A hardware random number generator for use with computer control of probabilistic contingencies

A solid-state random number generator is described, which uses the leakage across a reversed biased diode as the random source. Statistical tests carried out on sequences of numbers failed to show any biases from randomness at sampling rates up to 3 kHz.     

Opioid-reinforced operant behavior: selective suppression by alpha-methyl-para-tyrosine.

Morphine-addicted rats performed operant responses for opioid or milk rewards. When rats were then denied access to opioids, abstinence symptoms developed. Responding under extinction conditions 2 wk. after opioid withdrawal provided a measure of the "relapse" tendency. Systemic administration of DL-alpha-methyl-para-tyrosine, an inhibitor of catecholamine synthesis, suppressed these responses if they had been reinforced by an opioid but not if they had been established with milk reinforcement. This indicates that the integrity of the catecholamine systems is vital for relapse to occur.     

A computer-oriented system for high-speed recording of operant behavior

A method is described by which large quantities of data, generated at high and variable rates from a large number of test boxes, are recorded on a single eight-channel punched paper tape. The data, which include a record of the occurrence time of each event in 1/10-sec units, are in a compact form, suitable for conversion to standard Hollerith punched card codes and for decoding and summarizing by a large digital computer. Experience with the system has demonstrated a high degree of accuracy and reliability, and low operating cost.     

Some effects of methylphenidate on stimulus control of ratio avoidance behavior in the rat

After exposure to an avoidance schedule which included a warning signal, a rat was placed on a multiple schedule in which the first component was the same as before, i.e., a single response reset the response-shock interval, delaying shock, and the second component differed only in that four bar-presses were required to postpone shock. A fixed ratio requirement of four responses (FR 4) generated behavior resembling a fixed ratio requirement of one response (FR 1) since responding was controlled by the warning signal but more shocks were received. At a dosage of 2 mg/kg, methylphenidate given intraperitoneally decreased shock frequency during FR 4 periods while FR 1 behavior was not affected; at 4 mg/kg, stimulus control of avoidance responding was impaired during both components. Results at 4 mg/kg were partially confirmed by two animals exposed to an FR 4 avoidance schedule which included a warning signal but with different parameters. Response distributions showed that methylphenidate increased response rates in the absence of the warning signal, i.e., stimulus control of ratio-avoidance behavior was impaired although the increased response rates reduced shock frequency. One hour later responses again occurred more frequently during the signal than in its absence but shocks were less frequent than during control (non-drug) periods.     

A device for presenting attack opportunity as a reinforcer for operant behavior

A device is described which automatically measures barpresses reinforced by short opportunities to attack male mice. Data on barpress rates indicate rapid and reliable acquisition of preferences for reinforcer bars and rapid abolition of this preference when the reinforcement contingency is subsequently eliminated. The data are less reliable for reversal learning.     

A rapid automatic technique for generating operant key-press behavior in rats

Experimentally naive rats were trained to key press on a fixed-ratio 10 schedule of food reinforcement by a completely automatic procedure within a single, 1-hr session. Control procedures demonstrated that the resulting behavior was an operant, under control of the schedule of reinforcement and the specified reinforcing stimulus (food). A simple, combination food-tray operandum, also described, was used as the basis for the training technique.     

A simple stimulus generator for evoked response studies

An inexpensive computer-driven bipolar stimulator is described. The device produces variable-duration bipolar click stimuli for use in auditory evoked response studies, but is applicable to other research. The unit is driven directly from the digital input/output interface of the averaging computer, and temporal parameters are completely controlled by the machine.     

A bite manipulandum for the development of operant behavior in predacious fishes

An inexpensive bite manipulandum is described for use in operant conditioning studies with predacious fishes such as the largemouth bass. Compression of a rubber nipple by a fish bite is transduced by a mounted phonograph speaker. The use of the fish’s natural foods as rein-forcers in conjunction with this device makes it possible to obtain schedule-of-reinforcement data not previously obtainable with this species. Sample interval and ratio data are provided.     

Social reinforcement of operant behavior in rats: a methodological note.

An apparatus was developed to study social reinforcement in the rat. Four Long-Evans female rats were trained to press a lever via shaping, with the reinforcer being access to a castrated male rat. Responding under a fixed-ratio schedule and in extinction was also observed. Social access was found to be an effective reinforcer. When social reinforcement was compared with food reinforcement under similar conditions of deprivation and reinforcer duration, no significant differences were observed.     

Reliable operant apparatus for fish: Audio stimulus generator, response button, and pellet-dispensing nipple

As part of ongoing research into the ability of koi to categorize complex auditory stimuli, we have had to develop novel apparatus. The stimulus generator presents sound from two CD drives under computer control through a new underwater speaker. The operant manipulandum is a horizontal button that eliminates spurious triggering by water turbulence and problematic response topographies. The button’s design has also been adapted for use by tilapia in an aquacultural food-preference study. The feeder uses a nipple to dispense food pellets reliably under water. In this paper, the apparatus is described in detail. Also discussed are methodological issues related to its design, as well as its usage in a pilot study in which koi learned to discriminate music from silence by using a single manipulandum with food reinforcement.     

Response persistence: the effects of stimulus control on negatively reinforced problem behavior in a concurrent operant

In the context of instructional demands, compliance and problem behavior can be considered concurrent operants. Of applied interest is increasing one response (i.e., compliance) while decreasing the other (i.e., problem behavior). Strategic arrangement of reinforcement can alter response allocation accordingly. Such schedules can also influence response persistence and generalization. A case study is used to illustrate the effects of stimulus-reinforcer relations in a concurrent-operants arrangement involving an adult with developmental disabilities and problem behavior. Results are discussed in the context of basic operant research findings in the areas of stimulus control and behavioral persistence.     

Response acquisition under targeted percentile schedules: a continuing quandary for molar models of operant behavior.

The number of responses rats made in a "run" of consecutive left-lever presses, prior to a trial-ending right-lever press, was differentiated using a targeted percentile procedure. Under the nondifferential baseline, reinforcement was provided with a probability of .33 at the end of a trial, irrespective of the run on that trial. Most of the 30 subjects made short runs under these conditions, with the mean for the group around three. A targeted percentile schedule was next used to differentiate run length around the target value of 12. The current run was reinforced if it was nearer the target than 67% of those runs in the last 24 trials that were on the same side of the target as the current run. Programming reinforcement in this way held overall reinforcement probability per trial constant at .33 while providing reinforcement differentially with respect to runs more closely approximating the target of 12. The mean run for the group under this procedure increased to approximately 10. Runs approaching the target length were acquired even though differentiated responding produced the same probability of reinforcement per trial, decreased the probability of reinforcement per response, did not increase overall reinforcement rate, and generally substantially reduced it (i.e., in only a few instances did response rate increase sufficiently to compensate for the increase in the number of responses per trial). Models of behavior predicated solely on molar reinforcement contingencies all predict that runs should remain short throughout this experiment, because such runs promote both the most frequent reinforcement and the greatest reinforcement per press. To the contrary, 29 of 30 subjects emitted runs in the vicinity of the target, driving down reinforcement rate while greatly increasing the number of presses per pellet. These results illustrate the powerful effects of local reinforcement contingencies in changing behavior, and in doing so underscore a need for more dynamic quantitative formulations of operant behavior to supplement or supplant the currently prevalent static ones.     

An investigation of peak shift and behavioral contrast for autoshaped and operant behavior.

Instrumental treadle press and nonreinforced key peck responses were monitored during discrimination training and generalization testing in pigeons on positive and negative reinforcement schedules. In Experiment 1, six pigeons pressed a treadle for food on a multiple variable-interval extinction schedule. In Experiment 2, three pigeons pressed a treadle to avoid shock on a multiple free-operant avoidance extinction schedule. Different color keylights signaled S+ and S- components. Some positive behavioral contrast occurred during discrimination training, but the effect was small. Pecking occurred to the S+ keylight in Experiment 1 but not in Experiment 2. On stimulus generalization tests, all subjects displayed a positive peak shift when pressing the treadle for food or to avoid shock. However, peak shift was not found for nonreinforced "autopecks" on the stimulus key, although an area shift was observed in Experiment 1. This is the first demonstration of peak shift for pigeons pressing treadles and the only reliable demonstration of peak shift when negative reinforcement maintained responding. These results, in combination with previous demonstrations of peak shift for rats pressing levers and pigeons pecking keys, indicate that peak shift is a general by-product of operant discrimination learning, since it occurs across a variety of the organisms, responses, and reinforcers.