the two schedules maintained different patterns of behaviour, patterns and rates of responding were not systematically affected by the variation in reinforcement magnitude. In Experiment 2, a regulated probability interval schedule that generated similar rates of reinforcement to those of the schedules of Experiment 1 was used, with the pattern of behaviour generated resembling that typical of a random-interval schedule. Changing reinforcement magnitude again produced few systematic changes in behaviour. In Experiment 3, a variable-ratio schedule was used within a procedure that otherwise resembled that of Experiments 1 and 2. Increasing the reinforcement magnitude now decreased the rates of responding, and examination of the patterns of responding showed that this came about because rates of responding were higher early in the interreinforcer interval in the one-pellet condition. These experiments demonstrate the insensitivity of behaviour under interval schedules to changes in reinforcement magnitude and suggest the operation of mechanisms different from those engaged by ratio schedules and discretetrial learning procedures.     

A comparison of procedures for programming noncontingent reinforcement schedules

We compared two methods for programming and thinning noncontingent reinforcement (NCR) schedules during the treatment of self-injurious behavior (SIB). The participants were 3 individuals who had been diagnosed with mental retardation. Results of functional analyses indicated that all participants' SIB was maintained by positive reinforcement (i.e., access to attention or food). Following baseline, the effects of two NCR schedule-thinning procedures were compared in multielement designs. One schedule (fixed increment) was initially set at fixed-time 10-s reinforcer deliveries and was also thinned according to fixed-time intervals. The other schedule (adjusting IRT) was initially determined by participants' baseline interresponse times (IRTs) for SIB and was thinned based on IRTs observed during subsequent treatment sessions. Results indicated that both schedules were effective in initially reducing SIB and in maintaining response suppression as the schedules were thinned.     

Accuracy of performance on a matching-to-sample procedure under interval schedules

Correct matches on a matching-to-sample procedure were reinforced under fixed-interval, chained fixed-interval, and fixed-interval schedules with exteroceptive stimulus changes correlated with time since the last reinforcer (an added clock). For all four pigeons, accuracy changed within the fixed-interval and fixed-interval schedules with added clock, decreasing from the beginning of the interval to some point in the middle. The performance then became increasingly more accurate until the end of the interval. Under the chained schedules, accuracy also changed within the components. During the initial component, accuracy decreased from the beginning of the fixed interval to some point in the middle or at the end. During the middle component, the performance usually remained at an intermediate level of accuracy. During the terminal component, the initially inaccurate performance became increasingly more accurate throughout the interval. Systematic relationships between response rate and per cent error showed that all four pigeons performed most accurately at high rates. The accuracy of the performance at low rates was also quite high. These relationships held for all three types of schedules through an eight-fold variation in scheduled interreinforcement time.