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The contributions of Joseph V. Brady to behavioral pharmacology span more than 50 years and range from early studies using the Estes-Skinner (conditioned emotional response) procedure to examine drug effects and various physiological processes in experimental animals to the implementation of mobile methadone treatment services and to small group behavioral analyses in simulated space environments. This expansive range of activities is based on Brady's insight and innovative use of behavioral procedures, his spirited and unabashed enthusiasm for the discipline and its philosophical underpinnings, together with a collegiality and commitment to the experimental analysis of behavior that is both legendary and inspirational. These contributions are summarized and highlighted in this tribute that focuses primarily on Brady's contributions to behavioral pharmacology but which also acknowledges his conceptual and technical contributions spanning multiple disciplines.
PMCID: PMC2582211  PMID: 19070344
J.V. Brady; behavioral pharmacology; schedules of reinforcement; conditioned emotional response; experimental analysis of behavior; neuropsychopharmacology; neuroscience; behavioral physiology
Virtual organisms animated by a computational theory of selection by consequences responded on symmetrical and asymmetrical concurrent schedules of reinforcement. The theory instantiated Darwinian principles of selection, reproduction, and mutation such that a population of potential behaviors evolved under the selection pressure exerted by reinforcement from the environment. The virtual organisms' steady-state behavior was well described by the power function matching equation, and the parameters of the equation behaved in ways that were consistent with findings from experiments with live organisms. Together with previous research on single-alternative schedules (McDowell, 2004; McDowell & Caron, 2007) these results indicate that the equations of matching theory are emergent properties of the evolutionary dynamics of selection by consequences.
PMCID: PMC2582210  PMID: 19070343
selection by consequences; behavior dynamics; matching theory; computational modelling; concurrent schedules
Shull, Gaynor and Grimes advanced a model for interresponse time distribution using probabilistic cycling between a higher-rate and a lower-rate response process. Both response processes are assumed to be random in time with a constant rate. The cycling between the two processes is assumed to have a constant transition probability that is independent of bout length. This report develops an analytic form of the model which has a natural parametrization for a higher-rate within-bout responding and a lower-rate visit-initiation responding. The analytic form provides a convenient basis for both a nonlinear least-squares data reduction technique to estimate the model's parameters and Monte Carlo simulations of the model. In addition, the analytic formulation is extended to both a refractory period for the rats' behavior and, separately, the strongly-banded behavior seen with pigeons.
PMCID: PMC2582209  PMID: 19070342
IRT distributions; Monte Carlo simulation; pigeon IRT banding
The interresponse-time structures of pigeon key pecking were examined under variable-ratio, variable-interval, and variable-interval plus linear feedback schedules. Whereas the variable-ratio and variable-interval plus linear feedback schedules generally resulted in a distinct group of short interresponse times and a broad distribution of longer interresponse times, the variable-interval schedules generally showed a much more continuous distribution of interresponse times. The results were taken to indicate that a log survivor analysis or double exponential fit of interresponse times may not be universally applicable to the task of demonstrating that operant behavior can be dichotomized into bouts of engagement and periods of disengagement.
PMCID: PMC2582208  PMID: 19070341
interresponse time; variable-ratio; variable-interval; yoked schedules; Shull machine; key peck; pigeons
Previous research has shown that Lewis rats make more impulsive choices than Fischer 344 rats. Such strain-related differences in choice are important as they may provide an avenue for exploring genetic and neurochemical contributions to impulsive choice. The present systematic replication was designed to determine if these findings could be reproduced using a procedure less susceptible to within- or between-session carry-over effects that may have affected previous findings. Specifically, delays to the larger–later food reinforcer were manipulated between conditions following steady-state assessments of choice, and the order of delays across conditions was mixed. The results confirmed previous findings that Lewis rats made significantly more impulsive choices than Fischer 344 rats. Fischer 344 rats' preference for the larger–later reinforcer, on the other hand, was less extreme than reported in prior research, which may be due to carry-over effects inherent to the commonly used technique of systematically increasing delays within session. Previously reported across-strain motor differences were reproduced as Lewis rats had shorter latencies than Fischer 344 rats, although these latencies were not correlated with impulsive choice. Parallels between reduced dopamine function in Lewis rats and clinical reports of impulse-control disorders following treatment of Parkinson patients with selective D2/D3 dopamine agonists are discussed.
PMCID: PMC2582207  PMID: 19070340
Fischer 344 rats; Lewis rats; choice; impulsivity; delay-discounting; rat; lever press
The contribution of past experiences to concurrent resurgence was investigated in three experiments. In Experiment 1, resurgence was related to the length of reinforcement history as well as the reinforcement schedule that previously maintained responding. Specifically, more resurgence occurred when key pecks had been reinforced on a variable-interval 1-min schedule than a variable-interval 6-min schedule, but this effect may have been due either to the differential reinforcement rates or differential response rates under the two schedules. When reinforcement rates were similar (Experiment 2), there was more resurgence of high-rate than low-rate responding. When response rates were similar (Experiment 3), resurgence was not related systematically to prior reinforcement rates. Taken together, these three experimental tests of concurrent resurgence illustrate that prior response rates are better predictors of resurgence than are prior reinforcement rates.
PMCID: PMC2582206  PMID: 19070339
resurgence; behavioral history; response recovery; concurrent schedule; pigeons; key peck
The present experiment developed a methodology for assessing sensitivity of conditional-discrimination performance to within-session variation of reinforcer frequency. Four pigeons responded under a multiple schedule of matching-to-sample components in which the ratio of reinforcers for correct S1 and S2 responses was varied across components within session. Initially, five components, each arranging a different reinforcer-frequency ratio (from 1∶9 to 9∶1), were presented randomly within a session. Under this condition, sensitivity to reinforcer frequency was low. Sensitivity failed to improve after extended exposure to this condition, and under a condition in which only three reinforcer-frequency ratios were varied within session. In a later condition, three reinforcer-frequency ratios were varied within session, but the reinforcer-frequency ratio in effect was differentially signaled within each component. Under this condition, values of sensitivity were similar to those traditionally obtained when reinforcer-frequency ratios for correct responses are varied across conditions. The effects of signaled vs. unsignaled reinforcer-frequency ratios were replicated in two subsequent conditions. The present procedure could provide a practical alternative to parametric variation of reinforcer frequency across conditions and may be useful in characterizing the effects of a variety of manipulations on steady-state sensitivity to reinforcer frequency.
PMCID: PMC2582205  PMID: 19070338
conditional discrimination; sensitivity; within-session variation of reinforcer frequency; signaled reinforcer-frequency ratios; choice; key peck; pigeon
Four pigeons were exposed to a token-reinforcement procedure with stimulus lights serving as tokens. Responses on one key (the token-production key) produced tokens that could be exchanged for food during an exchange period. Exchange periods could be produced by satisfying a ratio requirement on a second key (the exchange-production key). The exchange-production key was available any time after one token had been produced, permitting up to 12 tokens to accumulate prior to exchange. Token accumulation, measured in terms of both frequency (percent cycles with accumulation) and magnitude (mean number of tokens accumulated), decreased as the token-production ratio increased from 1 to 10 across conditions (with exchange-production ratio held constant), and increased as the exchange-production ratio increased from 1 to 250 across conditions (with token-production ratio held constant). When tokens were removed, accumulation decreased markedly compared to conditions with tokens and the same schedules. These data show that token accumulation is an orderly function of token-production and exchange-production schedules, and they are broadly consistent with a unit-price model based on local and global responses per reinforcer.
PMCID: PMC2582204  PMID: 19070337
reinforcer accumulation; token reinforcement; unit price; fixed-ratio schedules; key peck; pigeons
Five experiments assessed associative symmetry in pigeons. In Experiments 1A, 1B and 2, pigeons learned two-alternative symbolic matching with identical sample- and comparison-response requirements and with matching stimuli appearing in all possible locations. Despite controlling for the nature of the functional stimuli and insuring all requisite discriminations, there was little or no evidence for symmetry. By contrast, Experiment 3 demonstrated symmetry in successive (go/no-go) matching, replicating the findings of Frank and Wasserman (2005). In view of these results, I propose that in successive matching, (1) the functional stimuli are stimulus–temporal location compounds, (2) continual nonreinforcement of some sample–comparison combinations juxtaposed with reinforcement of other combinations throughout training facilitates stimulus class formation, (3) classes consist of the elements of the reinforced combinations, and (4) common elements produce class merger. The theory predicts that particular sets of training relations should yield “antisymmetry”: Pigeons should respond more to a reversal of the nonreinforced symbolic baseline relations than to a reversal of the reinforced relations. Experiment 4 confirmed this counterintuitive prediction. These results and other theoretical implications support the idea that equivalence relations are a natural consequence of reinforcement contingencies.
PMCID: PMC2582203  PMID: 19070336
associative symmetry; antisymmetry; stimulus classes; equivalence relations; successive matching; pigeons; key peck
10.  Relative Reinforcer Rates and Magnitudes Do Not Control Concurrent Choice Independently 
One assumption of the matching approach to choice is that different independent variables control choice independently of each other. We tested this assumption for reinforcer rate and magnitude in an extensive parametric experiment. Five pigeons responded for food reinforcement on switching-key concurrent variable-interval variable-interval schedules. Across conditions, the ratios of reinforcer rates and of reinforcer magnitudes on the two alternatives were both manipulated. Control by each independent variable, as measured by generalized-matching sensitivity, changed significantly with the ratio of the other independent variable. Analyses taking the model-comparison approach, which weighs improvement in goodness-of-fit against increasing number of free parameters, were inconclusive. These analyses compared a model assuming constant sensitivity to magnitude across all reinforcer-rate ratios with two alternative models. One of those alternatives allowed sensitivity to magnitude to vary freely across reinforcer-rate ratios, and was less efficient than the common-sensitivity model for all pigeons, according to the Schwarz-Bayes information criterion. The second alternative model constrained sensitivity to magnitude to be equal for pairs of reinforcer-rate ratios that deviated from unity by proportionately equal amounts but in opposite directions. This model was more efficient than the common-magnitude-sensitivity model for 2 of the pigeons, but not for the other 3. An analysis of variance, carried out independently of the generalized-matching analysis, also showed a significant interaction between the effects of reinforcer rate and reinforcer magnitude on choice. On balance, these results suggest that the assumption of independence inherent in the matching approach cannot be maintained. Relative reinforcer rates and magnitudes do not control choice independently.
PMCID: PMC2531519  PMID: 18831124
choice; concurrent schedules; generalized matching; reinforcer rate; reinforcer magnitude; key peck; pigeons
11.  The Second Victor G. Laties Award 
PMCID: PMC2529192
12.  An Inexpensive Infrared Detector to Verify The Delivery of Food Pellets 
The reproducibility of experimental outcomes depends on consistent control of independent variables. In food-maintained operant performance, it is of utmost importance that the quantity of food delivered is reliable. To that end, some commercial food pellet dispensers have add-on attachments to sense the delivery of pellets. Not all companies, however, offer such add-ons. Aside from availability, cost and temporary reduction in throughput may be a problem for smaller labs. The present paper outlines our recent development of a simple, inexpensive infrared device to detect and confirm the delivery of pellets. The in-line construction of the detector routes the falling pellet through a barrel so that it passes between an infrared emitter and receiver. The circuitry was designed to be compatible with all commercially available behavioral measurement systems, and so may be retrofit to any existing system. Our tests with the detector so far have shown that it is 100% accurate in detecting pellet delivery. The individual unit cost is approximately 25 dollars. The low cost and versatility of the device offer an easy method to ensure the integrity of food delivery in operant settings.
PMCID: PMC2529191  PMID: 18831128
pellet; detection; infrared; reliability
13.  Individual Differences, Intelligence, and Behavior Analysis 
Despite its avowed goal of understanding individual behavior, the field of behavior analysis has largely ignored the determinants of consistent differences in level of performance among individuals. The present article discusses major findings in the study of individual differences in intelligence from the conceptual framework of a functional analysis of behavior. In addition to general intelligence, we discuss three other major aspects of behavior in which individuals differ: speed of processing, working memory, and the learning of three-term contingencies. Despite recent progress in our understanding of the relations among these aspects of behavior, numerous issues remain unresolved. Researchers need to determine which learning tasks predict individual differences in intelligence and which do not, and then identify the specific characteristics of these tasks that make such prediction possible.
PMCID: PMC2529190  PMID: 18831127
intelligence; learning; three-term contingency; individual differences; processing speed; working memory; humans
14.  The First Victor G. Laties Award 
PMCID: PMC2529189
15.  An Invitation to Behavior Analysts: Review of in Search of Memory: The Emergence of A New Science of Mind by Eric R. Kandel 
This fascinating autobiography and multifaceted case history in neuroscience research is accessible to laymen and potentially instructive to working scientists. Kandel takes the reader through his thought processes as he describes experiments that led to some of the past decades' major neuroscience discoveries (some highlights of which are summarized in the review's Appendix), and eventually to his Nobel Prize. The review analyzes some of the terminological and conceptual issues that have often inhibited communication between behavior analysts and neuroscientists, with special attention to some of Bennett and Hacker's admonitions viewed from the perspective of language evolution and linguistics. The review then discusses opportunities for behavior analysts to collaborate with neuroscientists by applying behavioral contingency analysis to help specify the independent variables of neuroscience experiments described by Kandel. Finally, it examines Kandel's provocative heuristics for locating important research problems, and the lessons that can be gleaned from the book regarding the attributes of potentially great achievers.
PMCID: PMC2529188
cognitive neuroscience; contingencies; scientific behavior; scientific method; terminology; the mereological fallacy; reductionism
16.  The Reinforcing Effects of Houselight Illumination During Chained Schedules of Food Presentation 
Pigeons' keypecking was maintained under two- and three-component chained schedules of food presentation. The component schedules were all fixed-interval schedules of either 1- or 2-min duration. Across conditions the presence of houselight illumination within each component schedule was manipulated. For each pigeon, first-component response rates increased significantly when the houselight was extinguished in the first component and illuminated in the second. The results suggest that the increase was not the result of disinhibition or modification of stimulus control by component stimuli, but appears to result from the reinforcement of responding by the onset of illumination in the second component. Additionally, the apparent reinforcing properties of houselight illumination resulted neither from association of the houselight with the terminal component of the chained schedule nor through generalization of the hopper illumination present during food presentation. The results of the present series of experiments are related to previous demonstrations of illumination-reinforced responding and to the interpretation of data from experiments employing houselight illumination as stimuli associated with timeout or brief stimuli in second-order schedules.
PMCID: PMC2529187  PMID: 18831125
houselight illumination as primary reinforcer; chained FI schedules; pigeons
17.  E. B. Holt on Teleological Behaviorism 
PMCID: PMC2529186
18.  Formation of Partially and Fully Elaborated Generalized Equivalence Classes 
Most complex categories observed in real-world settings consist of perceptually disparate stimuli, such as a picture of a person's face, the person's name as written, and the same name as heard, as well as dimensional variants of some or all of these stimuli. The stimuli function as members of a single partially or fully elaborated generalized equivalence class when they occasion the mutual selection of each other after the establishment of some subset of relations among the stimuli. Indeed, it is these generalized relations among stimuli that enable an individual to respond appropriately to the inevitable flux of natural environments. The present experiments involved procedures for producing both types of generalized equivalence class and for evaluating their retention. Granting the formal and functional similarities that exist between generalized equivalence classes and natural categories, natural kinds, and fuzzy superordinate classes, the variables responsible for the emergence of the former might also account for the emergence of the latter three phenomena. In Experiment 1, After forming an A′–B′ class, a B′–C relation was trained and generalization tests were conducted with B′–C, C–B′, A′–C, and C′–A. Two of 5 participants passed the tests documenting the formation of A′–B′–C classes. Failures occurred in the A′–C and C–A′ tests but not the B′–C and C–B′ tests. Failures were also correlated with time between A′–B′ class formation and C-based testing and with the absence of baseline confirmation when training and testing were separated by about one week. Experiment 2 replicated Experiment 1 but presented baseline confirmation probes immediatley prior to testing when training and testing were separated by one week; all participants then formed partially elaborated generalized equivalence classes. In Experiment 3, 5 of 6 participants formed fully elaborated generalized equivalence classes, represented as A′ = B′ = C′ .
PMCID: PMC2529185  PMID: 18831123
partially elaborated generalized equivalence class; fully elaborated generalized equivalence class; linked perceptual class; computer keyboard as response device; conditional discrimination; college students
19.  J. Michael Harrison (1915–2007): A Research Career Well Lived 
PMCID: PMC2529184  PMID: 18831122
J.M. Harrison; stimulus control; audition; sound localization; auditory anatomy; evolution; learning
20.  Tolerance to Effects of Cocaine on Behavior Under A Response-Initiated Fixed-Interval Schedule 
Tolerance to effects of cocaine can be modulated by schedules of reinforcement. With multiple ratio schedules, research has shown an inverse relationship between ratio requirement and amount of tolerance that resulted from daily administration of the drug. In contrast, tolerance to the effects of cocaine on behavior under multiple interval schedules generally has developed regardless of interval value. Under interval schedules reinforcement depends on the animal making one response following a time interval. Thus, as time to respond increases, the time to reinforcement decreases. On the other hand, fixed ratio schedules require a specified number of responses to be made prior to reinforcement. Therefore, delaying the initiation of responding does not coincide with a significant decrease in the time to reinforcement. In the current experiment, 6 pigeons were trained to respond under a three-component multiple schedule, with a different tandem fixed-ratio 1 fixed-interval schedule in each component. The multiple schedule required one response, which was followed by one of three fixed-interval values (5, 15, or 60 s). Thus, the multiple schedule was interval-like because after the fixed-ratio 1, only one more response was required for reinforcement, but it was also ratio-like because the length of the pause at the beginning of each interreinforcer interval affected the time until the next reinforcer. Acute administration of cocaine generally resulted in dose-dependent decreases in responding. Chronic (i.e., daily) administration of a rate-decreasing dose resulted in tolerance patterns similar to those usually obtained with multiple ratio schedules. That is, the magnitude of tolerance was related inversely to schedule size. These results suggest that delay to reinforcement from the initial response may play a role in the development of schedule-parameter-related tolerance.
PMCID: PMC2529183  PMID: 18831126
cocaine; tolerance; fixed-interval schedules; fixed-ratio schedules; tandem schedules; key peck; pigeons
21.  An Inexpensive and Automated Method for Presenting Olfactory or Tactile Stimuli to Rats in a Two-Choice Discrimination Task 
An inexpensive and automated method for presentation of olfactory or tactile stimuli in a two-choice task for rats was implemented with the use of a computer-controlled bidirectional motor. The motor rotated a disk that presented two stimuli of different texture for tactile discrimination, or different odor for olfactory discrimination. Because the solid olfactory stimuli were placed outside the chamber in metal pods with a mesh at front for odor sampling, “washout” of odors between trials was not necessary. To avoid differential auditory cues from motor rotation, the stimuli were arranged such that on each trial the motor always rotated exactly one quarter revolution (in 1 s), left or right, to present the next stimulus at trial start. To illustrate the use of the equipment, 2 rats were trained on tactile discrimination and 2 rats on olfactory discrimination. The rats sampled the stimulus on the disk through a port on the back wall by sniffing at it (olfactory) or touching it (tactile). The task was a go-left/go-right discrimination with the stimulus on the disk being discriminative for which lever provided reinforcement. The rats reached a stable level above 90% correct after 21 and 32 training sessions for tactile and olfactory discrimination, respectively. The article outlines how the equipment was constructed from low-cost components. Inputs from and outputs to the equipment were implemented through the parallel port of a personal computer without the use of a commercial interface board. The method of automated and low-cost presentation of olfactory or tactile stimuli should be of use for a variety of experimental situations such as matching-to-sample and cross-modal discrimination.
PMCID: PMC2442869  PMID: 18683616
olfactory discrimination; tactile discrimination; two-choice task; automated stimulus presentation; bidirectional motor; rats
22.  Common Control by Compound Samples in Conditional Discriminations 
We tested whether teaching control by single stimulus samples in conditional discriminations would result in common control of two-stimuli compound samples, and vice versa. In Experiment 1, 5 participants were first taught four single-sample conditional discriminations. The first conditional discrimination was as follows: given sample stimulus P1, select comparison stimulus A1 and not A2; given sample P2 select comparison A2 and not A1. The second conditional discrimination was as follows: given sample P1 select comparison B1 and not B2; given sample P2 select B2 and not B1. Different sample stimuli (Q1 and Q2) were used in the third and fourth conditional discriminations. Moreover, A1 and B1 were presented together as comparisons, such that, if Q1 was presented as the sample, A1 was correct and B1 was incorrect; and if Q2 was presented as the sample, B1 was correct and A1 was incorrect. A2 and B2 were also presented as comparisons. When Q1 was presented, A2 was correct and when Q2 was presented B2 was correct. After training with these four single stimulus sample discriminations, participants were tested with compound PQ samples presented with A1, A2, B1, and B2 as comparisons. If common control were established by the PQ stimuli, a participant would select A1 when P1Q1 was presented, A2 when P2Q1 was presented, B1 when P1Q2 was presented, and B2 when P2Q2 was presented. Such common control by PQ samples occurred in 4 of 5 participants. In Experiment 2, 4 participants were given reverse training. They were first taught to select the A1, A2, B1, and B2 stimuli in response to the appropriate PQ combinations and then probed on the single stimulus sample discriminations. All 4 participants were successful on this probe. Experiments 3 and 4 investigated the effects of teaching additional conditional discriminations with novel stimuli on subsequent transfer from the single-sample discriminations to performance on the compound-sample conditional discrimination.
PMCID: PMC2441582  PMID: 18683614
restricted control; conditional discriminations; compound-samples; emergent relations; stimulus equivalence; adults
23.  On the Origins of Emergent Differential Sample Behavior 
Two experiments evaluated the source(s) of emergent differential sample behavior in pigeons. Initially, pigeons learned two-sample, two-alternative symbolic matching in which different patterns of sample responding were required to produce the comparisons. Afterwards, two other samples nominally identical to the comparisons were added to the matching task. On new-sample trials, completion of either sample–response requirement produced comparison alternatives which were either the same as or different from the alternatives on the familiar-sample trials. Differential responding to the new samples developed only when the comparisons were the same as the familiar samples. The results are consistent with acquired sample equivalence and adventitious reinforcement accounts of emergent sample behavior and are inconsistent with bidirectional transfer (symmetry) between the response patterns explicitly required to the originally trained (familiar) samples and the subsequently reinforced comparisons.
PMCID: PMC2441581  PMID: 18683613
emergent sample behavior; differential sample responding; bidirectional transfer; symmetry; acquired equivalence; adventitious reinforcement; pigeons; pecking
24.  Visual Reinforcement in the Female Siamese Fighting Fish, Betta Splendens 
Operant conditioning with Betta splendens (Bettas) has been investigated extensively using males of the species. Ethological studies of female Bettas have revealed aggressive interactions that qualitatively parallel those between male Bettas. Given these similarities, four experiments were conducted with female Bettas to examine the generality of a widely reported finding with males: mirror-image reinforcement. Swimming through a ring was reinforced by a 10–s mirror presentation. As with males, ring swimming was acquired and maintained when mirror presentations were immediate (Experiments 1, 2, and 3) and delayed (Experiment 4). The failure of conventional extinction (Experiments 1 and 2) and response-independent mirror presentations (Experiment 3) to maintain responding confirmed the reinforcing properties of mirror presentation. These results extend previous findings of mirror images as reinforcers in males of the same species and illustrate a complementarity between behavioral ecology and the experimental analysis of behavior.
PMCID: PMC2441580  PMID: 18683612
mirror-image reinforcement; extinction; response-independent mirror presentation; aggression; ring swimming; female Betta splendens
25.  Context Effects in a Temporal Discrimination Task: Further Tests of the Scalar Expectancy Theory and Learning-to-Time Models 
Pigeons were trained on two temporal bisection tasks, which alternated every two sessions. In the first task, they learned to choose a red key after a 1-s signal and a green key after a 4-s signal; in the second task, they learned to choose a blue key after a 4-s signal and a yellow key after a 16-s signal. Then the pigeons were exposed to a series of test trials in order to contrast two timing models, Learning-to-Time (LeT) and Scalar Expectancy Theory (SET). The models made substantially different predictions particularly for the test trials in which the sample duration ranged from 1 s to 16 s and the choice keys were Green and Blue, the keys associated with the same 4-s samples: LeT predicted that preference for Green should increase with sample duration, a context effect, but SET predicted that preference for Green should not vary with sample duration. The results were consistent with LeT. The present study adds to the literature the finding that the context effect occurs even when the two basic discriminations are never combined in the same session.
PMCID: PMC2441579  PMID: 18683611
bisection procedure; context effect; temporal discrimination; timing models; key peck; pigeon

Results 1-25 (3959)