bluuebunny/crossref_metadata_2025 huggingface dataset:
LATENCY AND FREQUENCY OF RESPONDING UNDER DISCRETE‐TRIAL FIXED‐INTERVAL SCHEDULES OF REINFORCEMENT1
Authors: Hienz Robert D. , Eckerman David A.
Published: March 2006

Pigeons' key pecking was studied under a number of discrete‐trial fixed‐interval schedules of food reinforcement. Discrete trials were presented by briefly illuminating the keylight repetitively throughout the interreinforcement interval. A response latency counterpart to the fixed‐interval scallop was found, latency showing a gradual, negatively accelerated decrease across the interval. This latency pattern was largely invariant across changes in fixed‐interval length, number of trials per interval, and maximum trial duration. Frequency of responding during early trials in the intervals varied, however, with different schedule parameters, being directly related to fixed‐interval length, inversely related to number of trials, and complexly affected by conjoint variations of fixed‐interval length and number of trials. Response latency thus was found to be simply related to elapsed time during the interval while response frequency was complexly determined by other factors as well.
EFFECTS OF REINFORCEMENT RATE AND REINFORCER MAGNITUDE ON CHOICE BEHAVIOR OF HUMANS1
Authors: Schmitt David R.
Published: March 2006

Two experiments with human subjects investigated the effects of rate of reinforcement and reinforcer magnitude upon choice. In Experiment 1, each of five subjects responded on four concurrent variable‐interval schedules. In contrast to previous studies using non‐human organisms, relative response rate did not closely match relative rate of reinforcement. Discrepancies ranged from 0.03 to 0.43 (mean equal to 0.19). Similar discrepancies were found between relative amount of time spent responding on each schedule and the corresponding relative rates of reinforcement. In Experiment 2, in which reinforcer magnitude was varied for each of five subjects, similar discrepancies ranging from 0.05 to 0.50 (mean equal to 0.21), were found between relative response rate and relative proportion of reinforcers received. In both experiments, changeover rates were lower on the long‐interval concurrent schedules than on the short‐interval ones. The results suggest that simple application of previous generalizations regarding the effects of reinforcement rate and reinforcer magnitude on choice for variable‐interval schedules does not accurately describe human behavior in a simple laboratory situation.
HIGH‐ORDER CONCEPT FORMATION IN THE PIGEON1
Authors: Lubow Robert E.
Published: March 2006

After 30 days of operant training, with pecking responses to aerial photographs containing man‐made objects reinforced with food, and no food reinforcement for pecking on photographs not containing man‐made objects, a discrimination to the two classes of photographs was obtained. The discriminative response generalized to photographs with which the pigeons had no previous experience. This study demonstrates that pigeons are capable of forming relatively high‐order concepts. Some possible stimulus properties controlling the discrimination are discussed.
PREFERENCE FOR AND EFFECTS OF VARIABLE‐AS OPPOSED TO FIXED‐REINFORCER DURATION1
Authors: Essock Susan M. , Reese Ellen P.
Published: March 2006

Pigeons were trained on multiple schedules in which a fixed number of pecks produced either a fixed or a variable period of access to food, the average variable‐duration reinforcement equalling the fixed. Pecking rates were generally higher during the variable‐duration component. Subsequent performance on concurrent schedules revealed an initial preference for variable‐duration reinforcement for all subjects; for most subjects, this preference was sustained. For one subject, the average variable duration was gradually reduced to half the fixed duration: continued preference for the variable component resulted in a loss of up to 30% of available reinforcement time. A return to multiple schedules with unequal pay‐off shifted the preference to the greater fixed duration, and this preference was maintained even when the variable duration was again raised to equal the fixed duration. For the remaining subjects, the initial variable‐duration preference on concurrent schedules was gradually replaced by a side preference. When the range of variable durations was varied, keeping the average variable duration equal to the fixed, the occasional longer reinforcers sustained a preference for variable‐reinforcer durations for three of the four subjects.
TIME‐ALLOCATION, MATCHING, AND CONTRAST1
Authors: Shimp Charles P. , Hawkes Larry
Published: March 2006

A variable‐interval schedule arranged food reinforcement for key pecking by pigeons on a single operandum at two rates, corresponding to two classes of reinforced interresponse times ranging from 1.5 to 2.5 sec and from 3.5 to 4.5 sec. The scheduled reinforcement rate for the higher component response rate was constant and equivalent to that of a variable‐interval 4‐min schedule. The scheduled reinforcement rate for the lower component response rate varied from zero to over 100 per hour. The number of occurrences of the constant component response rate varied inversely with the reinforcement rate for the variable component. This result, by definition a concurrent reinforcement interaction, or contrast, was the combined effect of two time‐allocation functions, which together determine mean response rate: the time allocated to both component rates as a function of the total reinforcement rate, and the time allocated to a particular component rate as a function of the percentage of reinforcements for that component. The present experiment reveals a further parallel between the controlling relations for free responding on a single operandum and those for choice between two operanda; in each case, a concurrent reinforcement interaction can be found that corresponds to matching.
RESPONSE‐PRODUCED TIMEOUTS UNDER A PROGRESSIVE‐RATIO SCHEDULE WITH A PUNISHED RESET OPTION
Authors: Dardano J. F.
Published: March 2006

Three behavioral options were available to food‐deprived pigeons: (1) pecking one key resulted in food reinforcement according to a 50‐response progressive‐ratio schedule, (2) pecking a second key reset the progressive‐ratio schedule to the initial progressive‐ratio step, and (3) pecking a third key produced a 3‐min timeout period. Pecks on the reset key were shocked. Under low and intermediate shock intensities, timeouts were not produced; Final Acceptance under high shock levels, timeouts were produced regularly. Timeouts occurred during the initial period of a progressive‐ratio step and were more frequent during the longer steps of the progressive‐ratio schedule. Response‐produced timeouts under these experimental conditions could be interpreted either as an escape from aversive behavioral options or as a low‐probability behavior emerging when the food reinforcement schedule exerted weaker control.
PREFERENCE FOR FIXED‐INTERVAL TERMINAL LINKS IN A THREE‐KEY CONCURRENT CHAIN SCHEDULE
Authors: Davison M. C. , Temple W.
Published: March 2006

Pigeons were trained on three‐key concurrent chain schedules in which the initial links were variable‐interval schedules and the terminal links were fixed‐interval schedules. In the first experiment, the initial links were all equal and the terminal‐link schedule on one key only was varied. In the second part of the experiment, the terminal‐link schedules were all fixed, but different, and the initial‐link schedule on one key was varied. Relative response rates in the initial links did not match either the relative arranged, nor the relative obtained, terminal‐link reinforcement rates. The relations between independent and dependent variables in three‐key concurrent chains were similar to, but not identical with, those found in two‐key chains comprising the same schedule types.
GROUP BEHAVIOR OF RATS UNDER SCHEDULES OF REINFORCEMENT1
Authors: Grott Robert , Neuringer Allen
Published: March 2006

Groups of three rats were placed in a chamber containing one response lever and one water dispenser. A variety of schedule conditions were explored including fixed ratio, extinction, satiation, fixed interval, fixed time, differential reinforcement of low rates, and discrimination learning. Each group was treated as a single unit, with the collective lever responses emitted by the three rats being the main dependent variable. Group responding was found to be controlled by the reinforcement schedules in an orderly and consistent manner. However, the groups often paused less and responded faster than individual rats working under identical conditions.
MOTIVATION IN CONCURRENT VARIABLE‐INTERVAL SCHEDULES WITH FOOD AND WATER REINFORCERS1
Authors: Willis Richard D. , Van Hartesveldt Carol , Loken Kristen K. , Hall Deborah C.
Published: March 2006

The lever pressing of four food‐ and water‐deprived rats was reinforced on concurrent variable‐interval schedules. Food reinforced one response, and water reinforced the other. Response rates in baseline were higher in the food component than in the water component. After response patterns and body weights had stabilized, the animals were given access to either food only, water only, both food and water, or neither food nor water (baseline) before daily sessions. Giving food before a session decreased per cent time in the food component, decreased overall response rates for food, and increased overall response rates for water. Giving water before a session increased per cent time in the food component, increased overall response rates for food, and decreased overall response rates for water. Giving both food and water before a session resulted in a combination of prefeeding and prewatering effects. More food and more water were consumed when both were available than when only one was available before a session.
CENTRIFUGAL SELECTION OF SIGNAL‐DIRECTED PECKING1
Authors: Barrera F. J.
Published: March 2006

Pigeons were exposed to a schedule of stimulus‐correlated food presentations. When key pecks terminated trial signals and cancelled the delivery of food, pecking was either gradually or rapidly redirected away from the keys, depending on whether the food‐omission contingency was introduced from the outset or after exposure to a response‐independent baseline. In all cases, the food‐omission contingency substantially reduced or eliminated pecking at the keys.
COMBINATIONS OF RESPONSE‐REINFORCER DEPENDENCE AND INDEPENDENCE1
Authors: Lattal Kennon A.
Published: March 2006

The contribution of the response‐reinforcer dependency to the control of behavior was investigated. Pigeons were trained to key peck under a variable‐interval schedule of reinforcement. With the total number and temporal distribution of reinforcer deliveries in experimental sessions constant, the effects of varying the percentage of response‐independent reinforcement were examined. At different times, 100%, 66%, 33%, 10%, or 0% of the scheduled reinforcers were delivered dependent upon key pecking and the remainder were delivered independently of responding. Response rates were related to the percentage of response‐dependent reinforcement with lower response rates associated with smaller percentages of response‐dependent reinforcement. The results suggest that the response‐reinforcer relation exerts control over behavior in a manner similar to that exerted by other parameters of reinforcement.
SOME FACTORS INVOLVED IN THE COMPARISON OF RESPONSE SYSTEMS: ACQUISITION, EXTINCTION, AND TRANSFER OF HEAD‐POKE AND LEVER‐PRESS SIDMAN AVOIDANCE1
Authors: Ayres John J. B. , Benedict James O. , Glackenmeyer Richard , Matthews William
Published: March 2006

Head poking, a suggested natural escape reaction to shock for the rat, was compared to lever pressing in a Sidman avoidance study. Both responses could be emitted at any time, but only one was effective in a given session. Acquisition and extinction of the two responses were compared under both signalled and unsignalled avoidance. Then, a test for transfer was conducted in which acquisition conditions were re‐instated, but the effectiveness of the responses was reversed. Three differences between responses were noted: (a) head poking was superior in reducing shock rates under signalled conditions; (b) head poking was more resistant to extinction, especially under signalled conditions; (c) under unsignalled conditions, animals were unable to learn to head poke if they had previously learned to lever press. Findings a and c were pursued in later experiments. Finding a depended on the location of the warning signal with respect to the response system. When the lever press required approach to the warning signal, the head poke was superior. But when the head poke required approach to the warning signal, the two responses were equally effective. Finding c depended on the absence of feedback for head poke during transfer. Two conclusions are offered: first, the two responses appear to obey the same laws when their topographical differences are taken into account. Second, response feedback appears to be more critical in transfer than in original acquisition.
THE DISRUPTION OF AUTOSHAPED KEY PECKING IN THE PIGEON BY FOOD‐TRAY ILLUMINATION1
Authors: Wasserman Edward A. , Mccracken Scott B.
Published: March 2006

Two experiments investigated the effect of food‐tray illumination on pecking a lighted key that signalled food presentation. Pigeons key pecked less when both feeder and key stimuli preceded grain delivery than when the keylight alone signalled food. This detractive influence of grain‐tray illumination did not result after prior pairings of the keylight with food. The involvement of associative and physical variables in autoshaping the pigeon's key peck is considered in light of these findings.
RELATIVE AND ABSOLUTE DENSITY OF REINFORCEMENT AS FACTORS INFLUENCING THE PEAK SHIFT1
Authors: Wheatley Kimbal L. , Thomas David R.
Published: March 2006

Four groups of six pigeons each were given nondifferential training on multiple variable‐interval variable‐interval reinforcement schedules and then were switched to differential training involving a multiple schedule in which reinforcement density was reduced in one of the two components. The multiple schedules used in the four groups had mean interreinforcement intervals of 1 min and 1 min in the two components changed to 1 min, 5 min; 2.5 min, 2.5 min changed to 2.5 min, 5 min; 12 sec, 12 sec changed to 12 sec, 24 sec; and 12 sec, 12 sec changed to 12 sec, 60 sec. In subsequently administered wavelength generalization tests, some peak shifts were observed in each condition and occurred occasionally in the absence of behavioral contrast or rate reduction in the less‐reinforced component. The best predictor of peak shift was a high proportion of total responses emitted during the more‐reinforced component at the end of differential training.
BEHAVIORAL CONTRAST WITH MULTIPLE POSITIVE AND NEGATIVE STIMULI ON A CONTINUUM1
Authors: Farthing G. William
Published: March 2006

After an initial period of nondifferential training, six pigeons were trained on a go/no‐go discrimination involving 12 line tilts from vertical clockwise to horizontal. Responses to the first six tilts (positive stimuli) were reinforced on a variable‐interval one‐minute schedule, whereas responses to the other six tilts (negative stimuli) were extinguished. During the first several discrimination sessions, the highest response rate was typically to one of the positive stimuli that was relatively close to the negative stimuli or at an intermediate distance, rather than to one of the positive stimuli most distant from the negative stimuli. This effect decreased with extended training up to 50 or 80 sessions.
RESPONSE RATE, REINFORCEMENT FREQUENCY, AND BEHAVIORAL CONTRAST
Authors: Thomas G. V. , Cameron G. N.
Published: March 2006

Pigeons responded for food on a multiple schedule in which periods of green‐key illumination alternated with periods of red‐key illumination. When behavior had stabilized with a variable‐interval 2‐min schedule of reinforcement operating during both stimuli, low rates of responding (interresponse times greater than 2 sec) were differentially reinforced during the green component. Conditions during the red stimulus were unchanged. Response rates during the green component fell without changing the frequency of reinforcement but there were no unequivocal contrast effects during the red stimulus. The frequency of reinforcement during the green component was then reduced by changing to a variable‐interval 8‐min schedule without reducing the response rates in that component, which were held at a low level by the spacing requirement. Again, the conditions during the red stimulus were unchanged but response rates during that stimulus increased. These results show that reductions in reinforcement frequency, independently of response rate, can produce interactions in multiple schedules.
BEHAVIORAL CONTRAST WITHOUT RESPONSE‐RATE REDUCTION1
Authors: Halliday M. S. , Boakes R. A.
Published: March 2006

Behavioral contrast was obtained in two experiments, which both employed a standard free‐operant successive discrimination (a multiple variable‐interval extinction schedule), without the occurrence of reductions of response rate in the extinction component. In Experiment I, one group of four pigeons was trained on a multiple schedule in which one stimulus was associated with a variable‐interval schedule and the second stimulus with response‐independent reinforcement on a free variable‐interval schedule. Though by the end of this training three pigeons were responding very little to the second stimulus, when this stimulus was associated with extinction all subjects showed a contrast effect. In Experiment II, eight pigeons were trained extensively to respond to a single stimulus on a variable‐interval schedule, before a second stimulus associated with extinction was introduced. This second stimulus was dissimilar to the initial stimulus and five pigeons never responded in its presence. Nevertheless, all pigeons showed a contrast effect and there was no evidence that the effect was smaller in errorless subjects or smaller than in a subsequent discrimination where all subjects made many errors. Both experiments indicated that response reduction in one component of a multiple schedule is not a necessary condition for the occurrence of contrast.
PEAK SHIFT AS A FUNCTION OF MULTIPLE SCHEDULES OF REINFORCEMENT1
Authors: Dysart Judy , Marx Melvin H. , McLean Jim , Nelson James A.
Published: March 2006

Pigeons were trained to respond to two stimuli on the wavelength continuum, 550 nm and 570 nm, each correlated with an independent schedule of reinforcement. The multiple schedule component in effect during 550 nm (SI) was always a variable‐interval 1‐min. During the 570‐nm stimulus (S2) the second component of the schedule was either variable‐interval 30‐sec, 1‐min, 2‐min, 5‐min, or extinction for different groups of birds. Generalization gradients were obtained after this training, with the following results: (1) response rate to SI during training was related to the reinforcement frequency associated with S2; the distribution of responding during generalization testing was a function of the schedules of reinforcement used during training and the response rates they produced. Decreases in the relative frequency of reinforcement correlated with S2 resulted in increases in the distribution shift of responses away from S2 during generalization testing.
CONTEXT, OBSERVING BEHAVIOR, AND CONDITIONED REINFORCEMENT1
Authors: Auge Robert J.
Published: March 2006

Pigeons made observing responses for stimuli signalling either a fixed‐interval 30‐sec schedule or a fixed‐ratio x schedule, where x was either 20, 30, 100, 140, or 200 and the schedules alternated at random after reinforcement. If observing responses did not occur, food‐producing responses occurred to a stimulus common to both reinforcement schedules. When the fixed‐interval schedule was paired with a low‐value fixed ratio, i.e., 20 or 30, the presentation of the stimulus reliably signalling the fixed‐ratio schedule reinforced observing behavior, but the presentation of the stimulus reliably signalling the fixed‐interval schedule did not. The converse was the case when the fixed‐interval schedule was paired with a large‐valued fixed ratio, i.e., 100, 140, or 200. The results demonstrated that the occasional presentation of the stimulus signalling the shorter interreinforcement interval was necessary for the maintenance of observing behavior. The reinforcement relationship was a function of the schedule context and was reversed by changing the context. Taken together, the results show that the establishment and measurement of conditioned reinforcement is dependent upon the context or environment in which stimuli reliably correlated with differential events occur.
EFFECTS OF THE DIFFERENCE BETWEEN SELF AND COACTOR SCORES UPON THE AUDIT RESPONSES THAT ALLOW ACCESS TO THESE SCORES1
Authors: Vukelich Ron , Hake Don F.
Published: March 2006

An audit response allows access to an existing score from a subject's own performance (self audit) or from his coactor's performance (coactor audit). A previous study found that social stimuli (coactor present) increased audits relative to a non‐social (no coactor) condition. The increase, designated a social‐stimulus effect, was found to be due more to the coactor's score than to his mere presence. This finding suggested that the difference between self and coactor scores might affect the size of the social‐stimulus effect. In the present study, six pairs of human subjects matched‐to‐sample for points that were exchangeable for money. During a session, matching‐to‐sample problems were distributed so that a subject's score was ahead, behind, or about even with his coactor's score. The even condition produced the largest social‐stimulus effects, i.e., the most audits that could not be attributed to nonsocial variables such as time or number of problems. The even condition may have produced the largest social‐stimulus effects because it was the only condition where the major social reinforcer (being ahead) could be both present or absent and, consequently, the even condition was the only one where audits had a discriminative function with respect to the presence of the major social reinforcer.
CHAINED CONCURRENT SCHEDULES: REINFORCEMENT AS SITUATION TRANSITION1
Authors: Baum William M.
Published: March 2006

Pigeons' pecks at two white response keys (initial‐link situation) occasionally turned both keys red (terminal‐link situation). When the two keys were red, pecks occasionally produced food, after which the keys were again white. In both situations, a changeover delay prevented the response‐produced outcome from immediately following a change of responding from either key to the other. In the initial‐link situation, the ratio of pecks at the keys closely paralleled the ratio of transitions into the terminal‐link situation produced by the pecks, conforming to the well‐known matching relation. In the terminal‐link situation, the peck ratios deviated from the matching relation toward indifference. Overall response rate and rate of changeover were generally higher in the terminal‐link situation than in the initial‐link situation. The finding of matching in the initial‐link situation supports a definition of reinforcement as situation transition. The differences in performance between the two situations, viewed in the light of other recent findings, suggest that the effects of a changeover delay depend on the overall reinforcing value of the choice alternatives.
FREQUENCY OF REINFORCEMENT AS A DETERMINANT OF EXTINCTION‐INDUCED AGGRESSION DURING ERRORLESS DISCRIMINATION LEARNING1
Authors: Rilling Mark , Caplan Harry J.
Published: March 2006

Seven pigeons were trained to discriminate without errors between a green keylight and a dark key. The key‐pecking response was reinforced in the presence of green, and extinction was in effect in the presence of the dark key. The opportunity to attack a restrained target pigeon was present only during extinction. Both variable‐interval 30‐sec and fixed‐ratio 1 schedules of reinforcement during the positive stimulus induced a higher rate of attack during extinction than a variable‐interval 5‐min schedule. The highest rate of attack during extinction occurred during the first 20 sec after the positive stimulus terminated. Hence, the withdrawal of the positive condition, rather than the consequences of the pecking response during extinction, appears to be one of the primary factors responsible for attack between pigeons during extinction. Behavioral contrast, denned as a decrease in the rate of responding when the positive stimulus was presented alone, was obtained from the four birds that displayed the lowest overall rates of attack, while the three birds with the highest attack rates did not display behavioral contrast. For the birds without contrast, components of the attack response during the positive stimulus presumably competed with and reduced the rate of pecking the key, thereby precluding behavioral contrast.
THE CONTROL OF SWITCHING INTO BLACKOUT DURING EXTINCTION1
Authors: von Sturmer G. , Beale I. L. , Davison M. C.
Published: March 2006

During the extinction component of a multiple variable‐interval extinction schedule, four pigeons learned to peck a second key that switched off the keylights. Two experiments attempted to isolate the events that control this behavior. In the first experiment, switching into blackout was equally maintained when switches were restricted to the first minute as when they were restricted to the last minute of the extinction component. When switches could be emitted in the first and last minutes, they occurred more frequently in the first. Restricting switching to the first minute of each component and eliminating the blackout between components had no effect on switching. In the second experiment, when the stimulus correlated with extinction was omitted, switching decreased slightly. Omission of both multiple schedule stimuli decreased the switching rate, but switching was still maintained. Food reinforcement was then omitted and switching by two birds increased. Switching ceased when blackout was no longer the consequence of pecking the switching key. It was concluded that switching was not controlled by the similarity of the blackouts produced by the switching key and those that occurred between components; nor was it maintained by the temporal proximity of switching responses to the onset of the reinforced component. Finally, switching did not appear to be controlled by the main‐key stimuli correlated with the components of the multiple schedule.
PSYCHOLINGUISTICS DISCOVERS THE OPERANT: A REVIEW OF ROGER BROWN'S A FIRST LANGUAGE: THE EARLY STAGES1
Authors: Segal Evalyn F.
Published: March 2006

Brown's book is selectively reviewed with the aim of noting points of similarity between Brown's psycholinguistic analysis of language acquisition and a functional analysis of verbal behavior. Brown divides early language acquisition into five stages, based on mean length of utterance in samples of child speech. His book concentrates on Stage I, when mean length of utterance first rises above 1.0, indicating that children are beginning to speak in multi‐morphemic utterances, and Stage II, when mean length of utterance in morphemes is about 2.25. Multi‐morphemic utterances in Stage I consist mainly of ordered sequences of uninflected nouns and verbs, the order being that of the simple declarative sentence (agent‐action‐indirect object‐direct object‐locative). The review attempts a theoretical analysis of the functional stimulus control of Stage I syntactic order, concluding that the control must originate partly in relations among events in the environment and partly in covert autoclitic verbal behavior. Increases in mean length of utterance in Stage II are mainly due to the appearance of several “grammatical morphemes” such as the progressive ‐ing inflection on verbs and the plural ‐s inflection on nouns. The review attempts a behavioral paraphrase, again in terms of tacts and autoclitics, of Brown's psycholinguistic analysis of grammatical morphemes, concluding that Stage II displays the further development, building on Stage I, of the combined control of verbal behavior by relations in the environment and covert self‐generated verbal stimuli. Similarities between Brown's psycholinguistic analysis and a functional analysis of language acquisition suggest that the two viewpoints are converging on a common concern with the stimulus control of verbal behavior.
DISCRIMINATIVE STIMULUS LOCATION AS A DETERMINANT OF POSITIVE AND NEGATIVE BEHAVIORAL CONTRAST IN THE PIGEON1
Authors: Schwartz Barry
Published: March 2006

Four pigeons were exposed to a series of two‐component multiple schedules of reinforcement that ordinarily yield positive and negative behavioral contrast. The stimuli that signalled the component schedules were sometimes located on the response key and sometimes off. Positive behavioral contrast was observed only when the stimuli were on the key. Negative contrast was observed independent of stimulus location. These data suggest that positive and negative contrast may be causally unrelated, and support an account of contrast in terms of the summation of key pecks that are separately controlled by response‐reinforcer and stimulus‐reinforcer dependencies.
RESPONSE ADDITIVITY: EFFECTS OF SUPERIMPOSED FREE REINFORCEMENT ON A VARIABLE‐INTERVAL BASELINE1
Authors: Boakes R. A. , Halliday M. S. , Poli M.
Published: March 2006

Three experiments examined the effects of superimposing free reinforcement (Free VI 30‐sec) on behavior maintained by a response dependent mult VI 2‐min VI 2‐min schedule of reinforcement. Experiment I used pigeons as subjects, key pecking as the response, and colors of response key as the stimuli associated with the multiple‐schedule components. When free reinforcement was added during only one component (Differential condition) a large and highly significant increase in response rate developed in this component. Adding free reinforcement during both components (Nondifferential condition) produced smaller and far less‐consistent effects. An entirely different pattern of results was obtained in two subsequent experiments, where similar procedures and reinforcement conditions were used with rats as subjects and bar pressing as the response. In both Experiments II and III, response rates decreased to the stimulus associated with added free reinforcement in the Differential condition. These findings are interpreted as the result of interactions between behavior maintained by response‐reinforcer contingencies and behavior maintained by stimulus‐reinforcer contingencies. As such, they support the main assumption of an auto‐shaping theory of behavioral contrast, that additivity of responding generated by the two kinds of contingency can occur only in situations favorable to autoshaping.
GENERALIZATION OF EXCITATION AND INHIBITION AFTER DIFFERENT AMOUNTS OF TRAINING OF AN AVOIDANCE BASELINE1
Authors: Rilling Mark , Budnik John E.
Published: March 2006

After acquisition of a treadle‐pressing response maintained by an avoidance contingency, four groups of pigeons received interdimensional discrimination training. For two groups, the positive stimulus was a 1000‐Hertz tone correlated with the avoidance schedule and the negative stimulus was noise correlated with extinction. The discriminative stimuli were reversed for the other two groups. For two groups, the test stimuli were presented during extinction without any shocks during the test stimuli, for the other two groups, an unavoidable shock was presented during each test stimulus. Generalization was measured daily during discrimination training by randomly substituting each of six test frequencies for the 1000‐Hertz tone. When the 1000‐Hertz tone was correlated with the avoidance schedule, the number of responses to it increased and the excitatory gradient became steeper as a function of the amount of training. When the 1000‐Hertz tone was associated with extinction, the number of responses to it decreased as a function of days of training and the inhibitory gradient became slightly steeper, provided that responding to the test stimulus was elevated by unavoidable shock. The training effects parallel those obtained with positive reinforcement.
STIMULUS CONTROL IN A DISCRIMINATION BASED ON A DISTINCTIVE FEATURE1
Authors: Furrow David R. , Lolordo Vincent M.
Published: March 2006

Six pigeons were instrumentally trained to discriminate between two displays that differed only by the presence of a distinctive feature on the positive or food‐correlated display. In accordance with previous studies, subjects learned the discrimination and, in the presence of the positive display, directed most of their responses to the distinctive feature, although responses to the common feature were also reinforced. Subsequent generalization tests revealed that on the positive display, both common and distinctive features produced decremental gradients, contradicting Farthing's (1971) statement that the common feature acquires a control function opposite that of the distinctive feature. Procedural differences probably caused the discrepancy in results; within a display, Farthing presented common and distinctive features successively; the present study used simultaneous presentations of common and distinctive stimuli.
SCHEDULE‐INDUCED DRINKING AS A FUNCTION OF PERCENTAGE REINFORCEMENT1
Authors: Allen Joseph D. , Porter Joseph H. , Arazie Rachelle
Published: March 2006

Drinking was recorded in rats while lever pressing was maintained on a series of percentage reinforcement schedules in which the per cent of 1‐min fixed intervals terminating with food was 100, 90, 30, 70, 10, 50, and 100%. Intervals in which a pellet was omitted were terminated by brief light flash and click stimuli that were also correlated with food presentations. Drinking failed to develop in five of six subjects following intervals in which the brief stimuli were presented regardless of percentage reinforcement. Postpellet drinking, which followed intervals terminated with pellet delivery, however, increased in both duration and amount ingested per interval as percentage reinforcement was systematically decreased. The increase in postpellet drinking above that produced by 100% reinforcement was interpreted as an analogue of the positive‐contrast effect observed with food‐reinforced operants.
REINFORCEMENT CONTINGENCIES AS DISCRIMINATIVE STIMULI1
Authors: Lattal Kennon A.
Published: March 2006

A matching paradigm was used to examine the discriminative properties of two different reinforcement contingencies. Responding according to either a differential‐reinforcement‐of‐low‐rate or a differential‐reinforcement‐of‐other‐behavior schedule produced a choice situation in which each of two keys was illuminated with a unique color. The correct choice response was defined by the contingency that was met to produce the choice. Eighty to 100% correct matching was obtained and recovered during two reversals of the choice stimuli. Introduction of a delay between completion of the reinforcement contingency and presentation of the choice stimuli resulted in decrements in matching performances similar to those obtained when other types of sample stimuli are used. The results provided evidence of the discriminative properties of the relation between behavior and other classes of stimuli.
DISCRIMINABINITY OF FIXED‐RATIO SCHEDULES FOR PIGEONS: EFFECTS OF ABSOLUTE RATIO SIZE1
Authors: Hobson Sally L.
Published: March 2006

In a discrete‐trial choice situation, 12 pigeons were trained to discriminate which of two different fixed ratios they had completed. Psychometric functions were obtained at three ratio requirements (i.e., with the larger ratio set at 10, 20, or 30 responses) by gradually reducing the size of the smaller value. Although different response biases developed across subjects, in each case accuracy decreased systematically with ratio difference regardless of absolute ratio requirements. Above‐chance performances were maintained even at relative ratio differences of 10% or less. Estimates of the Weber fraction showed that, in general, discriminability improved with absolute ratio size up to 30 responses, and beyond, when the results of other studies are considered. A similar trend held for rats studied by other investigators in fixed‐ratio “counting” tasks at lower requirements. In terms of a signal‐detection analysis, performance was similar to that reported for other species and dimensions. Taken together, the results suggest that for this somewhat novel dimension the same psychophysical relations hold as are commonly observed for exteroceptive stimuli.
THE EFFECT OF THE SIZE OF THE TEST ENVIRONMENT ON BEHAVIOR UNDER TWO TEMPORALLY DEFINED SCHEDULES
Authors: Skuban William E. , Richardson W. Kirk
Published: March 2006

The effect of the size of the floor area of the operant test chamber on behavior was tested using a standard‐size test chamber and a test chamber with one‐fourth of the floor area of the standard chamber. Two groups of pigeons were tested under a differential‐reinforcement‐of‐low‐rate 15‐sec schedule or a variable‐interval 60‐sec schedule. Both groups of pigeons had higher response rates while in the smaller floor area. Pigeons under the differential‐reinforcement‐of‐low‐rate schedule also showed a decrease in rate of reinforcement, an increase in ratio of responses to reinforcements, and an alteration in interresponse‐time‐per‐opportunity distributions when tested in the reduced floor‐area condition. These effects are similar to those found under physical restraint, indicating that amount of floor space available for locomotion interacts with schedule behavior and that physical restraint may be regarded as the lower limiting value of amount of floor area available for locomotion.
FIXED‐RATIO ESCAPE AND AVOIDANCE‐ESCAPE FROM NALOXONE IN MORPHINE‐DEPENDENT MONKEYS: EFFECTS OF NALOXONE DOSE AND MORPHINE PRETREATMENT1
Authors: Downs David A. , Woods James H.
Published: March 2006

Lever pressing by rhesus monkeys was maintained by morphine injections during four equally spaced sessions each day. During other periods, lever pressing was maintained by timeout from a continuous naloxone infusion (escape), or by timeout from a stimulus that preceded naloxone injections, or termination of the injections (avoidance‐escape). As naloxone dose increased in the escape procedure, response rate increased to a maximum and then decreased. In the avoidance‐escape procedure, response rate generally increased as naloxone dose increased, but the changes in rate were small compared to the escape procedure. Substitution of saline for naloxone in the escape procedure led to very low response rates within three sessions. In the avoidance‐escape procedure, rate decrements produced by saline substitution appeared to be related to the behavioral history of the monkey. Previous escape experience led to more rapid decreases in responding when saline was introduced, whereas responding was maintained for 15 sessions in a monkey without prior escape conditioning. Morphine pretreatment produced comparable, dose‐dependent decreases in response rates in both procedures. The rate‐decreasing effects of morphine were exacerbated when no naloxone was delivered in the escape procedure.
ECONOMIC AND BIOLOGICAL INFLUENCES ON A PIGEON'S KEY PECK1
Authors: Green Leonard
Published: March 2006

Pigeons were studied in a two‐component multiple schedule. In the first phase of the experiment, key pecks were reinforced on a variable‐interval 2‐min schedule in both components and free food was delivered additionally during one component. When components alternated every 8 sec, all pigeons pecked at a much higher rate during the component with free food than during the other component. At a component duration of 16 min, the reverse was true: all pigeons pecked at a higher rate during the component without free food. In the second phase, the additional food during one component was made contingent on pecking. Responding during the component without the extra food remained essentially unchanged, as expected, since rate of reinforcement remained identical to that in the previous phase. However, rate of responding during the component with the extra food (now contingent on pecking) was elevated, compared to the rate in the first phase, and did not show the marked decline as component duration was increased.
THE MEASUREMENT OF SHARING AND COOPERATION AS EQUITY EFFECTS AND SOME RELATIONSHIPS BETWEEN THEM1
Authors: Hake Don F. , Vukelich Ron , Olvera Dennis
Published: March 2006

The initial objective was to determine whether an increase in cooperative responses (minimal cooperation) was also accompanied by an increase in the degree of correspondence in the number of reinforcers of the two subjects (maximal cooperation). Correct matching‐to‐sample responses of seven pairs of male adolescents were reinforced with money. On each trial, a subject could (1) give the matching‐to‐sample problem to his coactor (give or cooperative responses), or (2) take the problem for himself (take responses). The first member of the pair to respond made the choice. Correspondence did increase under this procedure as compared to a baseline where problems were distributed randomly. However, the increased correspondence usually resulted from take responses rather than cooperative give responses. This equitable method of problem distribution, designated as sharing, was characterized by the subjects alternately taking problems. The spacing of daily sessions may have been partly responsible for the high degree of correspondence, because correspondence did not increase within the usual number of sessions when the sessions were massed, i.e., all in one day. Daily sessions require cooperative responses, i.e., each subject has to show up each day for the other to earn money, and this dependency upon the coactor's behavior may facilitate some sharing or cooperation to ensure the coactor's attendance.
RATIO REQUIREMENT AND REINFORCER EFFECTS IN CONCURRENT FIXED‐INTERVAL FIXED‐RATIO SCHEDULES1
Authors: Wood Keith A. , Martinez Eduardo S. , Willis Richard D.
Published: March 2006

The fixed‐ratio requirement was varied in concurrent fixed‐interval fixed‐ratio schedules. Fixed‐interval responding was reinforced by food. In different phases, fixed‐ratio responding was reinforced by food or water. There was a direct relation between the ratio requirement and interval response rates when both responses were reinforced with food, but essentially no relation when the reinforcers were different. The role of reinforcers in concurrent schedules merits detailed study.
THE PIGEON'S PERCEPTION OF SATURATION1
Authors: Blough Patricia M.
Published: March 2006

Three experiments used similar methods to investigate the pigeon's perception of saturation of monochromatic lights. This trial‐wise procedure consisted of brief presentations of positive and negative stimuli in random sequence. Pecks to the positive stimuli were occasionally reinforced on a low fixed‐ratio schedule. The first study determined absolute thresholds for “white” and monochromatic lights by establishing a discrimination between lights of various radiances and a dark key. Experiment II investigated generalization from a white light to various monochromatic lights under conditions that minimized the use of luminance as a cue. The third experiment examined discrimination of various monochromatic lights along a colorimetric purity continuum; responses to white light were reinforced, while responses to lights that combined white and monochromatic lights in various proportions were not. The results indicated that lights of different wavelength differ in saturation, but that all are discriminable from white. Wavelengths between 550 and 600 nm are least saturated for the pigeon, and saturation increases markedly as wavelength decreases below this region of the spectrum.
PERFORMANCE IN CONCURRENT INTERVAL SCHEDULES: A SYSTEMATIC REPLICATION1
Authors: Lobb Brenda , Davison M. C.
Published: March 2006

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.
RAPID ACQUISITION OF DISCRETE‐TRIAL LEVER‐PRESS AVOIDANCE: EFFECTS OF SIGNAL‐SHOCK INTERVAL1
Authors: Berger David F. , Brush F. Robert
Published: March 2006

Acquisition of discrete‐trial lever‐press avoidance learning was studied in three experiments. Experiment I compared a new training procedure, which produces rates of lever‐press avoidance learning comparable to those obtained in shuttle boxes, with a “conventional”, less efficient training procedure. A factorial design was used to compare continuous versus intermittent shock and a long‐variable versus a short‐fixed signal‐shock interval. Learning was best in the groups trained with the long and variable interval and poorest in those trained with the short and fixed interval. Type of shock had no effect. Experiment II separated the effects of duration from those of variability of the signal‐shock interval. Fixed and variable intervals of 10 and 60 sec were tested and duration was the only significant factor. Experiment III addressed the effect of the differential opportunity to avoid provided by long signal‐shock intervals by varying this interval from 10 to 60 sec in 10‐sec steps. Only the 10‐sec group showed slow acquisition relative to the others. Analysis of avoidance response latencies showed that the distributions for all groups were positively skewed and that skewness increased with increasing duration of the signal‐shock interval. At intervals longer than 20 sec, the animals made progressively less use of their increased opportunity to respond. The data do not support the opportunity‐to‐respond interpretation of the effects of duration of signal‐shock interval and suggest that some type of inhibitory process may block lever‐press avoidance learning at intervals as short as 10 sec. The significance of these findings for species‐specific defense reaction and preparedness theories was emphasized.
STIMULUS‐SPECIFIC CONTRAST EFFECTS DURING OPERANT DISCRIMINATION LEARNING1
Authors: Malone John C.
Published: March 2006

In two experiments, pigeons' responding was equally reinforced in the presence of four line‐orientation stimuli. Responding was then reinforced when only two of the four orientation stimuli were present; the remaining two orientations appeared during extinction. Response rates were often highest in the stimulus adjacent to the orientations presented during extinction and often lowest in that orientation adjacent to the orientations presented with reinforcement. These effects were stronger and more persistent when the stimuli were separated by a smaller angle, rendering the discrimination more difficult. These and other data suggest that discrimination training may not be accurately explained in terms of the simple effects of reinforcement and nonreinforcement associated with isolated stimuli, nor by accounts that depend upon stimulus generalization. Recent accounts of contrast that depend upon “emotionality” produced by nonreinforced responding or upon reinforcement‐elicited responses are also difficult to apply to these data.