Response-independent Schedule Research Articles

POSITIVE CONDITIONED SUPPRESSION: AN EXPLANATION IN TERMS OF MULTIPLE AND CONCURRENT SCHEDULES1

Rats performed under a baseline variable-interval schedule of food presentation. A response-independent food schedule was then superimposed on the baseline schedule for different periods of time across different conditions. The response-independent schedule operated for the whole session in some conditions, intermittently for sixty second periods in some, and intermittently for ten-second periods in others. Under these latter two sets of conditions, the response-independent food schedule was stimulus correlated and alternated with the baseline schedule according to a multiple schedule. Response-independent food presentations always suppressed responding. The degree of suppression tended to increase the longer the period of response-independent food. Control conditions, in which the superimposed schedule was response-dependent, rather than response-independent, did not produce response suppression. The results fit an analysis of positive conditioned suppression phenomena in the context of multiple and concurrent schedule effects.

The effect of a response requirement on schedule-induced aggression

The attack behavior induced in pigeons by a fixed-ratio schedule of food reinforcement was compared with that induced by a variable-time schedule composed of the actual interreinforcement intervals of the preceding fixed-ratio schedule condition. For two of the four pigeons that exhibited schedule-induced aggression against a nearby stuffed pigeon, the response-dependent (fixed-ratio) schedule induced a higher rate of attack than did the response-independent (variable-time) schedule. For the remaining two birds, no measure of induced aggression was consistently related to either schedule condition. These results indicate that a response requirement for reinforcement is not a limiting condition for the induction of attack behavior in pigeons.

Combined stimulus control over time allocation in response-independent schedules

Rats were exposed to concurrent schedules in which reinforcers occurred independently of behavior. In Experiment 1, rats could control time spent in the following conditions: (1) a light, (2) white noise, and (3) the absence of both light and noise. Response-independent reinforcers occurred at the same rate during the light and the noise and at either a higher rate or not at all in the absence of both stimuli. In subsequent tests, the rats spent more time in a light and noise compound than in either light or noise alone after the absence of both stimuli had signaled no reinforcers. When the absence of both stimuli had signaled a higher rate of reinforcement, however, the rats typically spent less time in the compound than in light or noise alone. In Experiment 2, rats could control time spent in the presence of a light and of a buzzer. The reinforcement rate in the light was twice that in the buzzer. In a later test, the rats spent more time in a light and buzzer compound than in the buzzer, but less time in the compound than in the light. The results show that additive summation, suppressive summation, and stimulus averaging of time allocation occur and that response rate differences between training stimuli are not necessary for these phenomena.

Reinforcement omission and schedule-induced drinking in a response-independent schedule in rats

Drinking, food-cup contact, exploration, and grooming were analysed in two food-deprived rats when food pellets were delivered on a fixed-time (FT) schedule of 1 min. The probability of drinking was high immediately after pellet delivery and then decreased to zero with the gradual increase in the probability of food-cup contact, exploration, and grooming. The probability of grooming decreased and the probability of food-cup contact and exploration increased when drinking was absent after occasional feeder operations without pellet delivery (reinforcement omission). This omission effect upon food-cup contact and exploration responses was experimentally simulated by preventing the drinking burst after ordinary pellet delivery.

ELIMINATION OF REINFORCED BEHAVIOR: INTERMITTENT SCHEDULES OF NOT‐RESPONDING1

Pigeons' key pecking resulted in food according to either a variable-ratio or a variable-interval schedule. At the same time, food was available for not pecking for a specified time. The required time of not-pecking was segmented into not-responding units, and these units were followed by food according to a fixed-ratio schedule. Both unit duration and the number required were varied. In general, the shorter the time unit or the smaller the ratio, the lower was response rate. When total required not-responding time was constant, but changes in unit duration and the number required altered how the total was achieved, shorter units produced lower rates. Other conditions involved substitution of food delivered independent of responding for the not-responding schedule. With low and moderate total times to food presentation, the not-responding schedule produced lower rates; with the longest times, the response-independent schedule generated less responding. When considered in terms of relative frequency of food presentation available from a source other than pecking, the not-responding schedule reduced rate more effectively than did the response-independent schedule. Comparisons with other research suggested that food presented dependent on not responding compared favorably with punishment as a procedure for reducing response rate. Transient effects differed. Although punishment temporarily depresses rate when first imposed and temporarily enhances it when first removed, food given for not responding quickly generated steady-state rates.

POSITIVE REINFORCEMENT AND THE ELIMINATION OF REINFORCED RESPONSES1

Key pecking was maintained on a fixed-interval schedule while either a differential-reinforcement-of-not-responding or a fixed-time schedule was imposed simultaneously. The lower the time parameter of the not-responding schedule, the lower was the response rate. Similar effects occurred with the fixed-time schedule, if the pigeons had experience with reinforcement for not responding. Otherwise the effects were less orderly, to the extent that rate could reach maximum with the lowest-valued fixed-time schedule. The not-responding and the response-independent schedules had similar effects on rate in experienced pigeons only when the time parameter or nominal frequency of food presentation was considered. When considered in terms of obtained frequency of food presentation, reinforcement of not responding produced larger decrements in rate than did the fixed-time schedule.

Some factors controlling the interaction between response-dependent and response-independent schedules of reinforcement

Response rate interactions were studied in four rats following a shift from: (a) a multiple schedule in which two stimuli, S1 and S2, were both correlated with response-dependent reinforcement (mult VI 1 min VI 1 min) to (b) a multiple schedule in which S2 was now correlated with response-independent reinforcement (mult VI 1 min VT 1 min). Concomitant with the decrease in the rate of responding in the VT component, there was also a decrease in rate of responding during the VI component, i.e., negative induction. The nature of the observed interaction suggested that responding appropriate to the VT component may have generalized to the VI component. To test this interpretation, in a second experiment an effort was made to accentuate the differences between the components of the multiple schedules and consequently to reduce the degree of interaction. For four rats, two had a different reinforcer correlated with each component and two had a different response lever correlated with each component. The results of the separate-reinforcer treatment were not consistently different from those results obtained in Experiment I. The separate-lever treatment, however, resulted in decreased negative induction interaction and lower rates of responding during the VT component.

Operant GSR conditioning with cool air reinforcement.

Two groups of 20 Ss each run individually in a soundproff chamber heated to 115 F and humidified to 100%. Ss in the experimental group received brief presentation of cool air contingent upon wmitted GSRs during 20 min of acquisition. Control Ss were matched on at a time in operant rate and were yoked one at a time to receive the cool air on a response-independent schedule. Both groups increased significantly in rate of unelicited GSRs during acquisition, with the experimental Ss' curve rising more rapidly and both groups attaining equivalent terminal levels. During extinction, the groups maintained high levels of responding and did not differ. Examination of basal skin conductance data ruled our an activation hypothesis. In the control Ss, terminal response frequency was significantly correlated with percentage of fortuitous response-contigent reinforcement. It was concluded that both croups were conditioned, with the controls receiving intermittent reinforcement sufficiently often to elevate their responding. The cool air was judged to be an effective reinforcer of unelicited GSRs, perhaps more effective than those used in previous studies.

PREFERENCE AND DISCRIMINATION BETWEEN RESPONSE‐DEPENDENT AND RESPONSE‐INDEPENDENT SCHEDULES OF REINFORCEMENT1

Four Asian quail (Coturnix coturnix japonica) were exposed to concurrent-chain schedules, the terminal links of which were either variable-interval 30 sec and variable-time 30 sec, or fixed-interval 30 sec and fixed-time 30 sec. Except for one bird that exhibited a preference for the variable-interval schedule over the variable-time schedule, no consistent preferences were demonstrated for response-dependent or response-independent schedules. However, response rates were three times greater on response-dependent than on response-independent schedules. The discrimination between terminal-link schedules was rapidly recovered after the schedule positions were reversed. Casual observations revealed that the birds engaged in stereotypic circling and pecking while the response-independent schedules were operative.

CHOICE AND RESPONSE CONTINGENCIES1

Two experiments investigated the extent to which response contingencies influence the choice between two schedules of reinforcement by exposing pigeons to a concurrent-chains procedure in which reinforcers in one terminal link were response-independent, and in the other terminal link, response-dependent. In Experiment 1, the pigeons were indifferent between an aperiodic, response-independent schedule and an aperiodic, response-dependent schedule that required a minimum rate of responding. This finding limits the generality of a required-rate contingency as a determinant of choice, which contingency had been previously demonstrated in a context of periodic reinforcement to evoke preference for an alternate schedule. In Experiment 2, the pigeons preferred a periodic, response-independent schedule to a periodic, response-dependent schedule that shared a feature with a required-rate schedule: there was a requirement to respond early in the interreinforcement interval, when responding produced reinforcement only later. The results of the two experiments suggest the following general interpretation: pigeons prefer a second schedule to the extent that the response contingencies of the first schedule must be satisfied during discriminable periods of nonreinforcement.

Disinhibition and spontaneous recovery of response decrements produced by free reinforcement in rats.

Spontaneous recovery and disinhibition were studied in 3 experiments in which, after rats had been trained to bar press on a variable interval schedule of reinforcement, response rates were reduced by the introduction either of extinction or of a response-independent (free) reinforcement schedule. Spontaneous recovery was consistently obtained in extinction, especially when session durations were long. Under free reinforcement conditions there was little sign of spontaneous recovery, even when with high reinforcement rates response reduction was almost as rapid as in extinction. In disinhibition tests the introduction of noise produced increased responding under free reinforcement conditions, but not in extinction. The results are interpreted as demonstrating a dissociation between spontaneous recovery and disinhibition.

Do rats like to work for their food?

Rats were given a choice in a two-compartment box between response-dependent and response-independent schedules of food presentation. In general, the response-independent schedule was preferred, but the preference was not exclusive and considerable amounts of time were spent on the “work” (response-dependent) side. Food deprivation caused an increased preference for the response-independent schedule when the schedules were fixed, but not when they were variable. Addition of a signal to the work side, indicating the availability of reinforcement, increased preference for that side. In general, the relative numbers of reinforcements obtained on the response-independent side exceeded the relative time spent there; when the relative reinforcements were equated by adding delays to the response-independent side, indifference between the schedules resulted. Latencies of food collection were higher on the response-independent side than on the lever side, and it is suggested that this gives a clue to the factors maintaining “work” in this situation.

Effects of Lever-Press-Dependent and Independent Electric Shock on Schedule-Induced Water Intake

Fixed-interval 300-sec. electric shock of sufficient intensity to suppress lever pressing in rats responding under a fixed-ratio-30 food schedule led to an increase in schedule-induced water intake (Experiments 1 and 2). In Experiment 3 response-independent electric shock delivered under a variable-time 180 sec. schedule and which occurred simultaneously with the delivery of a food pellet attenuated post-pellet water intake in rats receiving food pellets under a fixed-time 40-sec. food schedule. In Experiment 4 shock also was delivered under a variable-time 180-sec. schedule but was not delivered simultaneously with food pellets. Even though it was unlikely that shocks were administered while S was drinking, attenuation of post-pellet drinking during shock was observed in an animal receiving food pellet according to a response-independent schedule.

DISCRIMINATION OF A RESPONSE‐INDEPENDENT COMPONENT IN A MULTIPLE SCHEDULE1

Pigeons were trained to respond in non-differential reinforcement pre-discrimination training, with a multiple variable-interval 1-min variable-interval 1-min schedule. Each bird then received discrimination training with a multiple variable-interval 1-min variable-time 1-min schedule. Thus, discrimination training was between response-dependent (variable-interval) and response-independent (variable-time) schedules with the rate of reinforcement equated. In Experiment I, only three sessions of non-differential reinforcement preceded discrimination training and for half the birds, a 0 degrees line was correlated with the response-dependent schedule; for the remaining birds the 0 degrees line was correlated with the response-independent schedule. Post-discrimination gradients of excitatory stimulus control were obtained from the former group, while the latter group showed little evidence of post-discrimination stimulus control by the 0 degrees line. Differential responding to the variable-time schedule was not accompanied by behavioral contrast to the variable-interval schedule. In Experiment II, 20 sessions of non-differential reinforcement preceded discrimination training and the 0 degrees line was correlated with variable-time reinforcement for each bird. Differential responding to the 0 degrees line was accompanied by negative induction to the variable-interval schedule and by inhibitory stimulus control about the 0 degrees line during a post-discrimination generalization test.

The effects of signaled response-independent shocks on behavior under avoidance and extinction schedules

Response rates of rats were recorded during a 30-sec signal (CS) which preceded a response-independent electric shock when: (1) baseline avoidance shocks were withheld during the signal; (2) baseline avoidance shocks were available during the stimulus; and (3) baseline avoidance shocks were withheld but a response-independent shock was intruded on each trial at the midpoint of the signal. Two different adjusting avoidance baselines were used. The data suggest that the signal suppresses responding, but also that this effect can be overcome by shocks supplied either from the baseline schedule or intruded on a response-independent schedule.

CONCURRENT SCHEDULES OF RESPONSE‐INDEPENDENT REINFORCEMENT: DURATION OF A REINFORCING STIMULUS

Presentations of grain to three pigeons were determined by two response-independent schedules. Interpresentation intervals varied with a mean interval of 1.5 min for each schedule. Both were concurrently operative, but grain was presented by one only when the chamber was illuminated with blue light and by the other only during amber illumination. A response on a white key, the only key in the chamber, alternated the stimulus conditions and the effective schedule. Grain presentation durations associated with the illumination conditions were varied from 1.5 to 4.5 sec. The proportion of the total session time spent in an illumination condition closely approximated the relative grain presentation duration provided in that illumination. For two of the birds, the proportion of the total number of grain presentations obtained in an illumination condition was an increasng function of the presentation duration in that illumination.

Instrumental and Motivationally Induced Drinking under Dry Food Reinforcement Schedules

2 experiments were conducted in which rats were exposed to a succession of response-independent and lick-contingent dry food reinforcement schedules with water freely available. The two experiments differed solely with regard to the preferability of a second solution which was made freely and concurrently available with the water. Differences in the rate and topography of pre- and post-pellet water drinking, as well as the transfer of post-pellet drinking from water to a highly preferred solution suggested that post-pellet drinking was under the control of motivational factors and only pre-pellet licking was under the control of the reinforcement contingency.

Fixed and variable schedules of response-independent reinforcement.

After response-dependent reinforcement established key-pecking as the predominant response, pigeons received schedules in which reinforcements occurred without reference to responding. These response-independent schedules involved either a reinforcement every 5 min, or reinforcements at irregular intervals that averaged 5 min. The response-independent schedules generated characteristic patterns of responding. The fixed schedule produced positively accelerated responding between reinforcements, and the variable schedule produced either steady rates, erratic, or negatively accelerated patterns. The patterns developed independent of the distribution of responses existing when the schedule was first imposed. The rate of responding varied for the three birds, but, for all, response-independent schedules decreased the rates below the level maintained by response-dependent reinforcement. Although the rate of responding was affected primarily by the events contiguous with reinforcement, the pattern of responding appeared to be determined mainly by the presentation of reinforcements in relation to time.