Differential reinforcement of other behavior (DRO): a yoked-control comparison

After training to press a lever on a variable-interval 30-sec schedule, one group of rats was shifted to a differential-reinforcement-of-other-behavior 10-sec schedule, while a second group was shifted to a noncontingent yoked-control schedule that provided the same frequency and distribution of reinforcement. Then, both groups were extensively retrained on the variable-interval schedule, after which the first group was shifted to a series of differential-reinforcement-of-other-behavior 30-sec sessions alternating daily with variable-interval 30-sec sessions, while the second group was treated like the first on variable-interval days and yoked with the first as before on differential-reinforcement-of-other-behavior days. In both phases, response-decrement was more rapid and more marked in the differential-reinforcement-of-other-behavior animals than in the controls. The difference was due, at least in large measure, to sustainment of response in the control animals by adventitious reinforcement. All the differential-reinforcement-of-other-behavior animals developed “other” behavior—the same distinctive pattern of waiting at the foodcup—but there was no direct evidence that it contributed in any way to the decrement in lever pressing.     

COMPARISON OF EXTINCTION,DRO 0-SEC,AND DRO 6-SEC IN THE ELIMINATION OF IMITATIVE RESPONDING UNDER DISCRETE-TRIAL PARADIGMS1

Imitative response levels were observed for normal 5-yr-old children within a discrete-trial imitation paradigm. Following imitation training sessions, children were observed under conditions of contingent reinforcement for three experimental sessions. Following the contingent reinforcement phase, children were then observed under reversal conditions for four sessions. A 3 × 4 repeated measures design was employed for observing response decrements under conditions of extinction, DRO 6-sec, and DRO 0-sec. The DRO 0-sec group demonstrated a significantly greater decrement in imitative responding than did the DRO 6-sec and extinction group. The differences in effects between the two DRO conditions and results from previous studies in which DRO procedures have had little effect in reducing imitative responding, suggest an incomplete understanding of the ways in which DRO procedures may operate.     

Polydipsia's contribution to temporal discrimination of rats on a fixed interval schedule

This experiment concerned the contribution of polydipsia on the temporal discrimination of rats during a fixed-interval 60-sec. schedule. In this study, the timing accuracy of 12 rats which had access to water during training was compared to that of 12 rats which had no water during training. The rats were trained for 25 sessions on an FI 60-sec. schedule. In early sessions before polydipsia was fully developed, no differences existed between the timing accuracy of the water group and no-water group. As the amount of water drunk by the water group increased as the number of sessions increased, a parallel increase was noted in the timing accuracy of the water group. In the final sessions, a significant difference was found between the timing accuracy of rats in the water group and that of those in the no-water group. It was concluded that polydipsia facilitated the development of the temporal discrimination which is characteristic of a fixed-interval 60-sec. schedule.     

Behaviour of ‘impulsive’ and ‘non-impulsive’ humans in a temporal differentiation schedule of reinforcement

The operant behaviour of psychometrically defined ‘impulsive’ and ‘non-impulsive’ subjects, under a temporal differentiation schedule of reinforcement, was examined. Four impulsive and four non-impulsive females were selected on the basis of their scores on the Matching Familiar Figures Test. The subjects participated in fifteen 45-min sessions in which they were exposed to an inter-response-time-greater-than-10-sec schedule of monetary reinforcement. During Phase I (sessions 1–5) no information was provided about the reinforcement contingency. During Phase II (sessions 6–10) a light on the response panel was illuminated whenever a reinforcer became available. At the start of Phase III (session 11) the subjects were given explicit information about the reinforcement contingency. At the start of Phase IV (sessions 12–15) the subjects were told that the light would no longer be operative although the contingency would remain unaltered. During Phase I the impulsive subjects earned fewer reinforcers, and emitted a greater proportion of non-reinforced responses (inter-response times less than 10 sec) than the non-impulsive subjects. During Phase II both groups increased their earnings, although the performance of the non-impulsive group remained superior to that of the impulsive group. In Phase III both groups performed equally well. In Phase IV the performance of both groups deteriorated, the impulsive group performing more poorly than the non-impulsive group. The results demonstrate the sensitivity of operant performance maintained under temporal differentiation schedules to personality dimensions such as ‘impulsiveness/non-impulsiveness’.     

An experimental analysis of impulsivity and impulse control in humans

In choosing between small, immediate and large, delayed reward, an organism behaves impulsively if it chooses the small reward and shows impulse control if it chooses the large reward. Work with nonhumans suggests that impulsivity and impulse control may be derived from gradients of delayed reinforcement. A model developed by Ainslie and by Rachlin suggests that preference for the rewards should be a function of when the choice is made: small reward with no delay may be preferred to large reward with delay X, but adding delay T to both alternatives should shift preference to the large reward. Three experiments investigated this preference reversal in humans, using termination of 90 dba white noise as the reinforcing event. Experiment 1 showed that under some instructional conditions 90-sec noise off with no delay was preferred over 120-sec noise off after a 60-sec delay, but that preference shifted to the large reward when a 15-sec delay (T) was added to both alternatives. Experiment 2 replicated this preference reversal under two conditions of large, delayed reward, and with three rather than two values of T. Experiment 3 confirmed this effect of T and showed that some humans committed themselves to the large reward when commitment could be made some time before presentation of the reward alternatives. These data support the Ainslie-Rachlin model and extend it to human choice behavior.     

Nicotine trained as a negative feature passes the retardation-of-acquisition and summation tests of a conditioned inhibitor

Nicotine functions as a negative feature in a Pavlovian discriminated goal-tracking task. Whether withholding of responding to the conditional stimulus (CS) reflects nicotine functioning as a conditioned inhibitor is unknown. Accordingly, the present research sought to determine whether nicotine trained as a negative feature passed the retardation-of-acquisition and summation tests, thus characterizing it as a pharmacological (interoceptive) conditioned inhibitor. In the retardation test, rats received either nicotine (0.4 mg/kg) or chlordiazepoxide (5 mg/kg) negative feature training in which the drug state signaled when a 15-sec light CS would not be paired with sucrose; light was paired with sucrose on intermixed saline sessions. Following acquisition of the discrimination, both groups received nicotine CS training in which sucrose was intermittently available on nicotine but not intermixed saline sessions. Acquisition of conditioned responding to the nicotine CS was slower in the nicotine negative feature group than in the chlordiazepoxide negative feature group. In the summation test, rats were assigned to either the nicotine negative feature group or a pseudoconditioning control. In this control, the light CS was paired with sucrose on half the nicotine and half the saline sessions. Both groups also received excitatory training in which a white noise CS was paired with sucrose. The summation test consisted of presenting the white noise in conjunction with nicotine. Conditioned responding evoked by the white noise was decreased in the negative feature but not the pseudoconditioning group. Combined, the results provide the first evidence that an interoceptive stimulus (nicotine) can become a conditioned inhibitor.     

Intermittency in presentation increases identification of masked figures

Since low luminance nonsense figures projected onto visual noise tend to fade after onset, three groups of Os were used to determine if intermittency would aid pattern identification under such conditions. For the control group, patterns were superimposed on the noise for 5 sec. For the two experimental groups, an episcotister blade interrupted the patterns at rates of 2 and 8 Hz during the 5-sec presentation. Intermittency significantly increased the number of patterns correctly identified, but there was no difference between the two rates.     

Behavioral thermoregulation with microwave radiation of albino rats

The objective of this exploratory study was to investigate the extent to which microwave radiation would reinforce operant behavior in a cold environment. A reversal-design with the single subject serving as its own control was used for testing the reinforcing properties of microwaves. Six albino rats were conditioned to produce 6-sec. pulses of microwave radiation within a refrigerated environment. The schedule of reinforcement was continuous (crf). Each lever press produced a 6-sec. output of microwave radiation. The intensity of radiation was varied across blocks of sessions in the reversal design. Microwave values used were as follows: 62.5 W, 125 W, 250 W, and 437.5 W. Sessions lasted from 8 to 9 hr. over an approximate 7-mo. period. Results showed that rates of operant responding varied as a direct function of microwave intensity. Relatively high mean rates were associated with moderate microwave intensity (250 W), whereas lower mean rates of responding were associated with extreme microwave intensities (62.5 W and 437.5 W) in the reversal design. These data are explained in terms of satiation and deprivation of the reinforcing value of microwave radiation.     

Conditioned suppression and conditioned enhancement with the same positive UCS: an effect of CS duration

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.     

Stimulus intrusion on fixed-interval responding in the rat: The effects of electric shock intensity,temporal location,and response contingency

After a scalloped lever-press response pattern had developed under a fixed-interval food reinforcement schedule, a 15-sec electric shock was intruded for different groups of rats in the first, second, third, or fourth quarter of each inter-reinforcement interval. Shock intensity was systematically increased for individual rats over 70 sessions, from 0.05 to 1.6 mA. Additional between-groups comparisons involved response-dependent versus clock-dependent fixed-interval schedules, and response-dependent versus response-independent electric shock intrusion. Response rates within each fixed interval prior to, during, and following electric shock intrusion showed regular and reproducible increases and decreases under systematic application of the experimental variables. These results provide further evidence that the functions of a stimulus are determined in part by the parameters of intensity, response contingency, and temporal location with respect to reinforcement.     

Multiple fixed-interval schedules: transient contrast and temporal inhibition

Pigeons were exposed to four cycles per session of a multiple schedule in which each cycle involved twelve 60-sec fixed intervals followed by four 180-sec intervals [(12 FI 60-sec)(4 FI 180-sec) schedule]. Post-reinforcement pauses were shorter during the first few short intervals of each cycle than during later short intervals, and increased over the four long intervals of each cycle (positive and negative transient contrast). A (12 FI 15-sec)(4 FI 45-sec) schedule showed similar results. These two schedules differed in some other respects indicating effects of absolute FI duration on stimulus control. Differences in contrast properties between both these procedures and multiple variable-interval schedules were related to the pause-producing property of reinforcement on FI (temporal inhibition). Behavior under two other multiple fixed-interval schedules—(2 FI 360-sec)(1 FI 720-sec) and (3 FI 360-sec)(1 FI 720-sec)—differed in certain respects from both the (12 FI x-sec)(4 FI 3x-sec) schedules. These differences may be related to differences in the number of successive fixed intervals within a component (run length).     

Open versus closed economies: performance of domestic hens under fixed ratio schedules

Domestic hens responded under fixed-ratio schedules of food (wheat) reinforcement under several experimental conditions. Part 1 (open economy) investigated performance on fixed-ratio schedules over both multisession steady-state conditions and daily changes of the schedule, with hens maintained at 80% of free-feeding weights by extraexperimental feeding. In Parts 2 and 3 (closed economy and short sessions) sessions were 40 min long, and the hens' weights were allowed to vary (Part 2) or sessions were conducted only when the hens were at approximately 80% of free-feeding weights (Part 3). In Part 4 (closed economy and long sessions) sessions were 24 hr long and the fixed-ratio requirement was changed either daily or after 7 consecutive days. In general, the daily changes of fixed-ratio requirement in the open economy and short-session closed economy gave much the same result as the steady-state open-economy sessions. Overall response and reinforcer rates decreased with increasing fixed-ratio requirement (except at the shortest fixed ratios). Running response rates decreased, and postreinforcement pauses generally increased. In contrast, overall response rates in the long-session closed economy generally increased with the fixed-ratio requirement. Session length is suggested as a cause of the differences between the short- and long-session closed-economy results.     

Disruption of a temporal discrimination under response-independent shock

The responding of rats was reinforced on one key after a 1-sec auditory stimulus and on a second key after a 5-sec stimulus. With errors punished by a short timeout, all subjects achieved a high level of accuracy. A chain of responses during the stimuli mediated the performance so that when the auditory signals were omitted accuracy decreased only slightly. Response-independent aversive stimulation superimposed upon this procedure both suppressed the total amount of behavior and reduced the accuracy of the discriminative performance, the intensity of the stimulus determining the error rate. The increase in errors under these conditions may have depended in part upon differential suppression of members of the response chain, but such suppression was not necessary, since error rate increased even in its absence. Furthermore, the locus of response disruption within the chain was not consistent from day to day either for any individual animal or across animals.     

Auditory masking-level differences in the cat.

Four cats were trained to avoid shock by responding to the intermittent occurrence of 1-kHz tone pulses at one ear, while a continual train of noise pulses was simultaneously presented either to the signal ear alone or to both ears. Using the masked threshold levels determined with monaural noise as a reference, the amount of unmasking produced by the addition of noise to the nonsignal ear was measured. Significantly lower tonal detection thresholds were observed when noise equal in intensity to that at the signal ear was added to the nonsignal ear. Additional unmasking occurred when the intensity of the noise at the latter ear was raised to a level 10 db. higher than that at the signal ear.     

Temporally spaced responding by pigeons: development and effects of deprivation and extinction

In the first five or six sessions on a DRL 20-sec schedule of reinforcement there developed a stable performance characterized by a relatively constant conditional probability of occurrence (IRTs/op) of interresponse times (IRTs) of durations greater than 5 or 6 sec. Extinction and the level of deprivation changed both the overall rate of responding and the form of the function relating the duration of an IRT to its value of IRTs/op. The value of IRTs/op decreased more rapidly for short than for longer IRTs, resulting in the emergence of a finer discrimination of IRT duration.     

The effects of number of responses on the postreinforcement pause in fixed-interval schedules

The present study manipulated the number of responses in a modified fixed-interval schedule by imposing a blackout after each unreinforced response during the interval. The blackout duration was varied, and the duration of the fixed interval was held constant. The subjects were initially exposed to a fixed-interval 300-sec schedule. Blackout durations of 0, 10, and 50 sec were used. Following this, a fixed-interval 30-sec schedule was used with blackout durations of 0, 1, and 5 sec. Under the fixed-interval 300-sec schedule, the number of interreinforcement responses varied over a wider range than occurred under the fixed-interval 30-sec schedule. The duration of the postreinforcement pause decreased as blackout durations were increased and number of responses decreased on the fixed-interval 300-sec schedule, but pause length did not vary with changes in blackout duration and number of responses for the fixed-interval 30-sec schedule. The differences in the effects of blackout duration and response manipulation on the two fixed-interval schedules were attributed to relatively greater changes in the number of interreinforcement responses for the fixed-interval 300-sec schedule.     

The impact of variation and autonomy on psychological responses to high intensity interval training exercise

IntroductionHigh-intensity interval training (HIIT) provides notable physiological benefits and is generally well-tolerated across modalities and populations. This study investigated how exercise autonomy support impacts psychological responses to exercise.MethodsTwenty-nine participants completed three HIIT trials: Conventional-HIIT with 60-sec work segments, Varied-HIIT with a mix of 30, 60, 90, & 120-sec segments, and Autonomous-HIIT with self-selected 30, 60, 90, & 120-sec segments. Affective valence, enjoyment, and intention were measured.ResultsAffective valence during exercise was not different between trials (p > 0.05) but enjoyment during exercise was higher for Autonomous-HIIT (p < 0.05). Enjoyment and intention measured post-exercise were greater for Autonomous-HIIT than Varied-HIIT (p < 0.05).ConclusionAutonomous HIIT produced more desirable responses than varied and traditional HIIT sessions. These data suggest that HIIT sessions utilizing self-selected interval durations can produce more positive responses, which provides the basis for recommending autonomy within HIIT exercise.     

Activation of Locations in Working Memory in Cats

Cats saw an object appear and disappear at two successive locations; the movement of the object from one location to the other was not perceived but was indicated by indirect cues and the two disappearances were separated by a 0-sec or a 20-sec interval. Performance was poorer with the 0-sec than with the 20-sec interval. With the 0-sec interval, the percentages of search attempts made at the object's initial and final hiding locations did not differ whereas with the 20-sec interval, more search attempts were made at the final than at the initial location. These results provide additional support to Goulet, Dore and Rousseau's (1994) interpretation of cats' search behaviour in terms of activation of spatial locations in working memory.     

Brightness exponent as a function of retinal eccentricity in the peripheral visual field: Effects of dark and light adaptation

Using a method of direct magnitude estimation, the exponent of the brightness power function was determined under dark and light adaptation at luminance levels well above threshold. The exponent was estimated for functions describing the brightness of stimuli presented at the fovea and the following peripheral retinal loci: 10, 20, 30, 40, and 50 deg nasally eccentric to the fovea along the horizontal meridian of the right eye. The exponent for a 1-sec flash was found to be approximately .33 at the fovea and increased slightly with increasing retinal eccentricity.The effect of adaptation on the brightness exponent was not so large when the target luminance was set well above threshold.     

Effects of ambient noise on time estimation by humans

10 male and 10 female undergraduates were asked to estimate 5-, 10-, 15-, and 30-sec. intervals under five intensities of ambient noise (50, 60, 70, 80, and 90 dB). Interval estimates became shorter as the intensity of noise increased from 50 to 80 dB but became longer at 90 dB. The effects of intensity of noise were most prominant in the two longest intervals. These results are interpreted in terms of CNS arousal theory.