Concurrent performances: rate constancies without changeover delays

Pigeons' pecks on two keys were maintained, without changeover delays, by independent variable-interval schedules of food reinforcement. Four regularly cycling 2-min components scheduled reinforcement respectively for both keys, left key only, both keys, and right key only. Initially, reinforcement scheduled for one key alone produced more responding on that key than reinforcement scheduled concurrently for both keys. Continued sessions reduced this difference; response rate on a given key approached constancy, or invariance with respect to the performance on and schedule for the other key. When extinction replaced the reinforcement schedule on either key, responding on that key decreased more during components that scheduled reinforcement for the other key than during those that did not. This demonstration that responses on one key were not supported by reinforcers on the other key suggested that the alternation of concurrent responding and either-key-alone responding prevented concurrent superstitions from developing.     

Concurrent performances: inhibition of one response by reinforcement of another

In an analysis of interactions between concurrent performances, variable-interval reinforcement was scheduled, in various sequences, for both keys, for only one key, or for neither key of a two-key pigeon chamber. With changeover delays of 0.5 or 1.0 sec, and with each key's reinforcements discriminated on the basis of key-correlated feeder stimuli, reinforcement of pecks on one key reduced the pecking maintained by reinforcement on the other key. The decrease in pecking early after reinforcement was discontinued on one key was not substantially affected by whether pecks on the other key were reinforced, but after reinforcement was discontinued on both keys, reinstatement of reinforcement for one key sometimes produced transient increases in pecking on the other key. Correlating the availability of right-key reinforcements with a stimulus, which maintained right-key reinforcement while reducing right-key pecking to negligible levels, demonstrated that these interactions depended on concurrent reinforcement, not concurrent responding. Thus, reinforcement of a response, but not necessarily the occurrence of the response, inhibits other reinforced responses. Compared with accounts in terms of excitatory effects of extinction, often invoked in treatments of behavioral contrast, this inhibitory account has the advantage of dealing only with observed dimensions of behavior.     

Concurrent performances: rate and accuracy of free-operant oddity responding

In pigeon's oddity performances, maintained by variable-interval reinforcement of pecks on the odd key of three keys in a triangular array, accuracy and response rate varied inversely with the rate of variable-interval reinforcement scheduled concurrently for pecks on a fourth, spatially isolated key. But when variable-interval and extinction components alternated in a multiple schedule for pecks on the spatially isolated key, oddity accuracy was greater during variable-interval components than during extinction components. Oddity response rate was not affected systematically by the alternating components. Changeovers between the oddity keys and the spatially isolated key were frequent during variable-interval components; responding occurred almost exclusively on the oddity keys during extinction components. This difference in performance during the two components was eliminated by arranging stimulus-correlated variable-interval reinforcement in the multiple schedule on the spatially isolated key: a stimulus was presented in the variable-interval components only when reinforcement became available, thereby reducing responding on this key to near-zero levels in both components while maintaining the variable-interval reinforcement. The effect of the multiple-schedule components on oddity accuracy was not altered, however, and thus apparently depended directly on concurrent reinforcement and not on differential sequential properties of concurrent responding during the two components.     

Academic response rate as a function of teacher- and self-imposed contingencies

The purpose of this study was to assess the effects of the contingency manager (teacher or pupil) on a pupil's academic response rate. The results of two such experiments disclosed that higher academic rates occurred when the pupil arranged the contingency requirements than when the teacher specified them. A third study manipulated only reinforcement magnitude to ascertain whether amount of reinforcement had interacted with pupil-specified contingencies to produce the increase in academic response rate. The latter findings revealed that the contingency manager, not reinforcement magnitude, accounted for this subject's gain in performance.     

Concurrent performances: effect of punishment contingent on the switching response

Pigeons' key-pecking responses were maintained under concurrently available variable-interval schedules of reinforcement. Responses in the presence of two different key-colors were reinforced on two independent and concurrent variable-interval schedules of food reinforcement, each associated with one of the key colors (red or green). Pecks at a second key (changeover key), always white, would alternate the colors on the main key. In Exp. 1 and 2, electric shock of 50 msec duration followed immediately after changeovers. The proportion of responses in the presence of the color associated with the higher frequency of reinforcements per hour was a direct function of shock intensity contingent on changeovers. When both schedules provided equal number of reinforcements per hour, there was no systematic effect of shock intensity on response distribution. In Exp. 3, a timeout period was contingent on changeovers, and response distribution was a function of timeout length.     

Concurrent performances: a baseline for the study of conditioned anxiety

Three rats were trained to lever press on concurrent random interval 2-min random interval 2-min schedules of milk reinforcement. With a 5-sec changeover delay, relative response rate matched the relative reinforcement duration associated with each lever. A stimulus, during which unavoidable shocks occurred at random intervals, was superimposed on this concurrent baseline, and shifts in preference were found. However, data from this procedure were ambiguous, apparently confounded by shock-elicited response bursts. Termination of the shocks during the stimulus resulted in a rapid recovery of matching, which was preceded by a brief facilitation of responding on the less-preferred lever. The procedure was then changed to a conventional conditioned anxiety paradigm with a variable duration pre-shock stimulus. A marked shift in relative response rate towards the preferred lever was found in all three rats; that is, responding on the preferred lever was far less suppressed during the pre-shock stimulus than responding on the less-preferred lever.     

Concurrent performances: a baseline for the study of reinforcement magnitude

When a pigeon's pecking on a single key was reinforced by a variable-interval (VI) schedule of reinforcement, the rate of pecking was insensitive to changes in the duration of reinforcement from 3 to 6 sec. When, however, the pigeon's pecking on each of two keys was concurrently reinforced by two independent VI schedules, one for each key, the rate of pecking was directly proportional to the duration of reinforcement.     

Effects of manipulating an antecedent event on mathematics response rate

The purpose of this investigation was to assess the effects on performance rate of simply writing the answers to mathematics problems versus verbalizing the problems before making a written response. The subject was an 11-yr-old boy whose response accuracy on mathematics problems was very erratic. Three experiments were conducted, each consisting of three phases. In each first phase, the subject was requested to write the answers to sets of mathematics problems. In the second, he was required to verbalize the problem before writing the answer. In the third phase, the subject was told to write the answer again without prior verbalization. The results indicated that the subject's correct answer rate increased and his error rate decreased as a result of his verbalizing the problems before making a written response. Results further revealed that in the final phase of each experiment, the return to the original conditions, his correct answer rate continued to increase.     

Eye movements as a function of response contingencies measured by blackout technique

A program may have a low error rate but, at the same time, require little of the student and teach him little. A measure to supplement error rate in evaluating a program has recently been developed. This measure, called the blackout ratio, is the percentage of material that may be deleted without increasing the error rate. In high blackout-ratio programs, obtaining a correct answer is contingent upon only a small portion of the item. The present study determined if such low response-contingent material is read less thoroughly than programmed material that is heavily response-contingent. Eye movements were compared for two versions of the same program that differed only in the choice of the omitted words. The alteration of the required responses resulted in a version with a higher blackout ratio than the original version, which had a low blackout ratio. Eighteen undergraduates received half their material from the high and half their material from the low blackout-ratio version. The order was counterbalanced. Location and duration of all eye fixations in each item were recorded by a Mackworth Eye Marker Camera. On high blackout-ratio material, subjects used fewer fixations, shorter fixation time, and shorter scanning time. High blackout-ratio material failed to evoke the students' attention.     

Concurrent performances: reinforcement by different doses of intravenous cocaine in rhesus monkeys

Different doses of intravenous cocaine reinforced the lever pressing of rhesus monkeys under two-lever concurrent or concurrent-chain schedules. Under the concurrent procedure, responding produced drug reinforcers arranged according to independent variable-interval 1-min schedules. Under the concurrent-chain procedure, responding in the variable-interval link led to one of two mutually exclusive, equal-valued, fixed-ratio links; completion of the ratio produced a drug reinforcer. Under both procedures, responding on one lever produced a constant dose of 0.05 or 0.1 mg/kg/injection, while on the other lever, dose was systematically varied within a range of 0.013 to 0.8 mg/kg/injection. Preference, indicated by relative response frequency on the variable-dose lever during the variable-interval link, was always for the larger of the doses. Relative response frequencies on the variable-dose lever roughly matched relative drug intake (mg/kg of drug obtained on variable lever divided by mg/kg of drug obtained on both levers). For many dose comparisons, responding occurred and reinforcers were obtained almost exclusively on the preferred lever. Overall variable-interval rates generally were lower than with other reinforcers, and these low rates, under the experimental conditions, may have occasioned the exclusive preferences.     

Response slowing of older adults: effects of time-limit contingencies on single- and dual-task performances

Younger and older men (18-25 vs. 65-76 years of age) were given extended practice (44 hr) with a memory scanning procedure in which lists of visual and auditory items were presented singly (single-task condition) or together with a second visual or auditory list (dual-task condition). For both age groups, identification of test items was slower with the dual-task procedure, and experience with the tasks produced only small changes in response latencies. When time limits were placed on responding, latencies decreased substantially, and the difference between single and divided tasks was reduced. Although the older men were slower throughout the experiment, the time limit contingency reduced age differences in responses to both tasks. The task effect was larger for the older men, but this age difference also was reduced by the time limit procedures.     

Combined-stimulus control as a function of the response rate controlled by the absence of the single stimuli

Rat's bar-press responses were maintained at moderate rates during separate presentations of light and tone by separate but concurrent variable-interval schedules of food and shock presentation. The relative response rate maintained during light-out-no-tone was alternated in four successive phases: in Phases 1 and 3 responding was maintained at a higher rate than that during light and tone alone by a variable-interval food schedule, while in Phases 2 and 4 responding was reduced to a lower rate by a differential-reinforcement-of-other-behavior food schedule. In test presentations of light, tone and a light-plus-tone combination, administered at the end of each phase, the proportion of responses emitted during light-plus-tone was an inverse function of the relative response rate controlled by light-out-no-tone, indicating that the relative training response rate controlled by the absence of the single stimuli determined the control exerted by the combined stimuli. Different relative response rates maintained in training may also be partly responsible for previously observed differences in the form of generalization gradients following the establishment of multi-stimulus control.     

Concurrent performances: stimulus-control gradients during schedules of signalled and unsignalled concurrent reinforcement

On one key, pigeons' pecks were reinforced according to a variable-interval schedule in the presence of vertical lines, and were not reinforced in the presence of oblique lines. On a second key, pecks were reinforced according to a variable-interval schedule in the presence of blue, according to a signalled variable-interval schedule in the presence of red, and were not reinforced in the presence of white. Subsequently, during extinction, stimulus-control gradients were obtained by presenting eight different line orientations on the first key concurrent with each of the three colors on the second key. On the first key, line-orientation gradients tended to be lower, narrower, and less shifted in peak or area when the second-key stimulus was blue or red, the stimuli respectively correlated with unsignalled and signalled reinforcement, than when it was white, the stimulus correlated with extinction. Thus, the effect on first-key line-orientation gradients depended on second-key stimuli correlated with concurrent reinforcement, whether or not these stimuli were also correlated with concurrent responding. As a function of first-key line orientation, an inverted gradient was obtained on the second key during blue; during both red and white, rates of pecking on the second key were near zero.     

Precurrent contingencies: Behavior reinforced by altering reinforcement probability for other behavior

The present study explored the effects of a precurrent contingency in which one (precurrent) activity increased the reinforcement probability for another (current) activity. Four human subjects responded on a two-key computer mouse. Each right-key press was reinforced (points exchangeable for money) with .02 probability. In one condition (no precurrent contingency), pressing the left key had no scheduled consequence; in another condition (precurrent contingency), pressing the left key increased the reinforcement probability for right-key responding to .08 for 15 s. Initial exposure to the precurrent contingency resulted in acquisition of precurrent left-key responding for 3 subjects, but for the 4th subject a special contingency was required. Right-key responding occurred at a high stable rate across the conditions. Changeovers to left-key responding dropped to near zero when the precurrent contingency was absent and were maintained at enhanced levels when the precurrent contingency was present. Contacts with the left key consisted of short response runs. Right-key responses were more frequently emitted within 15 s of a left-key response when the precurrent contingency was present, an efficient adaptation to the contingency. Continued research on precurrent behavior may produce insights into complex phenomena such as autoclitics and self-control.     

A sequent calculus for a logic of contingencies

We introduce a sequent calculus that is sound and complete with respect to propositional contingencies, i.e., formulas which are neither provable nor refutable. Like many other sequent and natural deduction proof systems, this calculus possesses cut elimination and the subformula property and has a simple proof search mechanism.     

Concurrent schedules: Spatial separation of response alternatives

Four pigeons were exposed to independent concurrent variable-interval 20-second variable-interval 60-second schedules of reinforcement. A transparent partition was inserted midway between the two response keys. The length of the partition was systematically manipulated. Increasing partition length produced a decrease in changeover rate in Experiment 1. Over-matching was observed with a partition length of 20 centimeters. In Experiment 2 a four-second limited hold was added to the schedules. Increasing partition length produced a decrease in changeover rate that exceeded the decrease observed in Experiment 1. This manipulation produced nearly exclusive choice of the variable-interval 20-second component. The present results, together with results obtained in related research, suggest that deviation from matching is a function of procedural variables that determine the consequences of a changeover response.     

Group contingencies for group consequences in classroom management: a further analysis

The relative effects of rules, rules + feedback, and rules + feedback + group and individual consequences for appropriate behavior were investigated in three elementary classrooms during reading and mathematics periods. The consequences were individual and group praise, and group activities. The total intervention package (rules + feedback + group and individual consequences) was most effective in increasing appropriate behavior. Rules + feedback produced increased appropriate behavior in two of the three classrooms. Rules alone produced no change in classroom behavior. Maintenance of appropriate classroom behavior was noted approximately three weeks after the program ended. Teacher's correct use of praise was also maintained for two of the three teachers at levels generated during the total package condition.     

Reinforcer effectiveness as a function of reinforcer rate and magnitude: a comparison of concurrent performances

Pigeons' pecks on each of two concurrently available response keys were reinforced under a variable-interval schedule that sometimes allotted food-pellet deliveries to one key and sometimes to the other. The keys differed in the number of reinforcements assigned to each and in the number of pellets delivered during each reinforcement. When the total quantity of food associated with each key during a session was constant, the proportion of responses to a key depended on the particular combinations of reinforcer rate and reinforcer magnitude scheduled on each key. A given quantity of food generated more responding on a key when it was delivered frequently in small amounts than when it was delivered infrequently in large amounts.