bluuebunny/crossref_metadata_2025 huggingface dataset:
GENERALIZATION OF DELAYED IDENTITY MATCHING IN RETARDED CHILDREN
Authors: Lowenkron Barry
Published: March 2006

In an extension of prior research, four retarded children were trained under an identity matching‐to‐sample procedure containing features previously shown to produce controlled generalization to novel stimuli. They first were taught to relate a particular handsign to the sample shape, then to maintain the handsign over a delay interval, and then to select from an array the comparison shape that permitted the handsign to be maintained (i.e., the shape identical to the sample). An initial test revealed little generalization of matching to novel stimuli, but after handsigns were trained to these stimuli, accurate generalized matching appeared immediately. The results replicated prior findings and demonstrated particular features of stimulus control sufficient to enable generalized matching. A behavioral account of relational matching was supported. The technique used in this study was shown to be effective in teaching abstract relations to nonverbal retarded children.
TYPICAL DELAY DETERMINES WAITING TIME ON PERIODIC‐FOOD SCHEDULES: STATIC AND DYNAMIC TESTS
Authors: Wynne C. D. L. , Staddon J. E. R.
Published: March 2006

Pigeons and other animals soon learn to wait (pause) after food delivery on periodic‐food schedules before resuming the food‐rewarded response. Under most conditions the steady‐state duration of the average waiting time, t, is a linear function of the typical interfood interval. We describe three experiments designed to explore the limits of this process. In all experiments, t was associated with one key color and the subsequent food delay, T, with another. In the first experiment, we compared the relation between t (waiting time) and T (food delay) under two conditions: when T was held constant, and when T was an inverse function of t. The pigeons could maximize the rate of food delivery under the first condition by setting t to a consistently short value; optimal behavior under the second condition required a linear relation with unit slope between t and T. Despite this difference in optimal policy, the pigeons in both cases showed the same linear relation, with slope less than one, between t and T. This result was confirmed in a second parametric experiment that added a third condition, in which T + t was held constant. Linear waiting appears to be an obligatory rule for pigeons. In a third experiment we arranged for a multiplicative relation between t and T (positive feedback), and produced either very short or very long waiting times as predicted by a quasi‐dynamic model in which waiting time is strongly determined by the just‐preceding food delay.
RESPONSE RESTRICTION AND SUBSTITUTION WITH AUTISTIC CHILDREN
Authors: Green Gina , Striefel Sebastian
Published: March 2006

Few studies to date have examined time reallocation in naturalistic, multiresponse human repertoires when one or more responses are restricted. For this experiment, free‐operant baseline levels of six responses were measured for four autistic children. The high‐probability responses were made unavailable, one at a time, such that subjects had access to five, four, three, and two responses in successive restriction conditions. A return to the six‐response free‐operant baseline condition completed the experiment. Results were compared to predictions made by four time‐reallocation models. These results were described accurately only by the selective substitution model. Further analyses examined alternative explanations for the individual reallocation patterns obtained. An expanded selective substitution definition is proposed that may characterize orderly patterns observed in multiresponse repertoires under restriction conditions more accurately than the other existing models.
DELAY OF REINFORCERS IN A CONCURRENT‐CHAIN SCHEDULE: AN EXTENSION OF THE HYPERBOLIC‐DECAY MODEL
Authors: Davison Michael
Published: March 2006

Six pigeons were trained in concurrent‐chain schedules with equal aperiodic initial links and delays to reinforcers in the terminal links. The terminal links always lasted 30 s. In Experiment 1, two reinforcers were delivered in each terminal link, with the first reinforcer delivered either 1 s (Experiment 1A) or 5 s (Experiment 1B) after choice. In these experiments, the delay between the first and second reinforcers in one terminal link was 10 s, and the delay between the first and second reinforcers on the other key was varied. This variation produced little change in preference. In Experiment 1C, the first and second delays on one key were 10 s, and on the other key they were varied within the restriction that the sum of delays was 20 s. Preference for the varied terminal link increased as the first delay was decreased. A hyperbolic model of the value of reinforcer delay provided a good description of the data from Experiment 1. In Experiment 2, a single reinforcer was delivered in each terminal link after a delay of either 0.2 or 19.8 s, and these delays were reversed between conditions. The initial‐link schedule providing terminal‐link access was varied from means of 5 s to 480 s. As the initial‐link duration was increased, preference for the shorter delay became less extreme. An extension of the hyperbolic‐decay model, in which the decay constant was a hyperbolic function of the initial‐link duration, described the results well. Differences between the procedure used here (constant‐duration terminal links) and that used in conventional concurrent‐chain research precludes use of the model as a general account of concurrent‐chain performance.
THE INTEGRATION OF HABITS MAINTAINED BY FOOD AND WATER REINFORCEMENT THROUGH STIMULUS COMPOUNDING
Authors: Weiss Stanley J. , Schindler Charles W. , Eason Ramona
Published: March 2006

In Experiment 1, a light and a tone were correlated independently with water reinforcement of bar pressing by rats. With different naive subjects in Experiment 2, one of these stimuli was correlated with food and the other with water reinforcement (counterbalanced). In both experiments the absence of tone and light signaled extinction. Tests of stimulus‐reinforcer independence in Experiment 2 indicated that tone and light controlled behavior whose rate was specifically affected by deprivation state. In the stimulus‐compounding tests of both experiments, response rates were higher to tone‐plus‐light than to tone or light presented alone (additive summation). This is the first report of additive summation produced through compounding stimuli paired with different reinforcers. The results are discussed in the context of the effects of incentive motivation on operant performance.
EFFECTS OF ALTERNATIVE REINFORCEMENT SOURCES: A REEVALUATION
Authors: Imam Abdulrazaq A. , Lattal Kennon A.
Published: March 2006

The effects of two alternative sources of food delivery on the key‐peck responding of pigeons were examined. Pecking was maintained by a variable‐interval 3‐min schedule. In the presence of this schedule in different conditions, either a variable‐time 3‐min schedule delivering food independently of responding or an equivalent schedule that required a minimum 2‐s pause between a key peck and food delivery (a differential‐reinforcement‐of‐other‐behavior schedule) was added. The differential‐reinforcement‐of‐other‐behavior schedule reduced response rates more than did the variable‐time schedule in most instances. The delay between a key peck and the next reinforcer consistently was longer under the differential‐reinforcement‐of‐other‐behavior schedule than under the variable‐time schedule. Response rates and median delay between responses and reinforcers were negatively correlated. These results contradict earlier conclusions about the behavioral effects of alternative reinforcement. They suggest that an interpretation in terms of response—reinforcer contiguity is consistent with the data.
SIGNALED AVOIDANCE IN THE EYE WITHDRAWAL REFLEX OF THE GREEN CRAB
Authors: Abramson Charles I. , Armstrong Philip M. , Feinman Robin A. , Feinman Richard D.
Published: March 2006

Learning in a signaled avoidance procedure was studied in the eye withdrawal reflex of the green crab, Carcinus maenas. A puff of air to the eye, which causes eye retraction, was used as the unconditioned stimulus (US). A mild vibration on the carapace, which has no effect on untrained animals, was used as a warning (conditioned) stimulus (CS). Eye withdrawal during the CS led to the omission of the otherwise scheduled US. Acquisition was rapid, reaching about 75% avoidance after 30 trials. Extinction occurred slowly over the course of 40 CS‐only trials. Yoked controls did not perform as well. The behavior of experimental animals in the avoidance procedure was found to be essentially identical to the performance of animals subjected to a classical conditioning paradigm in which CS responses had no effect on US presentation. Additional groups of animals were subjected to experiments in which (a) avoidance conditioning (60 trials) was followed by classical conditioning (40 trials) or (b) classical conditioning was followed by avoidance. The behavior of these groups was, again, essentially identical. The results suggest that there may be an underlying Pavlovian mechanism for the learned response, although the contribution of an operant process is not excluded. The results expand the range of invertebrate animals in which fundamental conditioning phenomena can be demonstrated, and may provide a neuronal model for learning in a signaled avoidance procedure.
CONDITIONING OF APPETITIVE AND CONSUMMATORY SEXUAL BEHAVIOR IN MALE JAPANESE QUAIL
Authors: Domjan Michael , O'Vary Deborah , Greene Paul
Published: March 2006

Two different types of stimulus objects, a live female quail artificially adorned with bright orange feathers and an inanimate toy dog, served as conditioned stimuli. For subjects in experimental groups, the conditioned stimuli were presented shortly before access to a sexually receptive normal female quail. For subjects in control groups, exposure to the conditioned stimuli was unpaired with copulatory opportunity. Subjects in the experimental but not in the control groups quickly came to approach the location of the conditioned stimulus objects. When an adorned female quail served as the conditioned stimulus, the conditioned approach behavior was controlled by a combination of the presence of the orange adornments and the visual cues of the head and neck of the female bird, and the approach behavior persisted as the adorned female moved to new locations. When the toy dog served as the conditioned stimulus, the conditioned approach behavior was limited to the spatial cues that surrounded the toy dog during conditioning trials. Although both types of stimulus objects evoked conditioned approach behavior, only the adorned female stimulus supported copulatory behavior. This last finding indicates that copulatory behavior can become redirected toward novel stimuli as a result of conditioning, but only under special circumstances. The results are consistent with the suggestion that appetitive components of reproductive behavior are more susceptible to conditioning than consummatory components. Possible reasons for this are discussed, together with implications of the results for the contribution of conditioning processes to sexual selection.
CONTROL OF RESPONDING BY SOUNDS OF DIFFERENT QUALITY: AN EVOLUTIONARY ANALYSIS
Authors: Harrison J. M.
Published: March 2006

Two experiments investigated the acquisition of discriminations between two acoustic stimuli of different quality (noise bursts vs. a 2‐kHz pulsed signal) when features of the everyday environment were incorporated into the experiments. In Experiment 1, rats were trained, using food, to press a lever. Throughout all sessions, 5‐s trials of noise bursts (the random stimulus) were presented, after variable intertrial intervals, through a remote speaker mounted outside the experimental enclosure. The noise bursts occurred randomly with respect to reinforcement of lever pressing and had no programmed relationship to the animal's behavior. When lever pressing was established, the 2‐kHz signal was presented through a speaker adjacent to the response lever according to a different set of variable intertrial intervals. A response in the presence of the 2‐kHz signal terminated the trial and was reinforced. The 2‐kHz signal acquired control of responding within the first few trials, whereas the random stimulus exerted no control of responding. In Experiment 2, rats were trained to press the lever in the presence of the 2‐kHz signal presented through the adjacent speaker on a variable intertrial interval. After 14 sessions, 5‐s trials of noise bursts (random stimulus) were presented through the remote speaker on the second variable intertrial interval. The random stimulus initially elicited exploratory behavior, which then rapidly declined. Subsequently, the random stimulus exerted no or weak control of responding. The introduction of the random stimulus had no effect on responding in the presence of the adjacent stimulus.

In Experiments 3 and 4 the random stimulus was presented through the adjacent speaker, and the stimulus correlated with reinforcement was presented through the remote speaker. In both experiments, there was persistent control of responding by the random stimulus and slow development of control by the stimulus correlated with reinforcement. In Experiment 5, both stimuli were presented through the adjacent speaker. There was persistent control of responding by the random stimulus.
PIGEONS CAN DISCRIMINATE LOCATIONS PRESENTED IN PICTURES
Authors: Honig W. K. , Stewart Karen E.
Published: March 2006

The present experiments were designed to teach pigeons to discriminate two locations represented by color photographs. Two sets of photographs were taken at two distinctive locations on a university campus. These sets represented several standpoints at each location. For the true‐discrimination group, pictures from the two locations were differentially associated with reward; for the pseudodiscrimination group, half of the views from each location were arbitrarily but consistently associated with reward. The former group acquired the discrimination much more rapidly. These birds also showed good transfer to new views from the standpoints used in training and to a new standpoint at each location not used in training. In a second experiment, another group of pigeons could terminate any training trial by pecking an “advance” key. Three of 4 subjects used this option to reduce the duration of trials in which pictures from the negative location were presented. These data suggest that pigeons can integrate views shown in pictures into a “concept” of a location. The method used here may be the experimental analogue of a common, natural process by which animals learn to identify locations.
COMPREHENSION OF “ABSENCE” BY AN AFRICAN GREY PARROT: LEARNING WITH RESPECT TO QUESTIONS OF SAME/DIFFERENT
Authors: Pepperberg Irene M.
Published: March 2006

An African Grey parrot, Alex, learned to report on the absence or presence of similarity and difference between two objects. Alex was shown pairs of objects that were (a) totally dissimilar, (b) identical, or (c) similar or different with respect to one of three attributes (color, shape, or material). In the first two cases, he responded to the respective queries of “What's same?” or “What's different?” with the vocalization “none,” and in the third case he responded with the appropriate category label (“color,” “shape,” or “mah‐mah” [matter]). His accuracy was 80.9% to 83.9% for pairs of familiar objects not used in training and 72.5% to 78.4% for pairs whose colors, shapes, and materials were unfamiliar. The data provide evidence that this parrot's abilities are comparable to those of mammals that have been trained to report on the presence or absence of objects or features of objects.
ORAL SELF‐ADMINISTRATION OF PENTOBARBITAL BY RHESUS MONKEYS: RELATIVE REINFORCING EFFECTS UNDER CONCURRENT FIXED‐RATIO SCHEDULES
Authors: Meisch Richard A. , Lemaire Gregory A.
Published: March 2006

During daily 3‐hr sessions, orally delivered pentobarbital solutions and water, or two separate pentobarbital solutions, were concurrently available to rhesus monkeys according to fixed‐ratio schedules of mouth contacts with a spout. First water, and then each of four “comparison‐concentration” pentobarbital solutions (0.0625, 0.25, 1, and 4 mg/mL), was successively available from one spout for a block of sessions under a fixed‐ratio‐64 (three monkeys) or fixed‐ratio‐16 (one monkey) schedule. Under an identically sized fixed‐ratio schedule, deliveries of a “standard‐concentration” pentobarbital solution were concurrently available from a second spout. The concentration of the standard solution remained unchanged throughout testing of the series of comparison solutions. Each of three pentobarbital concentrations (4, 1, and 0.25 mg/mL) in turn served as the standard concentration. Within each pair of concurrently available solutions, the higher drug concentration maintained more behavior than the lower concentration. Thus when monkeys were provided with concurrent access to different pentobarbital concentrations, relative reinforcing effects were directly related to drug concentration. Further, the amount of behavior maintained by a particular drug concentration was dependent on the concentration of the concurrently available drug solution. Thus, the relative effectiveness of a reinforcer in maintaining behavior is a function of both the reinforcer's magnitude and the availability of alternative reinforcers in the environment.
RESPONSE—REINFORCER CONTINGENCY AND SPATIALLY DEFINED OPERANTS: TESTING AN INVARIANCE PROPERTY OF PHI
Authors: Galbicka Gregory , Platt John R.
Published: March 2006

A chamber containing 72 response keys defining the circumference of a circle 1 m in diameter was used to examine the relation between differentiation of response location and a measure of response‐reinforcer contingency known as the phi coefficient. A different target key was specified in each successive phase, and response location was differentiated with respect to the target. Criterional and noncriterional responses (i.e., responses “near” and “far” from the target) were defined using targeted percentile schedules to control the overall probability of each response class. By manipulating criterional (and, hence, noncriterional) response probability and the reinforcement probabilities conditional on each, a mathematical in variance property peculiar to phi in contingency analysis was examined. Specifically, diagonally interchanging cell frequencies in a 2 × 2 table relating criterional/noncriterional responses to reinforcement/nonreinforcement leaves phi unchanged. Hence, the degree of response differentiation predicted by phi remains unchanged under the four permutations implied by the various diagonal interchanges. This predicted invariance was examined under values of phi equal to .33, .58, and .82. Increasing phi generally increased the stereotypy of response location. Three of the permutations generated almost interchangeable performance at different phi values. The remaining permutation, however, generated functions relating response concentration to phi with slopes shallower than those obtained under the other permutations. This resulted from relatively higher levels of differentiation, compared to the other permutations, at low phi values. These data strongly suggest boundary conditions on the ability of phi to reflect completely the local processes that are indexed by phi at a molar level.
THE APPLICATION OF HERRNSTEIN'S LAW OF EFFECT TO DISRUPTIVE AND ON‐TASK BEHAVIOR OF A RETARDED ADOLESCENT GIRL
Authors: Martens Brian K. , Houk Jack L.
Published: March 2006

The purpose of the present study was to evaluate Herrnstein's law of effect as a description of socially significant behavior in an applied setting. The subject was an 18‐year‐old retarded girl with a history of autistic‐like and aggressive behavior. Using a baseline design for two response classes and stimulus conditions, eight categories of subject and staff behavior were monitored over a 3‐week period. A computerized observation system, developed for use in the present investigation, was used to obtain real‐time durations of the behavior categories alone and in combination. Overlapping durations of teacher and subject behavior were then correlated to yield approximations to a functional definition of reinforcement. Plots of behavior by contingent reinforcement revealed a hyperbolic relationship for each response class, the shape of which varied as a function of extraneous reinforcement r0. In addition, estimated parameters in Herrnstein's equation did not differ significantly from those obtained through independent observation. Finally, Herrnstein's equation accounted for an average 63% of variance in response allocation. Results are discussed in terms of the relevance of matching‐law theory to behavior in applied settings.
DISCRETE AND CONTINUOUS MEASURES OF DIMENSIONAL STIMULUS CONTROL
Authors: Hinson John M. , Higa Jennifer J.
Published: March 2006

In two sets of experiments, we examined dimensional stimulus control of pigeons' responses to a visual flicker‐rate continuum. In the first experiment, responses to a single key were reinforced periodically during stimuli from one half of the stimulus continuum, and responses during other stimuli were extinguished. In the second experiment, two response keys were simultaneously available, with reinforcement for each response alternative associated with different halves of the stimulus continuum. Conditions of the second experiment involved either free‐operant or discrete‐trial stimulus presentations. Results from these experiments show that positive dimensional contrast appeared in discrimination tasks with one or two response alternatives, but only with free‐operant procedures. In addition, discrimination between stimulus classes established by differential reinforcement was assessed as accurately by continuous rate measures as by discrete response choice in the two‐alternative situation. The general implication of these experiments is that response rate measures, when properly applied, may reveal sources of variation within stimulus classes, such as dimensional contrast, that are not evident with discrete measures.
SENSITIVITY OF TIME ALLOCATION TO AN OVERALL REINFORCER RATE FEEDBACK FUNCTION IN CONCURRENT INTERVAL SCHEDULES
Authors: Davison Michael , Kerr Andrew
Published: March 2006

Six pigeons were trained on concurrent variable‐interval schedules in which feedback functions arranged that the overall reinforcer rate either (a) was independent of preference, (b) decreased with increasing absolute preference, or (c) increased with increasing absolute preference. In Experiment 1, the reinforcer rate in an interreinforcement interval was determined by the absolute time‐allocation ratio in the previous interval. When arranged reinforcer ratios were varied, there was no evidence of control over preference by overall reinforcer rate. In Experiment 2, the feedback function arranged that reinforcer rates were an inverse function of absolute preference, and window durations were fixed times. In Phase 1, using schedules that provided a four‐to‐one reinforcer ratio, the window duration was decreased from 20 s to 5 s over four conditions. Then, in Phases 2 and 3, the arranged reinforcer ratios were varied. In Phase 2, the reinforcer rate in the current 5‐s time window was determined by preference in the previous 5‐s window, and in Phase 3, the window durations were 20 s. Again, there was no indication of control by obtained overall reinforcer rate. These data call into question theories that suggest that the process underlying matching is one of maximizing overall reinforcer rates, or that preference in concurrent aperiodic schedules is controlled to any extent by overall reinforcer rate. They also question the notion that concurrent‐schedule preference is controlled by molecular maximizing.
DISCRIMINATION THEORY OF RULE‐GOVERNED BEHAVIOR
Authors: Cerutti Daniel T.
Published: March 2006

In rule‐governed behavior, previously established elementary discriminations are combined in complex instructions and thus result in complex behavior. Discriminative combining and recombining of responses produce behavior with characteristics differing from those of behavior that is established through the effects of its direct consequences. For example, responding in instructed discrimination may be occasioned by discriminative stimuli that are temporally and situationally removed from the circumstances under which the discrimination is instructed. The present account illustrates properties of rule‐governed behavior with examples from research in instructional control and imitation learning. Units of instructed behavior, circumstances controlling compliance with instructions, and rule‐governed problem solving are considered.
EFFECTS OF RELATIVE REINFORCER FREQUENCY ON COMPLEX COLOR DETECTION
Authors: Davison Michael , McCarthy Dianne
Published: March 2006

Pigeons were trained under a discrete‐trials detection procedure in which one of a set of color stimuli was presented on the center key and a single response turned off the stimulus and illuminated two side keys. Single responses to one or the other side key produced occasional reinforcers depending on the value of the color stimulus. In Experiment 1, one color‐stimulus set comprised 559, 564, 569, and 574 nm, and right‐key pecks were occasionally reinforced following presentations of members of this set. The other stimulus set comprised 579, 584, 589, and 594 nm, and left‐key pecks were occasionally reinforced following presentations of members of this set. Across seven experimental conditions, the left/(left + right) relative reinforcer frequency was varied from .1 to .9. In Experiment 2, one stimulus set contained only one member, 574 nm, and right‐key responses were occasionally reinforced following its presentation. Over 12 experimental conditions, two manipulations were carried out. First, the number of stimuli comprising the other stimulus set was increased from one (579 nm) to two (579 and 584 nm) to three (579, 584, and 589 nm) and to four (579, 584, 589, and 594 nm), and left‐key responses were reinforced occasionally following center‐key presentations of members of this set. Second, for each stimulus combination, the left/(left + right) relative reinforcer frequency was varied from .1 to .5 to .9 across three experimental conditions. The principal finding of Experiments 1 and 2 was that reinforcers and stimuli interacted in their effects on behavior. In Experiment 3, pairs of adjacent stimuli (5 nm apart) in the range 559 to 594 nm were presented in each experimental condition, and the left/(left + right) relative reinforcer frequency was held constant at .5. The data from all three experiments were analyzed according to a detection model describing performance in multiple‐stimulus two‐response procedures. This model provided independent measures of stimulus discriminability, contingency discriminability, and bias. The analysis showed that (a) consistent with the color‐naming function, pigeons were better able to discriminate between higher nanometer values than lower nanometer values; (b) their ability to discriminate between the stimuli was independent of the number of wavelengths comprising each stimulus set; (c) they allocated delivered reinforcers very accurately to the previously emitted response; and (d) no consistent biases emerged.
RESPONDING ON CONCURRENT‐CHAINS SCHEDULES IN OPEN AND CLOSED ECONOMIES
Authors: Lafiette Michael H. , Fantino Edmund
Published: March 2006

Pigeons' key pecks were reinforced according to concurrent‐chains schedules of reinforcement. The programmed average time from the onset of the initial links to a terminal link entry was held constant across conditions while the value of variable‐interval schedules in the terminal links was varied. Performance was assessed under two economic conditions: (a) an open economy in which session duration was limited to 1 hr and subjects were maintained at 80% of their free‐feeding body weights with postsession food when necessary; and (b) a closed economy in which sessions were 23.5 hr long and no deprivation regimen was in effect. In all cases, the relative rate of responding in the initial links matched the reduction in overall delay to primary reinforcement correlated with entry into one terminal link relative to the reduction in delay correlated with entry into the other terminal link. Although the sum of responses made in the initial links and terminal links was found to increase, then decrease, as the rate of food presentation decreased in the closed economy, there was no consistent effect of overall rate of food presentation on total responding in the open economy. The choice data suggest that relative delay reduction predicts choice accurately, regardless of economic context.
CORRESPONDENCE IN CHILDREN'S SELF‐REPORT: TACTING AND MANDING ASPECTS
Authors: Ribeiro Antonio de Freitas
Published: March 2006

Four boys and 4 girls (3 to 5 years old) played with as many as three toys chosen from a set of six, and were then asked whether they played with each of the toys. After a baseline in which all children showed high levels of correspondence between reported and actual behavior, reports of play were differentially reinforced, first in an individual and then in a social context. Two children in the individual condition began to report play with all six toys, even though no more than three toys had been played with. When reports of play were reinforced in a group context, 5 children reported play with all six toys. When correspondence was subsequently reinforced, virtually complete correspondence returned and was maintained in a third noncontingent reinforcement condition. Correspondence and lack of correspondence were discussed in terms of self‐tacting and distorted tacting or manding.
TRANSFER OF CONTEXTUAL STIMULUS FUNCTION VIA EQUIVALENCE CLASS DEVELOPMENT
Authors: Gatch Michael B. , Osborne J. Grayson
Published: March 2006

In a conditional discrimination, 6 college students arranged six Cyrillic letters into groups of three based upon which of two additional Cyrillic letters (contextual stimuli) was present. All subjects demonstrated symmetry and transitivity within each class of equivalent stimuli. In a second conditional discrimination, two more Cyrillic letters were related to each contextual stimulus. Testing of symmetrical and transitive relations between the original contextual stimulus and the two new ones confirmed the development of two three‐member classes of contextual stimuli. Subsequent tests demonstrated that the new contextual stimuli controlled the previously trained sample‐comparison relations for all subjects.
CHILDREN'S IDENTITY MATCHING AND ODDITY: ASSESSING CONTROL BY SPECIFIC AND GENERAL SAMPLE‐COMPARISON RELATIONS
Authors: Stromer Robert , Stromer Joan Butcher
Published: March 2006

After children in Experiments 1 and 2 learned identity matching or oddity, control by sample‐comparison relations was assessed. Tests for generalized control displayed novel samples and two comparison stimuli, one identical to the sample. Specific relations were tested with identical or nonidentical sample‐comparison stimuli from one set of stimuli and substitute comparisons from either the other training set or from a novel set. When tests displayed identical stimuli, patterns of comparison selection suggested control by generalized identity and oddity. However, selection patterns varied when stimuli were nonidentical and familiar or novel substitute comparisons were used. Therefore, control by specific relations is not a precondition for generalized identity and oddity. One set of training stimuli was used in Experiment 3, and generalized performances occurred again. Moreover, control by specific relations was shown by the oddity subjects and 2 of 6 identity subjects. Generalized and specific control may therefore exist simultaneously. In Experiment 4, selections were irregular on tests displaying substitute comparisons and samples and familiar comparison stimuli; this finding supported the relational account of specific sample‐comparison control found in Experiment 3.
STIMULUS CLASS FORMATION AND STIMULUS—REINFORCER RELATIONS
Authors: Dube William V. , McIlvane William J. , Maguire Russell W. , Mackay Harry A. , Stoddard Lawrence T.
Published: March 2006

This study examined stimulus class membership established via stimulus—reinforcer relations. Mentally retarded subjects learned conditional discriminations with four two‐member sets of visual stimuli (A, B, C, and D). On arbitrary‐matching trials, they selected comparison stimuli B1 and B2 conditionally upon samples A1 and A2, respectively, and C1 and C2 conditionally upon B1 and B2, respectively. On identity‐matching trials, they selected all stimuli as comparisons conditionally upon identical stimuli as samples. Throughout training, correct selections of A1, B1, C1, and D1 were followed by one reinforcer, R1, and those of A2, B2, C2, and D2 were followed by another, R2. Subsequent tests documented the formation of two four‐member stimulus classes, A1‐B1‐C1‐D1 and A2‐B2‐C2‐D2. The class membership of the A, B, and C stimuli could have been based on equivalence relations that resulted from the arbitrary‐matching training. D1 and D2 had never appeared on arbitrary‐matching trials, however. Their class membership must have been based on relations with R1 and R2, respectively. Results thus confirm a previous finding that stimulus classes can be expanded via stimulus—reinforcer relations. They also define more precisely the potential nature of those classes and the conditions under which class membership can be established.
EFFECTS OF METHADONE ON ALTERNATIVE FIXED‐RATIO FIXED‐INTERVAL PERFORMANCE: LATENT INFLUENCES ON SCHEDULE‐CONTROLLED RESPONDING
Authors: Egli Mark , Thompson Travis
Published: March 2006

Effects of methadone on pigeons' key pecking were examined under four conditions selected to analyze the control of behavior under alternative fixed‐ratio fixed‐interval schedules. In Condition 1, pigeons pecked under one of three different alternative schedules (alternative fixed‐ratio 50 fixed‐interval 90 s, alternative fixed‐ratio 75 fixed‐interval 90 s and alternative fixed‐ratio 200 fixed‐interval 90 s) each week. In Condition 2, fixed‐ratio 50 or fixed‐ratio 75 schedules were in effect during baseline sessions, and alternative fixed‐ratio 50 fixed‐interval 90‐s or alternative fixed‐ratio 75 fixed‐interval 90‐s schedules were in effect during sessions in which methadone was administered. In Condition 3, effects of methadone on key pecking maintained under fixed‐ratio 50 and fixed‐ratio 75 schedules were examined, whereas in Condition 4 the effects of methadone on key pecking under a fixed‐interval 90‐s schedule as well as fixed‐ratio 50 and fixed‐ratio 75 schedules were investigated. Control by the fixed‐interval contingency was assessed by computing the proportion of total session reinforcers delivered under the fixed‐interval schedule. Methadone administration (0.5–4.0 mg/kg) shifted the predominant source of schedule control under the alternative schedule from the fixed‐ratio schedule to the fixed‐interval contingency. This shift was dependent on methadone dose and fixed‐ratio size. Control by the fixed‐interval contingency was greatest following extensive exposure to the interval component embedded within the alternative schedule (Condition 1), but was apparent to a lesser degree with even very limited exposure to the alternative fixed‐ratio fixed‐interval schedule (Condition 2). Interreinforcement intervals comparable to those under a fixed‐interval schedule were not observed under the fixed‐ratio schedules presented alone (Condition 3). Repeated exposure to the fixed‐interval contingency outside the context of the alternative fixed‐ratio fixed‐interval schedule did not engender performance changes under a fixed‐ratio schedule which would mimic those of increased fixed‐interval contingency control (Condition 4). These data suggest that drug administration can be used to unmask the influence of contingencies that are latent under baseline conditions and reveal influences of both past and present environmental variables.
OPERANT CONDITIONING OF BEHAVIORAL VARIABILITY USING A PERCENTILE REINFORCEMENT SCHEDULE
Authors: Machado Armando
Published: March 2006

The present investigation developed and tested a new percentile reinforcement schedule suited to study pattern variability, whose main feature was the relative dissociation it provided between the variability requirement defining criterional responses and overall probability of reinforcement. In a discrete‐trials procedure, pigeons produced patterns of four pecks on two response keys. If the pattern emitted on the current trial differed from the N preceding patterns, reinforcement was delivered with probability u. The schedule continuously adjusted the criterion N such that the probability of a criterional response, estimated from the subject's recent behavior, was always constant. In these circumstances, the criterion corresponded to an invariant percentile in the distribution of recent responses.

Using a between‐subjects design, Experiment 1 manipulated the variability requirement—the percentile—while keeping overall reinforcement probability constant. The degree of variability varied directly with the requirement. In addition, an inverse relationship existed between the requirement and within‐group variance. Experiment 2 manipulated probability of reinforcement while maintaining the variability requirement constant. No consistent relationship was found between variability and reinforcement probability. A tentative hypothesis was advanced ascribing the operant conditioning of behavioral variability to a process of probability‐dependent selection.
ON THE LIMITS OF THE MATCHING CONCEPT IN MONKEYS (CEBUS APELLA)
Authors: D'Amato M. R. , Colombo Michael
Published: March 2006

Two cebus monkeys, with many years of experience matching a variety of static visual stimuli (forms and colors) within a standard matching‐to‐sample paradigm, were trained to press a left lever when a pair of displayed static stimuli were the same and to press a right lever when they were different. After learning the same/different task, the monkeys were tested for transfer to dynamic visual stimuli (flashing versus steady green disks), with which they had no previous experience. Both failed to transfer to the dynamic stimuli. A third monkey, also with massive past experience matching static visual stimuli, was tested for transfer to the dynamic stimuli within our standard matching paradigm, and it, too, failed. All 3 subjects were unable to reach a moderate acquisition criterion despite as many as 52 sessions of training with the dynamic stimuli. These results provide further evidence that, in monkeys, the matching (or identity) concept has a very limited reach; they consequently do not support the view held by some theorists that an abstract matching concept based on physical similarity is a general endowment of animals.
SHORT‐TERM MEMORY FOR RESPONSES: THE “CHOOSE‐SMALL” EFFECT
Authors: Fetterman J. Gregor , Macewen David
Published: March 2006

Pigeons' short‐term memory for fixed‐ratio requirements was assessed using a delayed symbolic matching‐to‐sample procedure. Different choices were reinforced after fixed‐ratio 10 and fixed‐ratio 40 requirements, and delays of 0, 5, or 20 s were sometimes placed between sample ratios and choice. All birds made disproportionate numbers of responses to the small‐ratio choice alternative when delays were interposed between ratios and choice, and this bias increased as a function of delay. Preference for the small fixed‐ratio alternative was also observed on “no‐sample” trials, during which the choice alternatives were presented without a prior sample ratio. This “choose‐small” bias is analogous to results obtained by Spetch and Wilkie (1983) with event duration as the discriminative stimulus. The choose‐small bias was attenuated when the houselight was turned on during delays, but overall accuracy was not influenced systematically by the houselight manipulation.
USE OF AN AMBIGUOUS‐SAMPLE PROCEDURE TO ESTABLISH A CUE TO FORGET IN PIGEONS
Authors: Grant Douglas S.
Published: March 2006

Pigeons were trained on a variation of the matching‐to‐sample task in which on double‐sample trials two samples, one associated with each of the comparison stimuli, were presented successively. Responding to the comparison associated with the first sample was reinforced on half the double‐sample trials, and responding to the comparison associated with the second sample was reinforced on the remaining half. One of two postsample stimuli was presented following the termination of each colored sample. A vertical line was presented after a correct or target sample, and a horizontal line was presented after an incorrect or interfering sample. With extended training, each bird demonstrated above‐chance accuracy on double‐sample trials, providing prima facie evidence that one or both of the postsample stimuli exerted control over matching behavior. Experiment 2 provided evidence that the horizontal line functioned as a cue to forget the code activated by the preceding sample stimulus. It was concluded that a condition sufficient to establish a postsample stimulus as a cue to forget is that the postsample immediately follow presentation of a sample that, if it were to control test responding, would lead to nonreinforcement.
ON CONDITIONED REINFORCING EFFECTS OF NEGATIVE DISCRIMINATIVE STIMULI
Authors: Allen Keith D. , Lattal Kennon A.
Published: March 2006

Observing responses by pigeons were studied during sessions in which a food key and an observing key were available continuously. A variable‐interval schedule and extinction alternated randomly on the food key. In one condition, food‐key pecking during extinction decreased reinforcement frequency during the next variable‐interval component, and in the other condition such pecking did not affect reinforcement frequency. Observing responses either changed both keylight colors from white to green (S+) or to red (S‐) depending on the condition on the food key, or the observing responses never produced the S+ but produced the S‐ when extinction was in effect on the food key. Observing responses that produced only S‐ were maintained only when food‐key pecking during extinction decreased reinforcement frequency in the subsequent variable‐interval component. The red light conformed to conventional definitions of a negative discriminative stimulus, rendering results counter to previous findings that production of S‐ alone does not maintain observing. Rather than offering support for an informational account of conditioned reinforcement, the results are discussed in terms of a molar analysis to account for how stimuli acquire response‐maintaining properties.
VISUALLY GUIDED CATCHING AND TRACKING SKILLS IN PIGEONS: A PRELIMINARY ANALYSIS
Authors: Rilling Mark E. , Laclaire Thomas L.
Published: March 2006

Research on reaching, tracking, and catching in the pigeon has been hampered by limitations of technology. A new system was developed in which the target was a small rectangle presented on a video display terminal and the pecking response was detected with touch technology. The target moved up and down vertically with sinusoidal velocity. A coincidence between the location of the pigeon's beak and the cursor produced reinforcement. The pigeon pecked ahead and behind the target, but most pecks occurred behind the target so the dominant tracking strategy was lagging. The pigeon was adept at “catching” the target at many locations throughout the trajectory. Transfer of motor learning was tested on probe trials during which the trajectory changed from vertical to horizontal. On transfer trials the pigeons' dominant pattern of pecking immediately shifted from vertical to horizontal. The motor skill displayed by the pigeons was flexible and adaptive, suggesting that the pigeons had learned to track the cursor.
NONHUMAN SHORT‐TERM MEMORY: A QUANTITATIVE REANALYSIS OF SELECTED FINDINGS
Authors: Wixted John T.
Published: March 2006

Intense interest in the experimental analysis of nonhuman short‐term memory was occasioned by the “cognitive revolution” in the early 1970s. As researchers tested and refined their theoretical models, a sizable empirical literature on the subject rapidly emerged. Generally missing from that literature, however, is an integrated account of the empirical laws of delayed stimulus control. In its absence, cognitive theories have grown increasingly complex and their connection to established principles of learning more remote. The present article reviews a representative segment of the nonhuman memory literature in an effort to identify and tentatively quantify empirical laws that may underlie some of the major findings. Specifically, a delay‐reduction principle adapted from the conditioned reinforcement literature and a proposed principle of serial stimulus compounds were evaluated against data from delayed matching to sample, serial probe recognition, differential outcome, directed forgetting, and surprisingness preparations. Although by no means offering a complete description of the data, the proposed analysis organizes an apparently disparate collection of empirical results and suggests several new lines of inquiry into the subject.
THE EFFECT OF LOGARITHMIC TRANSFORMATION ON ESTIMATING THE PARAMETERS OF THE GENERALIZED MATCHING LAW
Authors: Heth C. Donald , Pierce W. David , Belke Terry W. , Hensch S. A.
Published: March 2006

The generalized matching law was initially stated as a nonlinear relation between reinforcement‐rate ratios and response‐rate ratios. Often, the variables of the law are transformed logarithmically to remove the nonlinearity; empirical results are then fit to the model through least‐squares regression. However, the logarithmic expression of the matching law is a biased statistical representation of the law itself. In particular, the logarithmic transformation alters the quantitative conclusions to be drawn from a least‐squares regression analysis. A Monte Carlo study of the effect of transforming matching‐law data demonstrated that (a) the estimates of one or both of the parameters of the generalized matching law are biased, (b) the measure of goodness of fit (R2) is inaccurate, and (c) predictions generated by the fitted parameters are incorrect. Alternative approaches to logarithmic transformations are shown to alleviate these problems.
DETERMINANTS OF CHOICE FOR PIGEONS AND HUMANS ON CONCURRENT‐CHAINS SCHEDULES OF REINFORCEMENT
Authors: Belke Terry W. , Pierce W. David , Powell Russell A.
Published: March 2006

Concurrent‐chains schedules of reinforcement were arranged for humans and pigeons. Responses of humans were reinforced with tokens exchangeable for money, and key pecks of 4 birds were reinforced with food. Variable‐interval 30‐s and 40‐s schedules operated in the terminal links of the chains. Condition 1 exposed subjects to variable‐interval 90‐s and variable‐interval 30‐s initial links, respectively. Conditions 2 and 3 arranged equal initial‐link schedules of 40 s or 120 s. Experimental conditions tested the descriptive adequacy of five equations: reinforcement density, delay reduction, modified delay reduction, matching and maximization. Results based on choice proportions and switch rates during the initial links showed that pigeons behaved in accord with delay‐reduction models, whereas humans maximized overall rate of reinforcement. As discussed by Logue and associates in self‐control research, different types of reinforcement may affect sensitivity to delay differentially. Pigeons' responses were reinforced with food, a reinforcer that is consumable upon presentation. Humans' responses were reinforced with money, a reinforcer exchanged for consumable reinforcers after it was earned. Reinforcers that are immediately consumed may generate high sensitivity to delay and behavior described as delay reduction. Reinforcers with longer times to consumption may generate low sensitivity to delay and behavior that maximizes overall payoff.