Successive interresponse times in fixed-ratio and second-order fixed-ratio performance

Three rats were trained on a schedule in which every sixth response produced a timeout of 5 sec minimum duration, and food was delivered at the onset of timeout. Successive interresponse times were measured under these conditions, and also when behavior was maintained by second-order fixed-ratio and fixed-interval schedules. Under the second-order schedules, each six-response fixed-ratio component was followed by a timeout, and occasionally food was delivered at the onset of a timeout. In the fixed-ratio schedule, the successive interresponse times showed a decrease followed by an increase before food delivery, but this systematic variation in interresponse times was not found when the performance was under second-order reinforcement. Under both second-order schedules the latencies of successive components, and the successive interresponse times within each component, showed a decrease as food delivery was approached.     

Limitations on environmental control of multiple fixed-ratio behavior

Eight white rats were trained to make fixed numbers of responses on each of two bars alternately in the presence of different exteroceptive stimuli. Three types of error were observed: alternating-bar switching before response requirements for reinforcement were met; perseverating-responding on the wrong bar after reinforcement; and overshooting-responding on a bar after reinforcement became available. Alternating and perseverating errors occurred mainly on the bar requiring the smaller ratio. When the ratios on the bars were changed, alternating errors were most common, but they diminished rapidly. Perseverating and overshooting errors did not diminish.     

Mand compliance as a contingency controlling problem behavior: A systematic review

Bowman et al. (1997) described a dynamic contingency in which severe problem behavior was evoked by adult noncompliance with a variety of child mands, which occurred at high rates, and was reinforced by adult compliance with subsequent mands. They discovered this phenomenon with 2 children for whom standard functional analyses were inconclusive. In recent years, similar contingencies have been shown to influence problem behavior, but the manner in which they have been arranged and described has varied across studies. The purpose of this literature review is to (a) describe contingencies involving mand compliance and the circumstances under which they have been evaluated, (b) summarize procedural variations in analysis and treatment, and (c) discuss what is known and yet to be discovered about the contingency as it relates to problem behavior. Future research focused on improving technology for analyzing and treating problem behavior suspected to be sensitive to mand compliance is discussed.     

Analysis of fixed-ratio behavior maintained by drug reinforcers.

Behavior maintained by intravenously delivered alfentanil, cocaine, or ketamine was assessed using a fixed-ratio schedule of reinforcement. As the dose of each drug was increased, rate of responding also increased up to a maximum. Further increases in dose resulted in decreased response rates (inverted U-shaped curve). An analysis of postreinforcement-pause-time and run-time measures for the ascending limb of the inverted U-shaped functions revealed that behavior was characterized by systematic decreases in both pause time and run time as dose and rate increased. An examination of the descending limb of the dose-response functions revealed that lowered response rates for cocaine and ketamine were correlated with increases in run time and small and inconsistent effects on postreinforcement pause time. Behavior maintained by rate-reducing doses of alfentanil was characterized by lengthened postreinforcement pauses with small increases in run time. These data suggest that at larger doses, drug reinforcers may have unconditioned or direct effects on the behavior that the drug is maintaining, and more important, that the nature of these unconditioned effects depends on the drug that is maintaining behavior.     

Nest material and food as reinforcers for fixed-ratio responding in mice

Three experiments investigated the importance of operant-reinforcer distance as a factor affecting continuous reinforcement (CRF) and fixed-ratio (FR) performance in mice, with nest material and food as reinforcers. In Experiment 1, nest material (paper strips) was presented on a series of FR schedules of increasing size, with the operandum located as close as possible to the reinforcer dispenser. Subjects compensated for increases in FR size by proportionately increasing their response output, but ratio strain occurred at low FR values. In Experiment 2, response rate was found to be inversely related to operant-reinforcer distance on a CRF schedule with nest material as reinforcer. In Experiment 3, food was presented on a series of FR schedules at two levels of deprivation, and with three operant-reinforcer distances. Operant-reinforcer distance was found to affect CRF response rate, degree of compensation for increases in FR size, and occurrence of ratio strain, but only when deprivation level was low. The results support the view that nest material and food share fundamentally similar reinforcing properties, but that nest material is a weaker reinforcer under normal test conditions.     

Changeover behavior under pairs of fixed-ratio and variable-ratio schedules of reinforcement

Three pigeons were studied under a pair of equal fixed-ratio schedules and a pair of equal variable-ratio schedules. Each pair was arranged as independent, concurrent schedules and also in a non-independent relation where each peck in a schedule counted toward the response requirement of both schedules. The non-independent pair of variable-ratio schedules maintained much higher changeover rates than any of the other three arrangements. Thus, two factors seemed necessary for generating high changeover rates. Responding on a schedule had to count toward the response requirement of both schedules, and the component schedules had to be variable. These data are consistent with the hypothesis that changeovers are at least partly controlled by the probability of reinforcement following a changeover.     

Schedule-induced aggression as a function of fixed-ratio value

Pigeons responding for food on fixed-ratio reinforcement schedules attacked live target birds when the ratio value was increased, but not when the value was decreased. The frequency of attacks peaked several days after ratio value change, and then gradually decreased to an original level.     

Some factors controlling preference between fixed-ratio and variable-ratio schedules of reinforcement

A multiple schedule of food reinforcement for key-pecking was arranged which consisted of nine fixed-ratios, each of which operated in the presence of a different stimulus. Pigeons could complete a given fixed-ratio within the multiple schedule or, by pecking a second key, could switch from the fixed-ratio schedule to a variable-ratio schedule consisting of the same nine ratios. Stable switching behavior was established which did not maximize simple probability or rate of reinforcement. Instead, the subjects showed a stable preference for the variable-ratio schedule of food reinforcement. Increasing the number of responses required to switch, and removing the occasions on which reinforcement was delivered after a single response in the variable schedule, decreased the number of switches to the variable schedule. Periods of delay interposed between a completed switch and the availability of reinforcement after one response in the variable schedule also decreased switching to the variable schedule, particularly at long delay intervals.     

Authority as a contingency plan

Humean constructivists object to Kantian constructivism that by endorsing the constitutivist strategy, which grounds moral obligations in rational agency, this position discounts the impact of contingency in moral life. In response to these charges, I argue that Humeans misrepresent the challenge of contingency and fail to provide adequate resources to cope with it. In its formalist variety, Humean constructivism fails to make sense of an important category of ethical judgments, which claim universal authority. The substantive varieties of Humean constructivism recognize that some ethical judgments aspire to universality, but fail to fully justify such an aspiration. These versions of constructivism represent a setback in regard to the achievements of Kantian constructivism. In conclusion, I briefly resume the advantages of advocating a Kantian conception of rational authority as a response to contingency.