bluuebunny/crossref_metadata_2025 huggingface dataset:
FEEDBACK EFFECTS ON SEQUENTIAL ORDERING IN HUMANS
Authors: Deitz Samuel M. , Gaydos Gerard R. , Lawrence Andrea D. , Quinn Patrick C. , Brasher Lynda D. , Fredrick Laura D.
Published: March 2006

Under various feedback conditions, 38 college undergraduates were asked to rearrange abstract graphic characters on a computer screen, placing them in arbitrarily designated “correct” sequences. Two sets of seven horizontally arrayed stimuli were used. In Experiment 1, subjects in Group 1 learned to arrange the first set under Selection Feedback in which a “+” appeared above each character after it was selected in the correct order and to arrange the second set under Order Feedback in which a correct response produced a copy of the character in its correct ordinal position at the top of the screen. For Group 2 the order of these conditions was reversed. In Experiment 2, for subjects in Group 3, correct responses produced neither of these types of feedback. Subjects in Group 4 received Order Feedback only until the first set was correctly ordered once. Order Feedback was more effective than Selection Feedback during initial acquisition of the first set but not during maintenance; no differences were found for the second set. Only 2 of 9 subjects successfully put the characters in correct sequential order under the No Feedback condition. When, in Experiment 2, Order Feedback was eliminated after the first correctly arranged sequence, the steady‐state criteria were met more slowly than in Experiment 1.
INCOME AND CHOICE BETWEEN DIFFERENT GOODS
Authors: Shurtleff David , Warren‐Boulton Frederick R. , Silberberg Alan
Published: March 2006

In Experiment 1, 3 rats chose between two simultaneously operating variable‐interval schedules, one of which provided saccharin water and the other, food. In five conditions, the absolute (and equal) reinforcement rates provided by the pair of equal‐valued schedules were manipulated in the range of 36 to 240 per hour. Experiment 2 was identical to Experiment 1 except that these schedules operated successively, arranged by requiring the rat to stand on the side of the chamber correlated with each schedule. Food/saccharin choice ratios were inversely related to reinforcement rate in both experiments, although this effect was stronger in Experiment 2. When delivery rates were high, preference for food over saccharin often reversed as the session progressed. The results were interpretable in terms of economic accounts of choice (e.g., the minimum‐needs hypothesis), as well as in terms of traditional psychological accounts (e.g., matching theory).
THE STRUCTURE OF EQUIVALENCE CLASSES
Authors: Fields Lanny , Verhave Thom
Published: March 2006

The structure of equivalence classes can be completely described by four parameters: class size, number of nodes, the distribution of “singles” among nodes, and directionality of training. Class size refers to the number of stimuli in a class. Nodes are stimuli linked by training to at least two other stimuli. Singles are stimuli linked by training to only one other stimulus. The distribution of singles refers to the number of singles linked by training to each node. Directionality of training refers to the use of stimuli as samples and as comparison stimuli in training. These four parameters define the different ways in which the stimuli in a class can be organized, and thus provide a basis for systematically characterizing the properties of stimuli in a given equivalence class. The four parameters can also be used to account for the development of individual differences that are commonly characterized in terms of “understanding” and connotative meaning.

Methods are described for generating all possible combinations of parameter values, and a formula is introduced which specifies all of the parameter values for an equivalence class. Its utility for interrelating experimental procedures is demonstrated by analyzing a number of representative experiments that have addressed equivalence‐class formation.
RESPONSE‐REINFORCER RELATIONS AND THE MAINTENANCE OF BEHAVIOR
Authors: Gleeson Suzanne , Lattal Kennon A.
Published: March 2006

The effects on pigeons' key pecking of unsignaled delays of reinforcement and response‐independent reinforcement were compared after either variable‐interval or differential‐reinforcement‐of‐low‐rate baseline schedules. One 30‐min session arranging delayed reinforcement and one 30‐min session arranging response‐independent reinforcement were conducted daily, 6 hr apart. A within‐subject yoked‐control procedure equated reinforcer frequency and distribution across the two sessions. Response rates usually were reduced more by response‐independent than by delayed but response‐contingent delivery of reinforcers. Under both schedules, response rates were lower when obtained delays were greater. These results bear upon methodological and conceptual issues regarding comparisons of contingencies that change the temporal response—reinforcer relations.
A ROLE FOR NEGATIVE REINFORCEMENT OF RESPONSE OMISSION IN PUNISHMENT?
Authors: Arbuckle Jeffery L. , Lattal Kennon A.
Published: March 2006

This experiment attempted to disentangle response‐rate reductions controlled by the direct suppressive effects of a punisher from those due to negative reinforcement of response omission. Key‐peck responding of pigeons was maintained by a conjoint variable‐interval 3‐min schedule of food presentation variable‐interval 30‐s schedule of response‐dependent electric shock presentation. Omission of responses for 5, 10, or 30 s resulted in the possibility of canceling a scheduled shock. Response rates were a function of required pause duration, with lower rates occurring when longer periods of response omission were required for shock cancellation. These results show that, with several parameters of punishment held constant, response rates were controlled by the negative reinforcement contingency. Such a finding argues for renewed consideration of the role of negative reinforcement in punishment contingencies.
PUNISHMENT OF SCHEDULE‐INDUCED DRINKING IN RATS BY SIGNALED AND UNSIGNALED DELAYS IN FOOD PRESENTATION
Authors: Pellon Ricardo , Blackman Derek E.
Published: March 2006

Food‐deprived rats were exposed to a fixed‐time 60‐s schedule of food‐pellet presentation and developed schedule‐induced drinking. Using an ABA reversal design, three experiments investigated the effects of events then made dependent on licks. In Experiment 1, lick‐dependent signaled delays (10 s) in food presentation in general led to decreased drinking, which recovered when the signaled delays were discontinued. The drinking of yoked‐control rats, which received food at the same times as those exposed to the signaled‐delay contingency, showed much smaller changes. Experiment 2 showed that 10‐s lick‐dependent signals alone did not reduce drinking. In Experiment 3, when licks produced unsignaled 10‐s delays in food there were less marked and more gradual changes in drinking than in Experiment 1, although these effects again were greater than with yoked‐control animals. We concluded that both signaled and unsignaled delays functioned as punishers of drinking. These findings support the view that schedule‐induced drinking, like operant behavior, is subject to control by its consequences.
STIMULUS‐ AND PELLET‐INDUCED DRINKING DURING A SUCCESSIVE DISCRIMINATION
Authors: Minor Thomas R.
Published: March 2006

In three experiments, interim water drinking was examined in rats exposed to a multiple schedule whose two components were extinction and a variable‐time 30‐s schedule of food delivery. Two different drinking patterns were observed in Experiment 1. Pellet‐induced drinking, characterized by high rates of postpellet drinking in the variable‐time component, with little or no drinking in extinction, occurred when the acquisition of stable postpellet drinking preceded discrimination training. Stimulus‐induced drinking, characterized by a burst of drinking at the onset of extinction, with no drinking during the variable‐time schedule, occurred when discrimination training preceded all other experimental conditions. With extended training, stimulus‐induced drinking eventually was accompanied by postpellet drinking. In Experiment 2, the rate of stimulus‐induced drinking and the number of sessions during which it occurred without postpellet drinking were found to be inversely related to component duration. In Experiment 3, the rate of schedule‐induced drinking was found to vary directly with component duration.
AUDITORY DISCRIMINATION: THE KONORSKI QUALITY‐LOCATION EFFECT
Authors: Neill John C. , Harrison J. M.
Published: March 2006

Konorski showed that when a go/no‐go procedure was used, sound quality discriminations were rapidly acquired and sound location discriminations were slowly acquired. These findings have been interpreted as a general constraint on the acquisition of auditory discriminations (quality‐location effect). However, experiments carried out within an evolutionary framework (Harrison, 1984) have shown that the rate of acquisition of sound location discriminations varies widely as a function of the inclusion or exclusion of naturalistic features. These data suggest that Konorski's findings were a function of the special conditions of the experiments. The first purpose of the present experiments was to assess whether rats showed the effects noted by Konorski when studied under similar conditions. The second purpose was to study the effect of manipulating two natural features (novelty and stimulus‐response adjacency) to assess whether the acquisition rates of quality and location discriminations could be greatly modified or made approximately equal, or both. When a go/no‐go procedure was used and the other conditions were similar to those of Konorski, rats acquired a quality discrimination but did not acquire a location discrimination. However, when the S+ or S‐ were presented through a closely adjacent speaker, the sound location discrimination was acquired as rapidly as the quality discrimination. Finally, preexposing the animal to either S+ or S‐ retarded the rate of or prevented the acquisition of the quality discrimination. The experiments showed that the quality‐location effect was determined primarily by the conditions used in Konorski's experiments, and that the effect is not a general constraint on learning.
THE INTERACTION OF STIMULUS AND REINFORCER CONTROL IN COMPLEX TEMPORAL DISCRIMINATION
Authors: Davison Michael , McCarthy Dianne
Published: March 2006

Six pigeons were trained in a discrete‐trials signal‐detection procedure to discriminate between a fixed‐duration stimulus (5 s or 20 s) and a set of variable durations ranging from 2.5 s to 57.5 s in steps of 5 s. For each fixed‐duration stimulus, the ratio of reinforcer frequencies contingent upon reporting the fixed versus the variable stimulus was systematically manipulated. Detection performance was well controlled by both the stimulus value and the reinforcer ratio. Both the discriminability between the fixed duration and the set of variable durations, and the discriminability between the fixed duration and each of the variable durations, were independent of the reinforcer‐frequency ratio when discriminability was measured as log d. The sensitivity of response bias to reinforcement‐ratio changes was independent of the value of the fixed duration, but was not independent of the discriminability of the variable durations from the fixed durations. Under current models, discriminability measures in complex temporal discrimination may be independent of biasing manipulations, but bias measures are not independent of stimulus values.
THE LINEAR SYSTEM THEORY'S ACCOUNT OF BEHAVIOR MAINTAINED BY VARIABLE‐RATIO SCHEDULES
Authors: McDowell J. J , Wixted John T.
Published: March 2006

The mathematical theory of linear systems, which has been used successfully to describe behavior maintained by variable‐interval schedules, is extended to describe behavior maintained by variable‐ratio schedules. The result of the analysis is a pair of equations, one of which expresses response rate on a variable‐ratio schedule as a function of the mean ratio requirement () that the schedule arranges. The other equation expresses response rate on a variable‐ratio schedule as a function of reinforcement rate. Both equations accurately describe existing data from variable‐ratio schedules. The theory accounts for two additional characteristics of behavior maintained by variable‐ratio schedules; namely, the appearance of strained, two‐valued (i.e., zero or very rapid) responding at large s, and the abrupt cessation of responding at a boundary . The theory also accounts for differences between behavior on variable‐interval and variable‐ratio schedules, including (a) the occurrence of strained responding on variable‐ratio but not on variable‐interval schedules, (b) the abrupt cessation of responding on variable‐ratio but not on variable‐interval schedules even at extreme parameter values, and (c) the occurrence of higher response rates on variable‐ratio than on variable‐interval schedules. Furthermore, given data from a series of variable‐interval schedules and from a series of concurrent variable‐ratio variable‐interval schedules, the theory permits quantitative prediction of many properties of behavior on single‐alternative variable‐ratio schedules. The linear system theory's combined account of behavior on variable‐interval and variable‐ratio schedules is superior to existing versions of six other mathematical theories of variable‐interval and variable‐ratio responding.
SELF‐CONTROL IN MENTALLY RETARDED ADOLESCENTS: CHOICE AS A FUNCTION OF AMOUNT AND DELAY OF REINFORCEMENT
Authors: Ragotzy Steven P. , Blakely Elbert , Poling Alan
Published: March 2006

Three severely mentally retarded adolescents were studied under discrete‐trial procedures in which a choice was arranged between edible reinforcers that differed in magnitude and, in some conditions, delay. In the absence of delays the larger reinforcer was consistently chosen. Under conditions in which the smaller reinforcer was not delayed, increasing the delay to delivery of the larger reinforcer decreased the percentage of trials in which that reinforcer was chosen. All subjects directed the majority of choice responses to the smaller reinforcer when the larger reinforcer was sufficiently delayed, although the value at which this occurred differed across subjects. Under conditions in which the larger reinforcer initially was sufficiently delayed to result in preference for the smaller one, progressively increasing in 5‐s increments the delay to both reinforcers increased percentage of trials with the larger reinforcer chosen. At sufficiently long delays, 2 of the subjects consistently chose the larger, but more delayed, reinforcer, and the 3rd subject chose that reinforcer on half of the trials. These results are consistent with the findings of prior studies in which adult humans responded to terminate noise and pigeons responded to produce food.
EFFECTS OF SCOPOLAMINE ON REPEATED ACQUISITION OF RADIAL‐ARM MAZE PERFORMANCE BY RATS
Authors: Peele David B. , Baron Scott P.
Published: March 2006

Rats repeatedly acquired the performance of selecting only the four baited arms in an automated eight‐arm radial maze, with the arms containing food pellets randomly assigned prior to each session. During each 14‐trial (trial: obtain all four pellets) daily session, the number of errors (selecting nonbaited arms or repeating arm selections) showed a within‐session decline, and choice accuracy for the first four arm selections showed a positive acceleration across trials for all rats. An index‐of‐curvature statistic, calculated for total errors, was used to quantify both the within‐ and between‐session improvement of performance. Scopolamine (0.03 to 0.3 mg/kg, ip), but not methylscopolamine (0.3 mg/kg), reduced the accuracy of the first four selections of each trial and increased total within‐session errors for all rats. Session times also were increased by scopolamine. An examination of within‐session accuracy showed only slight signs of improvement at the higher dosages of scopolamine. The results indicate that behavior in transition states maintained by reinforcement contingencies in the radial maze is similar to that maintained by extended chained schedules, despite the fact that some of the stimuli controlling behavior in the maze are absent at the moment behavior is emitted.
CHOICE IN TRANSITION: A COMPARISON OF MELIORATION AND THE KINETIC MODEL
Authors: Myerson Joel , Hale Sandra
Published: March 2006

Transition‐state choice behavior of pigeons was examined in two experiments designed to test predictions of melioration and the kinetic model. Both experiments began with an initial training condition during which subjects were maintained on concurrent variable‐interval schedules. In Experiment 1, subjects were then exposed to concurrent variable‐ratio schedules, whereas in Experiment 2, subjects were then exposed to concurrent extinction. Contrary to the predictions of melioration, but consistent with the kinetic model, acquisition of preference on concurrent variable‐ratio schedules followed a negatively accelerated logistic trajectory, and preference remained stable in concurrent extinction. Predictions made by the kinetic model concerning rates of switching between alternatives were also supported.
CUNCURRENT SCHEDULES: INTERACTION OF REINFORCER FREQUENCY AND REINFORCER DURATION
Authors: Davison Michael
Published: March 2006

Six pigeons were trained on concurrent variable‐interval schedules with unequal reinforcer durations for the two responses. The schedules arranged on the two keys were kept equal while they were varied in absolute size. As the overall reinforcer rate was increased, both response‐allocation and time‐allocation measures of choice showed a trend toward indifference, and measures of sensitivity to reinforcer‐duration ratios significantly decreased. Recent reports have shown that the generalized matching law cannot describe the changes in behavior allocation under constant delay‐, duration‐, or rate‐ratios when changes are made in the absolute levels of each of these variables. The present results complement these findings by demonstrating that the concatenated generalized matching law cannot describe the interactions of two reinforcer variables on behavior allocation.
ESTIMATION OF INDIFFERENCE POINTS WITH AN ADJUSTING‐DELAY PROCEDURE
Authors: Mazur James E.
Published: March 2006

In a series of conditions, pigeons chose between 1.5 s and 3 s of access to grain, each preceded by some delay. The delay that preceded the small reinforcer was constant throughout a condition. The delay that preceded the large reinforcer was increased or decreased a number of times each session in order to estimate an “indifference point,” a delay at which the subject chose each alternative about equally often. The experiment was designed to determine whether variations in any of four features of this adjusting‐delay procedure would systematically alter the estimated indifference points. The four features were the total trial duration, the number of center‐key responses necessary to begin a trial, the number of choice trials that preceded each change in the adjusting delay, and step size—the size of each increment and decrement in the delay. Manipulation of the first three features had no systematic effects on the indifference points. As step size was increased from 0.5 s to 6 s, within‐session variability of the adjusting delay steadily increased, and the 6‐s step size produced larger indifference‐point estimates for some subjects. The results suggest that, within certain limits, these procedural features can be altered without affecting the indifference‐point estimates, but that the use of a large step size can distort the estimates. Some theoretical implications of the relative constancy of indifference points across these procedural variations are discussed.
PREFERENCE FOR SIMPLE INTERVAL SCHEDULES OF REINFORCEMENT IN CONCURRENT CHAINS: EFFECTS OF SEGMENTATION RATIO
Authors: Leung Jin‐Pang , Winton Alan S. W.
Published: March 2006

A concurrent‐chains procedure was used to examine pigeons' preferences between segmented and unsegmented terminal‐link schedules of reinforcement. During the initial link, a pair of independent, concurrent variable‐interval 60‐s schedules was in effect. In the terminal link, reinforcement was provided by a chain fixed‐interval fixed‐interval schedule on one key and by a simple fixed‐interval schedule with an equal interreinforcement interval in the other. The relative duration between the first and second components (segmentation ratio) in the terminal‐link chained schedule was systematically varied while the terminal‐link duration was kept constant at either 15 s or 30 s in two sets of conditions. With few exceptions, the simple schedule was preferred to the chained schedule. Furthermore, this preference was inversely related to the size of the segmentation ratio in the segmented schedule. When the segmentation ratio was smaller than 1:1, preference was more extreme for a 30‐s condition than for a 15‐s condition. However, preference decreased more rapidly in conditions with the longer terminal‐link duration when the ratio increased. Taken together, these results were consistent with previous findings concerning the effect of the terminal‐link duration on choice between segmented and unsegmented schedules. In addition, the data suggested that segmentation ratio in a segmented schedule constitutes another potent factor influencing preference for the unsegmented schedule.
ESTABLISHING AUDITORY STIMULUS CONTROL OVER AN EIGHT‐MEMBER EQUIVALENCE CLASS VIA CONDITIONAL DISCRIMINATION PROCEDURES
Authors: Saunders Richard R. , Wachter Judith , Spradlin Joseph E.
Published: March 2006

Two eight‐member equivalence classes of visual stimuli were established during three phases of a training program. In Phase 1, two training arrangements were compared. In one, 3 subjects were taught on different trials to select from a single pair of comparison stimuli (A1, A2) in response to eight sample stimuli that were trained in pairs (B1, B2; C1, C2; D1, D2; E1, E2). In the second arrangement, subjects were taught to select from four pairs of comparisons (B1, B2; C1, C2; D3, D2; E2, E2) in response to two samples (A1) A2). Training with the single pair of comparison stimuli resulted in the development of equivalence relations (B1C1, B2C2, D1B1, D2B2, B1E1, B2E2, C1D1, C2D2, C1E1, C2E2, D1E1, D2E2, and their reciprocals) between the sample stimuli without direct training of these relations. In the other training arrangement, these relations among the comparison stimuli developed in the performance of 1 subject only. In Phase 2, three new pairs of stimuli (F1, F2; G1, G2; H1, H2) were substituted for three of the original pairs (B1, B2; C1, C2; D1, D2) and the training arrangements for the groups were reversed. Following training, the performances that showed equivalence relations on the probes in the first phase also showed equivalence relations in the second phase. If such relations did not develop in the first phase, they did not do so in the second phase. In Phase 3, relations between stimuli across the two previous phases (e.g., B1F1, B2F2, B1G1, B2H2, C1F1, etc.) were investigated. The 4 subjects whose performances showed the development of these relations were taught to select one stimulus from each class (E1 and E2) in response to a verbal label (I1 and I2) and then were tested to see if the verbal label controlled responding to the remaining members of the class (e.g., I1A1, I2A2, I1B1, I2B2, etc.). For 3 subjects, this generalized control occurred; for the 4th, generalization occurred only after verbal training with a second pair of visual stimuli (F1 and F2). In retests several months later, these auditory‐visual relations were found to be intact or, if not, were recovered without direct training.
EMERGENT SIMPLE DISCRIMINATION ESTABLISHED BY INDIRECT RELATION TO DIFFERENTIAL CONSEQUENCES
Authors: Rose Julio C. de , McIlvane William J. , Dube William V. , Galpin Virginia C. , Stoddard Lawrence T.
Published: March 2006

Three experiments examined a discrimination training sequence that led to emergent simple discrimination in human subjects. The experiments differed primarily in their subject populations. Normally capable adults served in the first experiment, preschool children in the second, and mentally retarded adults in the third. In all experiments, subjects learned a simple simultaneous discrimination: When visual stimuli A1 and A2 were displayed together, reinforcers followed selections of A1, the S+, but not A2, the S‐. The subjects also learned a conditional discrimination taught with an arbitrary visual‐visual matching‐to‐sample procedure. Comparisons were two additional visual stimuli, B1 and B2, and samples were A1 and A2. Reinforcers followed selections of B1 in the presence of A1 and of B2 in the presence of A2. After the simple‐discrimination and conditional‐discrimination baselines had been acquired, B1 and B2 were displayed alone (without a sample) on probe trials. Subjects had never been taught explicitly how to respond to such displays. Nonetheless, they almost always selected B1, which was involved in a conditional relation with A1, the stimulus that served as S+ on the simple‐discrimination trials. This outcome suggested the formation of stimulus classes during conditional‐discrimination training. Through class formation, B1 and B2 had apparently acquired stimulus functions similar to those shown by A1 and A2 on simple‐discrimination trials, thereby leading to emergent selections of B1 on the probes.
THE MERGER AND DEVELOPMENT OF EQUIVALENCE CLASSES BY UNREINFORCED CONDITIONAL SELECTION OF COMPARISON STIMULI
Authors: Saunders Richard R. , Saunders Kathryn J. , Kirby Kimberly C. , Spradlin Joseph E.
Published: March 2006

Three experiments assessed the likelihood that subjects with histories of equivalence class development would respond conditionally on new discriminations in the absence of differential consequences for responses. In the first two experiments, two groups of subjects with different experimental histories, but whose performances showed four equivalence classes, responded on trials without explicit reinforcement involving samples from two of the classes and comparisons from the other two classes, in a two‐choice matching‐to‐sample format. Subjects consistently selected a particular comparison in the presence of a particular sample. Subsequent tests showed the emergence of equivalence relations between stimuli from classes linked by the unreinforced conditional selections. Subsequently, in Experiment II, the subjects' responses in the conditional selection trials were reinforced if the selection was reversed from that made previously. Although reversed selection was maintained, 2 of the 3 subjects continued to perform on equivalence relation trials according to their original unreinforced selections. In the third experiment, these 2 subjects responded on a series of conditional discriminations involving three new pairs of sample stimuli and one new pair of comparison stimuli. No explicit reinforcement followed responses on any trial in this experiment. Subsequent tests for equivalence between sample stimuli revealed the development of two equivalence classes.
SELF‐CONTROL: TEACHING TOLERANCE FOR DELAY IN IMPULSIVE CHILDREN
Authors: Schweitzer Julie B. , Sulzer‐Azaroff Beth
Published: March 2006

We investigated a procedure to increase the selection of larger, more delayed reinforcers (i.e., more advantageous in the long run) over smaller immediate reinforcers, in an effort to increase a key aspect of self‐control in children. Six preschoolers, including one comparison subject, identified by their teachers as impulsive, were preassessed and found consistently to select smaller immediate reinforcers over larger, more delayed ones. The teaching procedure consisted of gradually increasing the durations of the delay interval over many sessions. The follow‐up assessments showed that 5 of these children increased the proportion of their choices of the delayed reinforcers. Before training, indifference points ranged from 1.7 to 51.7 s; following treatment, points rose to a range of 37.5 to at least 90 s, with 3 children preferring the larger reinforcer at all delay intervals tested. The results demonstrated the feasibility of teaching young children to make choices more advantageous to them in the long run.
CHOICE IN THE REPEATED‐GAMBLES EXPERIMENT
Authors: Silberberg Alan , Murray Paul , Christensen Joyce , Asano Toshio
Published: March 2006

Humans chose 10 times between two roulette wheels projected on a monitor. During the first trial, the left wheel provided a hypothetical $100 with p = .94, and the right wheel provided $250 with p = .39. A titration procedure adjusted the probability of a $250 win across trials to permit estimation of an indifference point between alternatives. In Experiment 1, intertrial‐interval duration (25 vs. 90 s) and whether sessions began with an intertrial interval or a trial were varied in a 2 × 2 design in this risky‐choice procedure. Risk aversion (preference for the $100 wheel) increased with intertrial interval but was unaffected by whether sessions began with a trial or an intertrial interval. In Experiment 2, all sessions began with a trial, and subjects were informed that the experiment ended after 10 trials. Intertrial‐interval duration had no effect on choice. In Experiment 3, intertrial‐interval duration and whether subjects were given $10 or $10,000 before beginning were varied among four groups in a 2 × 2 design. In all other ways, the procedure was unchanged from Experiment 2. Intertrial interval had no effect on choice, but the $10,000 groups showed less risk aversion than the $10 groups. These results can be explained more readily in terms of Kahneman and Tversky's (1984) notion of “framing of the prospect” than in terms of Rachlin, Logue, Gibbon, and Frankel's (1986) behavioral account of risky choice.
RESPONDING OF PIGEONS UNDER VARIABLE‐INTERVAL SCHEDULES OF UNSIGNALED, BRIEFLY SIGNALED, AND COMPLETELY SIGNALED DELAYS TO REINFORCEMENT
Authors: Schaal David W. , Branch Marc N.
Published: March 2006

In Experiment 1, three pigeons' key pecking was maintained under a variable‐interval 60‐s schedule of food reinforcement. A 1‐s unsignaled nonresetting delay to reinforcement was then added. Rates decreased and stabilized at values below those observed under immediate‐reinforcement conditions. A brief stimulus change (key lit red for 0.5 s) was then arranged to follow immediately the peck that began the delay. Response rates quickly returned to baseline levels. Subsequently, rates near baseline levels were maintained with briefly signaled delays of 3 and 9 s. When a 27‐s briefly signaled delay was instituted, response rates decreased to low levels. In Experiment 2, four pigeons' responding was first maintained under a multiple variable‐interval 60‐s (green key) variable‐interval 60‐s (red key) schedule. Response rates in both components fell to low levels when a 3‐s unsignaled delay was added. In the first component delays were then briefly signaled in the same manner as Experiment 1, and in the second component they were signaled with a change in key color that remained until food was delivered. Response rates increased to near baseline levels in both components, and remained near baseline when the delays in both components were lengthened to 9 s. When delays were lengthened to 27 s, response rates fell to low levels in the briefly signaled delay component for three of four pigeons while remaining at or near baseline in the completely signaled delay component. In Experiment 3, low response rates under a 9‐s unsignaled delay to reinforcement (tandem variable‐interval 60 s fixed‐time 9 s) increased when the delay was briefly signaled. The role of the brief stimulus as conditioned reinforcement may be a function of its temporal relation to food, and thus may be related to the eliciting function of the stimulus.
PIGEONS' CHOICES IN SITUATIONS OF DIMINISHING RETURNS: FIXED‐ VERSUS PROGRESSIVE‐RATIO SCHEDULES
Authors: Wanchisen Barbara A. , Tatham Thomas A. , Hineline Philip N.
Published: March 2006

In two different discrete‐trial procedures, pigeons were faced with choices between fixed‐ratio and progressive‐ratio schedules. The latter schedules entail diminishing returns, a feature analogous to foraging situations in the wild. In the first condition (no reset), subjects chose between a progressive‐ratio schedule that increased in increments of 20 throughout a session and a fixed‐ratio schedule that was constant across blocks of sessions. The size of the fixed ratio was varied parametrically through an ascending and then a descending series. In the reset condition, the same fixed‐ratio values were used, but each selection (and completion) of the fixed ratio reset the progressive‐ratio schedule back to its minimal value. In the no‐reset procedure, the pigeons tended to cease selecting the progressive ratio when it equaled or slightly exceeded the fixed‐ratio value, whereas in reset, they chose the fixed ratio well in advance of that equality point. These results indicate sensitivity to molar as well as to molecular reinforcement rates, and those molar relationships are similar to predictions based on the marginal value theorem of optimal foraging theory (e.g., Charnov, 1976). However, although previous results with monkeys (Hineline & Sodetz, 1987) appeared to minimize responses per reinforcement, the present results corresponded more closely to predictions based on sums‐of‐reciprocals of distance from point of choice to each of the next four reinforcers. Results obtained by Hodos and Trumbule (1967) with chimpanzees in a similar procedure were intermediate between these two relationships. Variability of choices, as well as median choice points, differed between the reset and no‐reset conditions. Although these differences are consistent with the relative costs (in responses per reinforcement) in the two procedures, the differing dispersions of choice probably arise mainly from differing structural constraints of the two procedures.
CHOICE AND FORAGING: THE EFFECTS OF ACCESSIBILITY ON ACCEPTABILITY
Authors: Fantino Edmund , Preston Ray A.
Published: March 2006

Pigeons responded in a successive‐encounters choice procedure in which accessibility of the less profitable of two outcomes varied either in terms of probability of encounter or search time to encounter (keeping search time to the more profitable outcome constant). When the less profitable outcome was made more probable its acceptance became more likely. However, when search time to encounter the less profitable outcome was shortened, its acceptance became less likely. Both results are consistent with the delay‐reduction hypothesis and with an optimality model developed for application to the successive‐encounters choice procedure.
TIME HORIZONS IN RATS: THE EFFECT OF OPERANT CONTROL OF ACCESS TO FUTURE FOOD
Authors: Timberlake William , Gawley Donald J. , Lucas Gary A.
Published: March 2006

The primary goal of this experiment was to determine whether the addition of an operant requirement for access to a less costly (continuous reinforcement) patch of future food increased the time horizon over which that future patch decreased intake in a currently available depleting (progressive‐ratio) patch. Three groups of 4 rats were tested. Each member of the earned‐time group was required to cumulate a fixed‐time outside the progressive‐ratio patch to obtain access to food in the less costly patch; the fixed‐time requirement ranged from 2 to 64 min. Rats in the matched‐time group received response‐independent access to less costly food at the average delay shown by the earned‐time group. Rats in the matched‐time no‐food group were removed from the chamber at the same average delay without receiving access to less costly food. Two of the earned‐time rats showed an increased time horizon relative to that shown by the matched‐time rats (approaching 40 min for 1 rat). The other 2 earned‐time rats markedly increased instrumental responding but showed suppression of intake only when food was less than 20 min away. The matched‐time group showed less suppression of intake over a similar range of delay intervals. Surprisingly, the matched‐time no‐food animals also showed suppression of intake concentrated at the end of the session, possibly reflecting the receipt of their entire daily ration 30 min after the session. The potential importance of time horizons to the foraging process is clear, but experimenters are still working out paradigms for investigation of these horizons.
COPING WITH RISING FOOD COSTS IN A CLOSED ECONOMY: FEEDING BEHAVIOR AND NOCTURNAL HYPOTHERMIA IN PIGEONS
Authors: Rashotte Michael E. , Henderson Dori
Published: March 2006

The pigeon's response to increasing fixed‐ratio schedules in a 24‐hr closed economy is marked by changes in feeding behavior during the daily light phase and by changes in body temperature during the dark phase. The time course of these responses to increasing behavioral cost of obtaining food is very different. Feeding is most affected immediately, within the first day of exposure to moderate fixed ratios. The number of times the pigeons produce the food hopper each day decreases, and the rate at which they eat from the food hopper (grams per minute) when it is available increases, as the fixed ratio is raised. Body temperature is affected later, falling to progressively lower resting levels during the dark phase as body weight drops at the higher fixed ratios when food intake is reduced. The changes in feeding and in body temperature that occur as the fixed‐ratio schedule increases seem to reduce daily energy expenditures, within the constraints imposed by the experiment. The ascending and descending limbs of the bitonic function obtained when total daily operant responding is plotted as a function of fixed‐ratio schedule in the closed economy is possibly related to the occurrence of thermoregulatory strategies for energy conservation. The energetic analysis of performances in the closed economy requires consideration of a variety of energetic strategies available to the species being studied.
POSITIVE BEHAVIORAL CONTRAST ACROSS FOOD AND ALCOHOL REINFORCERS
Authors: McSweeney Frances K. , Melville Cam L. , Higa Jennifer
Published: March 2006

The present study examined behavioral contrast during concurrent and multiple schedules that provided food and alcohol reinforcers. Concurrent‐schedule contrast occurred in the responding reinforced by food when alcohol reinforcers were removed. It also occurred in the responding reinforced by alcohol when food was removed. Multiple‐schedule contrast appeared for food when alcohol reinforcers were removed, but not for alcohol when food was removed. These results show that behavioral contrast may, but does not always, occur across qualitatively different reinforcers. They also show that multiple‐schedule contrast may be more difficult to produce than concurrent‐schedule contrast. The results have implications for a model of alcohol consumption.
DISCRIMINATION LEARNING IN A FORAGING SITUATION
Authors: Mellgren Roger L. , Brown Steven W.
Published: March 2006

Rats were allowed to forage in a simulated natural environment made up of eight food sources (patches) each containing a fixed number of pellets. Two of the eight contained an extra supply of peanuts. The peanut patches were signaled by an olfactory/visual cue located at the bottom of the ladder leading to the patch. In successive phases the number of sessions per day, height of the patches, and availability of peanuts were manipulated. Subjects showed evidence of discrimination learning under these conditions, although the degree of discriminatory behavior varied as a function of environmental manipulations. Assessment of behavior within foraging sessions showed that subjects systematically changed their patterns of utilization of patches across time. Sampling or exploration, as well as food reinforcement, seem implicated in these results.
CONCURRENT VARIABLE‐RATIO SCHEDULES: IMPLICATIONS FOR THE GENERALIZED MATCHING LAW
Authors: MacDonall James S.
Published: March 2006

Rats' responses were reinforced on concurrent variable‐ratio variable‐ratio schedules in which responses on one lever incremented the ratio counter and responses on a second lever changed the schedule and correlated stimulus. The relative frequency of reinforcement was varied from .10 to .99. In one set of conditions, responding on the main lever incremented both ratio counters, but reinforcement required a response in the presence of the stimulus correlated with the ratio that had been completed. In a second set of conditions, responses on the main lever incremented only the ratio correlated with the stimulus that was currently present. When main‐lever responses incremented both ratio counters, subjects distributed responding and time in a manner consistent with the generalized matching law. When responses on the main lever incremented only the schedule currently in effect, the rats responded almost exclusively on the schedule producing the higher frequency of reinforcement. These results extend the applicability of the generalized matching law to dependent ratio schedules.
BEHAVIORAL STEREOTYPY AND THE GENERALIZED MATCHING EQUATION
Authors: Pear Joseph J.
Published: March 2006

The development of behavioral stereotypy is a common result of exposure to both response‐dependent and response‐independent reinforcement procedures. The generalized matching equation and two dynamic versions of that equation, which take into account the time differential between reinforcements and their effect on behavior, predict this outcome of many procedures involving reinforcement. Following from the assumption that distinct response topographies, distinct response sequences, or orientations to distinct stimuli can be treated in the equations as distinct classes of behavior, the equations predict that—at least for matching and undermatching—the behavior class that is most biased relative to other behavior classes of the same type will tend to predominate to the exclusion or near exclusion of those behavior classes.
A QUANTITATIVE ANALYSIS OF CHAIN‐SCHEDULE PERFORMANCE
Authors: Davison Michael , McCarthy Dianne
Published: March 2006

Six pigeons were trained with a chain variable‐interval variable‐interval schedule on the left key and with reinforcers available on the right key on a single variable‐interval schedule arranged concurrently with both links of the chain. All three schedules were separately and systematically varied over a wide range of mean intervals. During these manipulations, the obtained reinforcer rates on constant arranged schedules also frequently changed systematically. Increasing reinforcer rates in Link 2 of the chain increased response rates in both links and decreased response rates in the variable‐interval schedule concurrently available with Link 2. Increasing Link‐1 reinforcer rates increased Link‐1 response rates and decreased Link‐2 response rates. Increasing reinforcer rates on the right‐key schedule decreased response rates in Link 1 of the chain but did not affect the rate in Link 2. The results extend and amplify previous analyses of chain‐schedule performance and help define the effects that a quantitative model must describe. However, the complexity of the results, and the fact that constant arranged reinforcer schedules did not necessarily lead to constant obtained reinforcer rates, precluded a quantitative analysis.
DIFFERENTIAL EFFECTS OF PENTOBARBITAL AND COCAINE ON PUNISHED AND NONPUNISHED RESPONDING
Authors: Dworkin Steven I. , Bimle Cindy , Miyauchi Tatsuo
Published: March 2006

Similar rates of punished and nonpunished responding, maintained with equated rates of reinforcement, were established in pairs of rats. One subject of each pair was exposed to a random‐ratio schedule of food presentation. The interreinforcement intervals for this subject comprised the intervals of a random‐interval schedule of reinforcement for the other (yoked) rat. The random‐ratio schedule maintained rates of responding higher than those maintained by the same rate of reinforcement schedule according to the yoked random‐interval contingency. A random‐ratio schedule of electric foot shock added to the random‐ratio schedule of food presentation suppressed rates of responding such that similar rates of responding were observed in rats of both groups. Pentobarbital (3.0 to 17.0 mg/kg) increased punished responding at doses that had little effect on or decreased nonpunished responding, whereas cocaine (5.6 to 30 mg/kg) increased nonpunished responding at doses that decreased or did not alter punished responding. Qualitatively different effects of pharmacological agents on punished and nonpunished responding can be obtained using procedures that generate similar rates and temporal patterns of punished and nonpunished responding. The effects of pentobarbital and cocaine on responding can be determined by factors other than simply the baseline rate of responding.
CHILDREN'S CHOICE: SENSITIVITY TO CHANGES IN REINFORCER DENSITY
Authors: Sonuga‐Barke Edmund J. S. , Lea Stephen E. G. , Webley Paul
Published: March 2006

Two experiments were carried out in which children's sensitivity to changes in reinforcer density (number of reinforcers per session) was measured in a choice paradigm. In Experiment 1, 24 girls (ages 6, 9, and 12 years) performed on concurrent‐chain schedules of reinforcement. The initial links were variable‐interval 10‐s schedules. One terminal link always gave three tokens after 30 s, but the parameters associated with the other were varied. Independent manipulations of reinforcer size (two tokens or four tokens) and prereinforcement delay (25 s or 65 s) led to equal changes in the relative density of tokens that could be earned on the schedules. Subjects at all ages were sensitive to changes in reinforcer density brought about by changes in reinforcer size, whereas only 3 12‐year‐olds showed sensitivity to the changes brought about by manipulation of prereinforcer delay. In Experiment 2, titration procedures were used to test the extent of this insensitivity to delay in 32 6‐ and 12‐year‐old children. In these procedures, a repeated choice of the large reinforcer increased the delay to its delivery, and a repeated choice of the small reinforcer reduced the delay to the delivery of the large reinforcer. Whereas 6‐year‐old boys and girls tended to maintain a strong preference for the large reinforcer, so increasing the delay to its delivery, 12‐year‐olds tended to distribute their responses to both alternatives, thus producing a stable level of delay to the large reinforcer. The results from the two experiments support the idea of two stages in the development of adaptive intertemporal choice.
CHOICE AND TERMINAL‐LINK RESPONSE TOPOGRAPHY
Authors: Starin Stephen
Published: March 2006

Six pigeons responded under concurrent‐chains schedules. For 3 birds, pecking was required in both initial links; for 3 others, treadle pressing was required. For all subjects, pecking was required in one terminal link and treadling in the other. The initial links consisted of independent variable‐interval 60‐s schedules. All birds were exposed to five pairs of terminal‐link variable‐interval schedules over 10 conditions: 6 s versus 54 s, 18 s versus 42 s, 30 s versus 30 s, 42 s versus 18 s, and 54 s versus 6 s. Comparisons of responding under nominally identical terminal‐link variable‐interval schedules showed that, without exception, higher choice proportions were obtained for the alternative correlated with terminal‐link pecking. Moreover, terminal‐link delay to reinforcement was shorter for terminal‐link pecking than for terminal‐link treadling chains. This factor, along with response force requirements, was implicated in explaining the present as well as previous findings of preference for pecking over treadling. It was found also that the delay‐reduction hypothesis provided only a moderately accurate description of performance under concurrent chains in which different terminal‐link response topographies are required. These findings suggest that quantitative models neglecting the effects of differing terminal‐link topographies may be incomplete.