bluuebunny/crossref_metadata_2025 huggingface dataset:
FREE‐OPERANT AVOIDANCE IN THE PIGEON USING A TREADLE RESPONSE1
Authors: Smith Richard F. , Keller Frederick R.
Published: March 2006

A free‐operant avoidance schedule was used to establish and maintain foot‐treadle responding by two Homing, one White King, and two Carneaux pigeons. In the absence of responding, the interval between shocks equaled 10 sec. Each time a treadle response occurred the shock was postponed for 32 sec. Pigeons appear to learn the treadle response more quickly and use it to avoid shock more successfully than do rats bar pressing on similar schedules. The treadle response becomes highly stereotyped and interresponse time distributions obtained from terminal behavior appear very similar to data obtained from rats. It is concluded that the difficulty in training pigeons to avoid electric shock is not in establishing avoidance behavior but in attempting to evaluate such behavior with the key‐peck response.
ON THE LAW OF EFFECT1
Authors: Herrnstein R. J.
Published: March 2006

Experiments on single, multiple, and concurrent schedules of reinforcement find various correlations between the rate of responding and the rate or magnitude of reinforcement. For concurrent schedules (i.e., simultaneous choice procedures), there is matching between the relative frequencies of responding and reinforcement; for multiple schedules (i.e., successive discrimination procedures), there are contrast effects between responding in each component and reinforcement in the others; and for single schedules, there are a host of increasing monotonic relations between the rate of responding and the rate of reinforcement. All these results, plus several others, can be accounted for by a coherent system of equations, the most general of which states that the absolute rate of any response is proportional to its associated relative reinforcement.
GENERALIZATION AND RESPONSE MEDIATION OF A CONDITIONAL DISCRIMINATION1
Authors: Eckerman David A.
Published: March 2006

Fifteen pigeons were given conditional discrimination training in which a colored sample stimulus determined which of two line comparison stimuli (vertical and horizontal) was correct. As part of the conditional discrimination procedure, birds were required to make an “observing response” to the sample stimulus presented on a wide key. The location on this key of the required observing response for the two sample stimuli differed by 0, 3, or 6 in. (0, 7.6, or 15.2 cm) for three groups of birds. Accuracy of conditional discrimination performance was directly related to the amount of separation. In subsequent generalization tests with novel sample stimuli, both observing‐response location and comparison responding changed within the same region of the wavelength continuum from that appropriate for one of the training samples to that appropriate for the other. A maintained generalization test (continued reinforcement for training stimuli) revealed this relation more strongly. A test in which observing‐response location was the only sample stimulùs of a conditional discrimination revealed stimulus control by this observing response, supporting a response mediation interpretation of the data.
RELATIVE FREQUENCY OF REINFORCEMENT AND RATE OF PUNISHED BEHAVIOR1
Authors: Lattal K. A.
Published: March 2006

After training on a multiple variable‐interval variable‐interval schedule of reinforcement, each response in one component of the schedule was followed by a brief electric shock. When the rate of punished responses stabilized, the frequency of reinforcement in the other component was first decreased and then increased from the baseline frequency. The effects of these manipulations were consistent with reports of interactions in multiple schedules involving only unpunished behavior, i.e., the rate of punished responses increased with a higher relative frequency of reinforcement in the punishment component and decreased with a lower relative frequency of reinforcement in that component. The relevance of such findings to a further generality of behavioral contrast effects is discussed.
PAVLOVIAN CONDITIONING OF SHOCK‐ELICITED AGGRESSION: A DISCRIMINATION PROCEDURE1
Authors: Lyon David O. , Ozolins Delmar
Published: March 2006

Two auditory stimuli, separated by a fixed intertrial interval, were alternately presented to two rats in a closed environment. The positive conditioned stimulus (CS+) terminated with the offset of a 2‐mA, 0.75‐sec shock. The negative conditioned stimulus (CS−) terminated without shock. The incidence of the “stereotyped fighting posture” was recorded during the CS+, the CS−, the intertrial interval, and shock. The results showed an increase in the percentage of conditioned responses during the CS+, and a decrease during both the CS− and the intertrial interval, when the duration of the conditioned stimuli and the intertrial interval was 16 sec. Appropriate changes in the incidence of aggression during the two stimuli were obtained following the reversal of the stimulus functions. During the acquisition and reversal phases there was a between‐session decrement and a within‐session improvement in the incidence of aggression during the CS+, defined as warm‐up: The presentation of free shocks before the conditioning sessions was effective in reducing the warm‐up only when the interval between shocks was 64 sec. These data were interpreted as demonstrating classical conditioning of shock‐elicited aggression, with little chance of non‐associative factors contributing to the measurement of the conditioned response.
FORGETTING AND CONDITIONED SUPPRESSION: ROLE OF A TEMPORAL DISCRIMINATION1
Authors: Hammond L. J. , Maser Jack
Published: March 2006

Several experiments have found complete retention of conditioned suppression when overall suppression to the signal for shock was measured. The present experiment examined retention of conditioned suppression but did so with a paradigm that produced temporal discrimination of shock occurrence. Nine rats were exposed to a flashing light signal of 5‐min duration that always terminated with a shock. After several months, a temporal discrimination was well established, as shown by maximum suppression toward the end of the signal period. After remaining in the home cage for 25 days, the rats were again subjected to the conditioning procedure. The overall level of suppression remained the same but the temporal discrimination was not observed.
EFFECTS OF A CONDITIONED REINFORCER UPON ACCURACY OF MATCH‐TO‐SAMPLE BEHAVIOR IN PIGEONS1
Authors: Clark Hewitt B. , Sherman James A.
Published: March 2006

Three pigeons were trained to perform a two‐key sequential match‐to‐sample task. During baseline conditions, food reinforcement was contingent upon the first match response to occur following 8‐min periods, and orange illumination of both keys preceded the delivery of food by 0.5 sec. The baseline schedule of food reinforcement was in effect throughout the study. In some conditions, a 0.5‐sec flash of orange keylight alone was presented contingent upon mismatch responses that followed variable time periods averaging 1 min. Rate of mismatch responses increased and accuracy of matching performances decreased as compared with baseline conditions. The ability of the 0.5‐sec orange flash to reinforce mismatch responses was markedly reduced when it no longer immediately preceded the delivery of food.
CONDITIONED SUPPRESSION AND CONDITIONED ENHANCEMENT WITH THE SAME POSITIVE UCS: AN EFFECT OF CS DURATION
Authors: Meltzer Donald , Brahlek James A.
Published: March 2006

Previous experiments have shown that positively reinforced operant responding is suppressed during a conditioned stimulus terminated with an electric shock (conditioned suppression). In the present experiment, the conditioned stimulus was terminated with a positive unconditioned stimulus, and it was found that the duration of the conditioned stimulus was a key factor in determining whether response suppression or response enhancement was observed during the stimulus. The lever‐pressing responses of rats were maintained by a variable‐interval schedule of food reinforcement. While the rats were pressing the lever, a light was occasionally turned on, its offset coincident with a brief period of access to a sucrose solution. In consecutive blocks of sessions, the light duration was 40 sec, 12 sec, or 120 sec. Results showed that the rate of lever pressing was substantially suppressed during the 12‐sec stimulus, slightly suppressed during the 40‐sec stimulus, and enhanced during the 120‐sec stimulus.
THE EFFECTS OF STIMULI FOLLOWED BY RESPONSE‐INDEPENDENT SHOCK ON SHOCK‐AVOIDANCE BEHAVIOR1
Authors: Pomerleau O. F.
Published: March 2006

Four rhesus monkeys were trained on a non‐discriminated shock‐avoidance schedule (baseline). Stimuli followed by response‐independent shock were then presented with the avoidance baseline no longer in effect. The main portion of the experiment consisted of superimposing (independently of responding) the stimuli followed by response‐independent shock on the avoidance baseline. Different temporal values of stimulus duration and delay of shock (produced by an avoidance response) were presented successively, using each subject as his own control. When the stimulus duration was short or the delay of shock was long, so that avoidance rate during the stimulus could assume any value without resulting in baseline (avoidable) shocks during the stimulus, a lowered or “suppressed” rate of responding developed during the stimulus. When the stimulus duration was long or the delay of shock was brief, so that avoidable shocks resulted from a response decrement during the stimulus, high or “facilitated” rates of responding developed for a large proportion of the time that the stimulus was present.
INHIBITORY STIMULUS CONTROL IN CONCURRENT SCHEDULES1
Authors: Beale I. L. , Winton A. S. W.
Published: March 2006

Six pigeons were exposed to two keys, a main key and a changeover key. Pecking the main key was reinforced on a variable‐interval 5‐min schedule when the key was blue and never reinforced when the key displayed a vertical line on a blue background. Each peck on the changeover key changed the stimulus displayed on the main key. Each subject was given two generalization tests, consisting of presentations on the main key of six orientations of the line on the blue background, with no reinforcements being given. In one test changeover‐key pecks changed the stimulus; in the other test the changeover key was covered and the experimenter controlled stimulus changes. Both responses to the six stimuli and time spent in the presence of the stimuli gave U‐shaped gradients when the changeover key was operative. With most subjects, absolute rates of responding to each stimulus produced unsystematic gradients, whether or not the changeover key was operative.
POLYDIPSIA INDUCED IN THE RAT BY A SECOND‐ORDER SCHEDULE1
Authors: Rosenblith Joan Z.
Published: March 2006

Drinking was studied in rats pressing a bar on a second‐order schedule in which every third completion of a 1‐min fixed interval was followed by food presentation. A brief flash of light signaled the completion of each fixed‐interval component. The rats drank not only after the food presentations but also after presentations of the light flash alone. A high rate of steady drinking followed intervals terminated by a food presentation. Drinking that followed intervals terminated by a light flash alone was of comparable rate, but characteristically interrupted by bar pressing. When 250‐mg food pellets were used instead of 45‐mg pellets, both drinking and bar‐pressing rates increased substantially.
AN EXTINCTION‐INDUCED INCREASE IN AN AGGRESSIVE RESPONSE WITH HUMANS1
Authors: Kelly J. F. , Hake D. F.
Published: March 2006

Nine subjects, 14 to 18 yr old, pulled a knob on a schedule of monetary reinforcement. Concurrently, they escaped or avoided periodic presentations of a tone by pressing a button that required 1.5 lb (6.67 N) of force or by punching a padded cushion that required 20 lb (88.96 N) of force. The punching response was designated as an aggressive response because the force of this response together with its topography was comparable to responses of humans that deface objects and produce escape or counter aggression from other humans. It was found that button pressing was the preferred concurrent avoidance response and there were few punches. However, when the monetary reinforcer was discontinued (extinction) punching increased for seven of the nine subjects, but there was no consistent change in the rate of button pressing. When the punching response was replaced by another non‐preferred but non‐aggressive response, neither this response nor button pressing increased during extinction. Hence, the increase in punching during extinction cannot be attributed solely to the fact that it was a concurrent response or a non‐preferred response.
POSITIVE REINFORCEMENT AND SUPPRESSION FROM THE SAME OCCURRENCE OF THE UNCONDITIONED STIMULUS IN A POSITIVE CONDITIONED SUPPRESSION PROCEDURE1
Authors: Hake D. F. , Powell J.
Published: March 2006

Responding of rats was maintained on a variable‐interval schedule of food reinforcement. The same response also produced a blinking light followed by electrical brain stimulation according to a fixed‐interval schedule. This conjoint schedule produced two behavioral changes. First, instead of a steady rate of responding throughout the session, which would be characteristic of the variable interval food schedule alone, responding between occurrences of the light‐brain stimulation pairings became positively accelerated and thus was more characteristic of the fixed‐interval schedule of these pairings. Second, food responding was suppressed during the light that preceded brain stimulation. These results indicate that positive reinforcement and suppression resulted from the same occurrence of the light‐brain stimulation combination. This finding suggests that stimuli such as conditioned reinforcers that precede an unconditioned reinforcer may have a suppressive effect upon responding in their presence that is being maintained by another reinforcer.
NEGATIVE REINFORCEMENT WITHOUT SHOCK REDUCTION1
Authors: Hineline Philip N.
Published: March 2006

Stable lever‐press responding in rats was reliably produced and maintained by a procedure in which responses could delay shocks without affecting overall shock frequency. Responding was not maintained when the delay‐of‐shock involved an increase in overall shock frequency.
SCHEDULE‐INDUCED AGGRESSION AS A FUNCTION OF FIXED‐RATIO VALUE1
Authors: Cherek D. R. , Pickens Roy
Published: March 2006

Pigeons responding for food on fixed‐ratio reinforcement schedules attacked live target birds when the ratio value was increased, but not when the value was decreased. The frequency of attacks peaked several days after ratio value change, and then gradually decreased to an original level.
THE EFFECT OF SHOCK INTENSITY UPON RESPONDING UNDER A MULTIPLE‐AVOIDANCE SCHEDULE
Authors: Powell Robert W.
Published: March 2006

The effect of two shock intensities (1.00 and 2.00 mA) were studied in the acquisition, maintenance, and extinction of unsignalled avoidance by albino rats. Single and multiple avoidance schedules were employed, with shock intensity being the principal condition that differed between schedule components. The higher shock intensity was generally more effective in producing avoidance. Higher response rates and lower shock rates were observed under high‐intensity shock when performance stabilized. When the multiple schedule was introduced, the six rats trained under a single shock intensity all showed poorer performance under the new shock intensity, whether it was higher or lower than the training intensity. Performance under the original shock intensity did not change substantially with the introduction of a different shock intensity in the other multiple schedule component. Performance under the new shock intensity showed gradual improvement with continued exposure to it. All of the rats showed persistent “warm‐up”, receiving approximately 40% of the total session shocks in the first one‐sixth of the session. The degree of warm‐up was unrelated to avoidance shock intensity.
AUDITORY FREQUENCY GENERALIZATION IN THE GOLDFISH (CARASSIUS AURATUS)1
Authors: Fay Richard R.
Published: March 2006

Auditory frequency generalization in the goldfish was studied at five points within the best hearing range through the use of classical respiratory conditioning. Each experimental group received single‐stimulus conditioning sessions at one of five stimulus frequencies (100, 200, 400, 800, and 1600 Hz), and were subsequently tested for generalization at eight neighboring frequencies. All stimuli were presented 30 db above absolute threshold. Significant generalization decrements were found for all subjects. For the subjects conditioned in the range between 100 and 800 Hz, a nearly complete failure to generalize was found at one octave above and below the training frequency. The subjects conditioned at 1600 Hz produced relatively more flat gradients between 900 and 2000 Hz. The widths of the generalization gradients, expressed in Hz, increased as a power function of frequency with a slope greater than one.
PUNISHMENT OF ELICITED AGGRESSION
Authors: Azrin N. H.
Published: March 2006

Aversive shocks are known to produce aggression when the shocks are not dependent on behavior and to suppress behavior when the shocks are arranged as a dependent punisher. These two processes were studied by presenting non‐dependent shock to monkeys at regular intervals, thereby producing biting attacks on a pneumatic tube. Immediate shock punishment was simultaneously delivered for each biting attack. The attacks were found to decrease as a function of increasing punishment intensity. These results show that aggression is eliminated by direct punishment of the aggression even when the stimulus that is used as a punisher otherwise causes the aggression.
SUMMATION OF PUNISHMENT SUPPRESSION1
Authors: Houten Ronald Van , Rudolph Robert
Published: March 2006

In two experiments, eight rats were trained to lever press with food on a variable‐interval schedule. Bar pressing produced shock on a variable‐interval schedule in the presence of two independently presented stimuli, a light and a tone. Two rats in each experiment received alternative presentations of the light and the tone and were consequently always in the presence of a stimulus that signalled variable‐interval punishment. The other two rats in each experiment were treated similarly except that they received periods in which neither light nor tone was present. During these periods, bar pressing was not punished. The two stimuli that signalled punishment were then presented simultaneously to evaluate the effect of stimulus compounding on response suppression. The subjects trained without punishment‐free periods did not show summation to the compound stimulus; the subjects trained with punishment‐free periods showed summation of suppression. The major difference between the two experiments was the longer mean interval of variable‐interval punishment used in the second experiment. This manipulation made the summation effect more resistant to extinction and thus increased its magnitude.
COLOR ALTERNATION LEARNING IN THE PIGEON UNDER FIXED‐RATIO SCHEDULES OF REINFORCEMENT1
Authors: Williams Ben A.
Published: March 2006

Pigeons were trained on a non‐spatial delayed alternation task in which the correct stimulus was that color not responded to on the preceding trial. Subjects required to emit either 15 or 30 pecks to the correct stimulus within a trial learned the task, those required to emit only one or five pecks did not. Also, alternation was learned more easily after an incorrect than after a correct trial. Later experiments showed that a minimum fixed‐ratio value was required for successful color alternation to occur, even though no fixed‐ratio requirement was necessary when a position cue was available. The mechanism of the fixed‐ratio effects derived from the pigeons' tendency to repeat their response in the presence of the color reinforced on the last trial. Whereas subjects trained on larger fixed‐ratios corrected this error tendency within a trial, subjects trained on smaller fixed ratios did not.
CONTROL OF CONCURRENT AVOIDANCE AND APPETITIVE BEHAVIORS BY AN INDICATOR OF SHOCK PROXIMITY1
Authors: Dardano J. F.
Published: March 2006

Two monkeys were exposed to concurrent schedules in which every fifth response on one lever had the dual consequences of delivering food and stepping a 20‐step light counter upward; responses on a second lever stepped the light downward. By responding appropriately on each lever, a ration of food could be obtained without exposure to a brief shock that occurred when the counter reached the twentieth step. Behavioral patterns of light‐counter control were analyzed when the monkeys were handicapped by several types of discontinuities in the 20‐step counter: (1) different sets of four consecutive lights inoperative, (2) the upper or lower 10 steps inoperative, and (3) all lights inoperative. Generally, the monkeys maintained the light in the upper five steps of the 20‐step light counter if the lights immediately preceding the shock position were functional. However, when these counter positions were inoperative, subjects maintained the counter around the highest operative position. With all positions of the light counter inoperative, no systematic pattern of responding on the food and avoidance levers occurred.
POSITIVE CONDITIONED SUPPRESSION: EFFECTS OF CS DURATION1
Authors: Miczek Klaus A. , Grossman Sebastian P.
Published: March 2006

During a brief conditioned stimulus (15 or 30 sec) that terminated with the response‐independent delivery of banana pellets, operant responding reinforced by other food pellets according to a variable‐interval schedule of reinforcement was suppressed in the squirrel monkey. Conditioned stimuli of longer duration (1, 2, and 3 min) did not reliably affect the rate of operant performance. Brief conditioned stimuli generated homogeneous response patterns of nearly complete suppression. Increasing the CS duration did not enhance responding, as previously reported, but led to alternate bursting and pausing, which suggested a loss of control by the conditioned stimulus. The results suggest that the magnitude of “positive” or “negative” conditioned suppression reflects the strength of the classical conditioning process.
PERCENTAGE REINFORCEMENT OF FIXED‐RATIO AND VARIABLE‐INTERVAL PERFORMANCES1
Authors: McMillan John C.
Published: March 2006

Twenty to seventy per cent of the reinforcements scheduled for pigeons' fixed‐ratio 80 performances were replaced by a 4‐sec timeout. Pauses after reinforced ratios were unchanged at 80% reinforcement, but were lengthened at lower reinforcement percentages. Pauses after nonreinforced ratios were shorter than post‐reinforcement pauses. When 50% of the reinforcements arranged by a variable‐interval 60‐sec schedule were replaced by a 4‐sec timeout, pauses after reinforcement omission increased. Both frustrative nonreward and reinforcement aftereffects notions can explain the fixed‐ratio results; neither easily explains the variable‐interval data.
TRANSFER OF STIMULUS CONTROL: MEASURING THE MOMENT OF TRANSFER1
Authors: Touchette Paul E.
Published: March 2006

Three severely retarded boys acquired simple form discriminations errorlessly. Each was first taught to press a red key versus a simultaneously present white key. After this discrimination had been established, black figures were superimposed on the red and white keys. Each correct response affected the next trial by delaying the onset of the red stimulus an additional 0.5 sec. Transfer of stimulus control to the figures was indicated when the subjects responded correctly before the onset of the red stimulus. A series of errorless discrimination reversals was accomplished with this technique, during which the number of trials to transfer systematically decreased with successive reversals.
CONTRAST AND STIMULUS GENERALIZATION FOLLOWING PROLONGED DISCRIMINATION TRAINING1
Authors: Hearst Eliot
Published: March 2006

Different groups of pigeons received discrimination training in which the reinforcement‐associated and extinction‐associated stimuli were respectively either (a) a line tilt vs a blank key, (b) a blank key vs a line tilt, or (c) two different line tilts. The high response rates that developed to the positive stimulus in all groups during discrimination learning were maintained over 64 sessions of training. After these sessions, all subjects were tested for stimulus generalization along the line‐tilt dimension. Gradients of relative (per cent) generalization around the stimulus associated with reinforcement (so‐called excitatory gradients) and around the stimulus associated with extinction (so‐called inhibitory gradients) were as steep as they typically are after much briefer training periods. These results do not support several of Terrace's predictions on the basis of the hypothesis that emotional responses develop to the stimulus associated with extinction during discrimination learning with errors, but eventually dissipate after extended training.
DIFFERENTIAL RESPONDING AS A FUNCTION OF AUDITORY STIMULUS INTENSITY WITHOUT DIFFERENTIAL REINFORCEMENT1
Authors: Blue Scot , Sherman J. Gilmour , Pierrel Rosemary
Published: March 2006

Two groups of four rats each were trained to bar press on a variable‐interval 2‐min schedule. During training, either 3, 5, or 9 auditory stimuli of various intensities were randomly presented. A direct relationship between stimulus intensity and rate of responding was obtained, but it was more consistent in the group trained initially with three stimuli than for the group that started with nine stimuli. The results are related to the concept of stimulus intensity dynamism and the necessary conditions for the acquisition of stimulus control.
SEQUENCE SCHEDULES OF REINFORCEMENT1
Authors: Marr M. Jackson
Published: March 2006

The performance of pigeons was studied under a second‐order schedule composed of fixed‐interval components, each of which was associated with a different discriminative stimulus, the stimuli occurring in a fixed order. In one condition, food presentation followed the completion of the fourth component. This was designated a fixed‐ratio sequence schedule. In another condition, responses in the first component completed after a fixed time were reinforced. This was designated a fixed‐interval sequence schedule. Although the stimulus order and maximum reinforcement frequency were identical under the two schedules, considerably more responding occurred under the fixed‐interval sequence schedule in all components. Relatively few food presentations occurred after responding during any but the terminal components of the fixed‐interval sequence schedule, a feature independent of the parameter values investigated. In addition, while a pattern of increased responding between food presentations prevailed under both schedules, under the fixed‐interval sequence schedule the rate in the terminal component was frequently less than in the penultimate component. The fixed‐interval sequence schedule appeared to have several properties of simple fixed‐interval schedules.
THE VISUAL ACUITY OF THE PIGEON FOR DISTANT TARGETS1
Authors: Blough Patricia M.
Published: March 2006

The acuity of six pigeons was measured in an apparatus that required the birds to make visual discriminations at a distance of 28.75 in. (73 cm) from the stimulus targets. The stimuli were black and white gratings of varying stripe width. A forced choice procedure was used, and both the Method of Constant Stimuli and a descending series technique determined the order of stimulus presentation. Thresholds, obtained by interpolating at the 25% error point on the psychometric functions, ranged from 1.16 to 4.0 min of arc. Thresholds measured in the same apparatus for two human observers were 0.79 and 0.82 min of arc. The descending series design produced lower per cent error rates at the widest stripe value, but otherwise there appeared to be no difference between psychophysical methods. Position preferences occurred in most of the birds; differential per cent error functions and differential latency functions to the two keys illustrate these. Retinal histology revealed shallow, centrally located foveae in the three pigeon breeds used.
COLLATERAL BEHAVIOR OF THE PIGEON DURING CONDITIONED SUPPRESSION OF KEY PECKING1
Authors: Stein Norman , Hoffman Howard S. , Stitt Christopher
Published: March 2006

Ethological recording procedures measured collateral behavior in pigeons whose key‐pecking performance was suppressed during a tone that ended with unavoidable electric shock. Independent recordings of gross behavior were made by two observers throughout 60‐sec intervals immediately before, during, and after tone presentation. Results indicated significant reductions in the frequency of collateral movements and an increase in the time between successive movements during tone presentations. These effects were observed in all subjects, despite differences in the sequential patterns of behavior. Only partial recovery of the behavior evidenced before tone presentation was found during a 60‐sec interval following shock. It was concluded that conditioned suppression procedures caused the bird to “freeze” during tone presentation and in this fashion produced a general inhibitory effect on ongoing overt activity, including key pecking.
SIGNAL FUNCTIONS IN DISCRIMINATED AVOIDANCE BEHAVIOR1
Authors: Gilbert R. M.
Published: March 2006

Four rats were trained to lever press under a discriminated avoidance/escape schedule in which separately signalled safe and warning periods were 100 sec and 32 sec respectively. The auditory and not the visual component of the compound warning signal became associated with the discriminative control of lever pressing. Avoidance behavior also came under temporal control, in that the probability of lever pressing increased as the warning period progressed. Timing began with the onset of the warning signal rather than the offset of the safe signal. However, after the warning signal had been progressively eliminated, timing began with the offset of the safe signal. When neither signal was normally available, the temporal distribution of avoidance behavior changed markedly. Drifts in the temporal distribution of lever pressing occurred throughout the study; these were manipulated for two animals.
THE RELATIVE AVERSIVENESS OF SIGNALLED VS UNSIGNALLED AVOIDANCE
Authors: Badia Pietro , Culbertson Stuart , Lewis Paul
Published: March 2006

Subjects avoided shock by pressing on one lever under an unsignalled condition, but by pressing a separate lever they changed the condition to signalled avoidance for 1‐min periods. Signalled avoidance periods were identified by a correlated stimulus. All eight subjects responded to change the unsignalled schedule to a signalled one. Once contact with signalled avoidance was made, subjects continued responding to remain in that condition. Other tests showed that changeover responding was greater when the correlated stimulus was presented without the signal than when the signal was presented without the correlated stimulus. An analysis based upon shock and shock‐free periods is presented.
RESPONSE‐DEPENDENT AND RESPONSE‐INDEPENDENT TIMEOUT FROM AN AVOIDANCE SCHEDULE1
Authors: Baron Alan , Trenholme Irene A.
Published: March 2006

While rats were responding in a single‐lever apparatus to avoid electric shock, a signal was presented and followed by a 5‐min timeout period when all shocks were omitted. For the response‐dependent member of each yoked pair, the first response 60 sec after onset of the pre‐timeout signal terminated the signal and initiated timeout. The other, yoked animal was exposed to the same sequence except that signal termination and timeout onset were response independent. Under the response‐dependent condition, response rates in the presence of the signal increased relative to baseline rates. Rate increases also occurred when timeout was response independent, but were of lesser magnitude and reliability. Subsequent reversal of the yoking arrangement produced stable and equivalent rate increases under both conditions. Other findings were that increased rates in the presence of the signal diminished when timeout was omitted but were maintained for a time on an avoidance‐extinction baseline. In general, the results supported the conclusion of previous experiments that timeout from avoidance can serve as a positive reinforcer. The finding that response‐independent presentation of timeout produced rate increases, particularly after a history with response‐dependent timeout, was interpreted in terms of adventitious reinforcement of previously established behavior.
ON THE FORM OF STIMULUS GENERALIZATION CURVES FOR VISUAL INTENSITY1
Authors: Ernst A. John , Engberg Larry , Thomas David R.
Published: March 2006

Twelve pigeons were given successive discrimination training involving variable‐interval reinforcement for key pecking in the presence of one intensity of monochromatic light randomly alternated with extinction for pecking during another intensity. All of the pigeons were then tested in extinction for generalization along the intensity dimension, and all showed a displacement of maximal responding from the positive stimulus in the direction opposite the negative stimulus. For six of the pigeons, for which the test included only three values beyond the positive stimulus, four showed peaked gradients but two did not, showing monotonic gradients with maximal responding to the most extreme test value. For another six pigeons tested over a wider range, all showed peaked gradients. Thus, when a sufficiently wide range of test values is employed, generalization gradients for visual intensity have the same peaked form as do gradients for qualitative visual dimensions such as wavelength or line angle.
APPARENT MOVEMENT AND REAL MOVEMENT DETECTION IN THE PIGEON: STIMULUS GENERALIZATION
Authors: Siegel R.K.
Published: March 2006

Pigeons were trained to discriminate apparent movement and real movement in visual displays showing horizontal movement. Generalization testing on the dimension of directional movement yielded gradients that sloped as movement changed from horizontal to vertical. Evidence of generalization between apparent movement and real movement was found in equivalent response rates to training displays of either type. Extremely low response rates to training displays pulsating but showing no movement eliminated flicker as the basis of the discrimination.
SOME EFFECTS OF RESPONSE INDEPENDENT REINFORCERS IN MULTIPLE SCHEDULES1
Authors: Lattal K. A. , Maxey G. C.
Published: March 2006

In Exp. I, rats' lever presses were conditioned on multiple variable‐interval variable‐interval schedules. Changing one of the multiple schedule components to variable time reduced responding in that component. Further reductions in responding occurred in both components when the schedule was changed to multiple variable‐time variable‐time. After reinstating the multiple variable‐interval variable‐time schedule, lower response rates were maintained in the variable‐time component during a series of stimulus reversals. In Exp. II, replacement of extinction components of multiple variable‐interval extinction or multiple extinction extinction with variable‐time schedules for single sessions (probe) resulted in response rate increments in those components. In the former schedule these increases were concomitant with response decreases during the variable‐interval components. Response increases in the variable‐time probes were related to conditioning history and, as a result, to response probability at the time of the probe.
RATES AND PATTERNS OF RESPONDING WITH CONCURRENT FIXED‐INTERVAL AND VARIABLE‐INTERVAL REINFORCEMENT1
Authors: Nevin John A.
Published: March 2006

Pigeons were exposed to concurrent fixed‐interval and variable‐interval schedules of food reinforcement on two keys. The times between reinforcement were varied systematically on both keys. The overall relative frequency of responding on the fixed‐interval key depended on the relative frequency of reinforcement, but did not match it. Instead, the ratio of responses on the fixed‐interval key to responses on the variable‐interval key was a power function of the ratio of reinforcements, with an exponent of 0.5. Patterns of responding between reinforcements on the fixed‐interval key depended on both relative and absolute values of the reinforcement schedules. Similar overall relative responding was obtained at different absolute schedule values with equal relative reinforcement, despite some differences in patterns of responding.
EFFECTS OF SYMMETRICAL AND ASYMMETRICAL CHANGEOVER DELAYS ON CONCURRENT PERFORMANCES1
Authors: Pliskoff Stanley S.
Published: March 2006

Two variable‐interval 3‐min schedules functioned concurrently to arrange reinforcement of a pigeon's pecks on a single key, the main key. Each schedule was associated with a distinct color of the main key; a response on a second key alternated the color and schedule assignment of the main key. A changeover delay, a period of time following schedule and key‐color alternation during which reinforcement of responding on the main key could not occur, was arranged with equal or with unequal durations for the two directions of alternation. Durations were varied from 0.33 sec to 27 sec, in addition to no delay. With equal delays for the two directions of alternation, the pigeon alternated the schedules less often the larger the delay duration. When the delays in the two directions of alternation were unequal, it could be shown that alternation of the schedules was reduced both by a delay just incurred by the last alternation and by a. delay to be incurred by the next. The latter delay was more potent in reducing the frequency of alternations.
STIMULUS AND SUBJECT CONTROL OF SCHEDULE‐INDUCED DRINKING
Authors: Keehn J. D. , Colotia V. A.
Published: March 2006

Responding in three food‐deprived rats was reinforced on schedules in which reinforcement periods (fixed‐ratio 1 or 2 for 1, 3, 6, 9, 14, or 21 reinforcers) alternated with extinction intervals. Schedule‐induced drinking occurred and was mostly confined to the onset of extinction intervals. Drink durations were longer after 21‐pellet meals but were not reliably different after 1, 3, 6, or 9‐pellet meals. When termination of the extinction intervals was response dependent, schedule‐induced drinking diminished until minimum extinction intervals of 15, 30, and 60 sec were introduced.
COMPOUNDING OF DISCRIMINATIVE STIMULI FROM THE SAME AND DIFFERENT SENSORY MODALITIES1
Authors: Miller Laurence
Published: March 2006

Rats' responding was maintained by fixed‐interval schedules of reinforcement in the presence of a tone or two separate lights. The lights were either of low, moderate, or high intensity. Compounds of these single discriminative stimuli each maintained a greater frequency of response than did the single stimuli, and the compound composed of stimuli from different sensory modalities (light + tone) maintained a greater level of responding than did the compound composed of stimuli from the same sensory modality (light + light). Combining lights of different intensity had no differential effect on responding. However, in the second experiment, a compound composed of a light and a tone, each of greater intensity than the light and tone of another compound, initially maintained a higher frequency of response, demonstrating intensity effects during stimulus compounding when the increase in intensity occurs through the component stimuli. This intensity effect, however, was only transitory.
TWO‐KEY CONCURRENT PACED VARIABLE‐INTERVAL PACED VARIABLE‐INTERVAL SCHEDULES OF REINFORCEMENT1
Authors: Moffitt Marilynne , Shimp Charles P.
Published: March 2006

Nine pigeons were used in two experiments in which a response was reinforced if a variable‐interval schedule had assigned a reinforcement and if the response terminated an interresponse time within a certain interval, or class, of interresponse times. One such class was scheduled on one key, and a second class was scheduled on a second key. The procedure was, therefore, a two‐key concurrent paced variable‐interval paced variable‐interval schedule. In Exp. I, the lengths of the two reinforced interresponse times were varied. The relative frequency of responding on a key approximately equalled the relative reciprocal of the length of the interresponse time reinforced on that key. In Exp. II, the relative frequency and relative magnitude of reinforcement were varied. The relative frequency of responding on the key for which the shorter interresponse time was reinforced was a monotonically increasing, negatively accelerated function of the relative frequency of reinforcement on that key. The relative frequency of responding depended on the relative magnitude of reinforcement in approximately the same way as it depended on the relative frequency of reinforcement. The relative frequency of responding on the key for which the shorter interresponse time was reinforced depended on the lengths of the two reinforced interresponse times and on the relative frequency and relative magnitude of reinforcement in the same way as the relative frequency of the shorter interresponse time depended on these variables in previous one‐key concurrent schedules of reinforcement for two interresponse times.
BEHAVIORAL CONTRAST AS A FUNCTION OF THE DURATION OF AN IMMEDIATELY PRECEDING PERIOD OF EXTINCTION1
Authors: Wilton R. N. , Clements R. O.
Published: March 2006

For four pigeons key‐peck responding was reinforced on a variable‐interval reinforcement schedule in the presence of a vertical white line. When response rates had stabilized a horizontal white line was introduced, in the presence of which reinforcement was not available (extinction). The horizontal line was presented once per session, immediately before the vertical line was presented. The duration of the horizontal line varied randomly from session to session, being either 0 sec (i.e., no presentation), 10 sec, 30 sec, 2 min, 10 min, 40 min, or 120 min. When the horizontal line was present for more than 0 sec, behavioral contrast was obtained in the presence of the following vertical line. Contrast increased with increasing durations of the horizontal line, asymptoting when the horizontal line was present for 40 min.
SIGNAL FREQUENCY AND SHOCK PROBABILITY AS DETERMINANTS OF PROLONGED VIGILANCE PERFORMANCE IN RHESUS MONKEYS
Authors: Krasnegor Norman A. , Brady Joseph V.
Published: March 2006

The effects of changing signal frequency on a prolonged vigilance task were investigated by systematically increasing the average inter‐trial interval between successive signals. During a 6‐hr watch, vigilance performance remained constant when the rate of signal presentation was 40, 20, and 10 per hour. When the rate of signal presentation was reduced to 7 or 4 per hour, marked decrements in detection performance were observed. Similar vigilance decrements occurred when the average rate of signals per hour was kept constant (10 per hour) and the probability of receiving a shock for missing a signal was systematically varied. The results of this study indicate the importance of reinforcement factors in the control and maintenance of vigilance performance.
LICK‐SHOCK CONTINGENCIES IN THE RAT1
Authors: Quinsey Vernon L.
Published: March 2006

Hungry rats were allowed to lick an 8% sucrose solution and then one of four lick‐shock contingency conditions was superimposed on the licking baseline. These conditions were: free‐operant avoidance, free shock, punishment, and no shock. From highest to lowest response rates, the groups fell in the order—avoidance, no shock, free shock, and punishment. Lick rates adjusted rapidly to introduction and removal of the contingencies. Post‐shock responding was lowest in the punishment condition and highest in the free shock condition. No method was found simultaneously to equate shock frequency and separate response rates for the three shock contingency conditions. Only small, or no, reductions in shock rate occurred over sessions under the free‐operant avoidance schedule when the shock‐shock interval was 10 sec but large reductions occurred when the shock‐shock interval was reduced to either 1 or 2 sec.
CONCURRENT PERFORMANCES: SYNTHESIZING RATE CONSTANCIES BY MANIPULATING CONTINGENCIES FOR A SINGLE RESPONSE1
Authors: Catania A. Charles
Published: March 2006

An earlier experiment scheduled variable‐interval reinforcement for pigeons' pecks on one key, and variable‐interval reinforcement alternating with extinction, in a multiple schedule, for pecks on a second key. During the second key's extinction component, first‐key pecking was relatively slow and continuous, rarely interrupted by second‐key pecking; during the variable‐interval component, first‐key pecking was frequently interrupted by second‐key pecking. When changeover delays operated, so that reinforced pecks on one key could not follow closely upon changeovers from the other key, rapid first‐key pecking between interruptions compensated sufficiently for the time lost in second‐key pecking that the overall rate of first‐key pecking remained roughly constant across the alternating multiple‐schedule components. The present experiments duplicated, on a single key, the temporal pattern of first‐key pecking generated in the earlier experiments: components of continuous key availability were alternated with components of interrupted key availability. Approximately constant overall rates of responding were observed with a single‐key equivalent of a changeover delay scheduled after interruptions and with manipulations of the on‐off durations of the interruption cycle. Rate constancies in the original concurrent situation presumably depended on analogous contingencies that operated upon the concurrent responses, rather than on any constant “reserve” of responses.
RESPONSE CONTROL WITH TITRATION OF PUNISHMENT1
Authors: Rachlin Howard
Published: March 2006

Pigeons and rats were exposed to multiple schedules with different schedules of electric shock superimposed on identical schedules of food reinforcement during each of two components. During one component, (adjusting‐intensity) the intensity of electric shock depended on responding. Each response increased the intensity while intensity decreased between responses. During the other component (constant‐intensity) the intensity was fixed at the value at which it had been adjusted at the end of the immediately preceeding adjusting‐intensity component. In one experiment, shock was continuous during both components. In another experiment, instead of continuous shock, a brief pulse was delivered immediately after each response. During the adjusting‐intensity component of both experiments, pigeons and rats responded at a rate just sufficient to keep the shock constant (critical rate). During the constant‐intensity component, responding depended on whether shock was delivered continuously or in pulses. When shock was continuous, response rate during the constant‐intensity component was higher than the critical rate. When shock was pulsed, response rate during the constant‐intensity component was equal to the critical rate.