Response induction during the acquisition and maintenance of lever pressing with delayed reinforcement

The acquisition of lever pressing by rats and the occurrence of unreinforced presses at a location different from that of the reinforced response were studied using different delays of reinforcement. An experimental chamber containing seven identical adjoining levers was used. Only presses on the central (operative) lever produced food pellets. Groups of 3 rats were exposed to one of seven different tandem random-interval (RI) fixed-time (FT) schedules. The average RI duration was the complement of the FT duration such that their sum yielded a nominal 32-s interreinforcement interval on average. Response rate on the operative lever decreased as the FT value was lengthened. The spatial distribution of responses on the seven levers converged on the operative lever when the FT was 0 or 2 s and spread across the seven levers as the FT value was lengthened to 16 or 32 s. Presses on the seven levers were infrequent during the FT schedule. Both operative- and inoperative-lever pressing intertwined in repetitive patterns that were consistent within subjects but differed between subjects. These findings suggest that reinforcer delay determined the response-induction gradient.     

Bouts of responding from variable-interval reinforcement of lever pressing by rats

Four rats obtained food pellets by lever pressing. A variable-interval reinforcement schedule assigned reinforcers on average every 2 min during one block of 20 sessions and on average every 8 min during another block. Also, at each variable-interval duration, a block of sessions was conducted with a schedule that imposed a variable-ratio 4 response requirement after each variable interval (i.e., a tandem variable-time variable-ratio 4 schedule). The total rate of lever pressing increased as a function of the rate of reinforcement and as a result of imposing the variable-ratio requirement. Analysis of log survivor plots of interresponse times indicated that lever pressing occurred in bouts that were separated by pauses. Increasing the rate of reinforcement increased total response rate by increasing the rate of initiating bouts and, less reliably, by lengthening bouts. Imposing the variable-ratio component increased response rate mainly by lengthening bouts. This pattern of results is similar to that reported previously with key poking as the response. Also, response rates within bouts were relatively insensitive to either variable.     

Avoidance conditioning with shock contingent upon the avoidance response

Rats learned either a lever-press response, a shuttle response or a one-way crossing response, which produced one immediate shock but was instrumental in avoiding five identical shocks scheduled to occur later. These responses were acquired both with and without support of an escape contingency. These results support shock-frequency reduction as a sufficient condition for the acquisition and maintenance of avoidance.     

Response cost effects during extinction following fixed-interval reinforcement in humans

This study examined the effects of response-produced cost upon human observer responses during extinction following FI reinforcement. Relative to a no-cost condition, cost produced marked and rapid response attenuation.     

Stimulus control of responding during a fixed-interval reinforcement schedule

During training sessions, pecks by pigeons on a response key illuminated by a vertical line of white light resulted in reinforcement and an ensuing blackout according to a fixed-interval schedule. Training sessions were followed by dimensional stimulus control test sessions during which the orientation of the line present throughout the fixed interval was varied. Inverted U-shaped (excitatory) gradients of responding, with maximum responding occurring in the presence of the vertical line, were observed during the terminal part of the fixed interval. U-shaped (inhibitory) gradients of responding, with minimum responding occurring in the presence of the vertical line, were observed during the early part of the fixed interval when the preceding interval had terminated with reinforcement and blackout but not when the preceding interval had terminated with blackout only. These results suggest that the dimensional control by the stimulus present throughout the fixed interval is of a conditional variety. Whether the fixed-interval stimulus exerts inhibitory or excitatory dimensional control depends upon the presence and absence, respectively, of stimuli associated with reinforcement.     

Signaled reinforcement effects on fixed-interval performance of rats with lever depressing or releasing as a target response

The effect of a diffuse auditory signal filling a brief delay between a response and reinforcement depends upon the nature of the trained target response. Rats in a signaled condition responded slower than rats in an unsignaled condition if the target response was lever release. If the target response was lever depression, however, rats in the signaled condition responded faster than rats in the unsignaled condition at the end of training     

Continuous, fixed-ratio, and fixed-interval reinforcement in honey bees

Bees learned to enter a Plexiglas tube and to suck small portions of sugar solution; every entry or every fifth entry was reinforced. During an extinction phase, the bees on the fixed-ratio schedule emitted twice as many responses as did those given continuous reinforcement. Bees on a fixed-interval schedule of reinforcement emitted lower response rates than did those given fixed-ratio reinforcement. By extending the conditioning procedure for several days, it was possible to maintain responding with fixed-ratio schedules requiring 30 responses per reinforcement and with fixed-interval values up to 90 sec. Under fixed-interval schedules, response rates did not increase toward the end of the reinforcement intervals.     

Effects of reinforcement rate and delay on the acquisition of lever pressing by rats.

The acquisition of lever pressing by naive rats, in the absence of shaping, was studied as a function of different rates and unsignaled delays of reinforcement. Groups of 3 rats were each exposed to tandem schedules that differed in either the first or the second component. First-component schedules were either continuous reinforcement or random-interval 15, 30, 60 or 120 s; second-component schedules were fixed-time 0, 1, 3, 6, 12, or 24 s. Rate of responding was low under continuous immediate reinforcement and higher under random-interval 15 s. Random interval 30-s and 60-s schedules produced lower rates that were similar to each other. Random-interval 120 s controlled the lowest rate in the immediate-reinforcement condition. Adding a constant 12-s delay to each of the first-component schedule parameters controlled lower response rates that did not vary systematically with reinforcement rate. The continuous and random-interval 60-s schedules of immediate reinforcement controlled higher global and first-component response rates than did the same schedules combined with longer delays, and first-component rates showed some graded effects of delay duration. In addition, the same schedules controlled higher second-component response rates in combination with a 1-s delay than in combination with longer delays. These results were related to those from previous studies on acquisition with delayed reinforcement as well as to those from similar reinforcement procedures used during steady-state responding.     

Response-duration of lever pressing in the rat

Two aspects of the lever-holding behaviour of rats in a Skinner-box have been analysed: firstly, the changes in the duration of the responses during the acquisition and experimental extinction phase, and, secondly, the bunching of responses during the experimental extinction phase. The response-durations on the first few acquisition trials were found to be bimodally distributed, but to become stabilized at 0.42 seconds as practice increased. During experimental extinction response-durations increased. The rate of increase depended on the conditions of secondary reward. Rats who had the source of secondary reward removed, or restricted, yielded a steeper slope than those who responded under the same conditions of secondary reward as during training.

The analysis of the extinction scores revealed that unrewarded responses were emitted in groups. Response-group latencies were shown to progress as a positive function of the number of response-groups, and the average response-duration for consecutive response-groups to increase progressively. The slope of the duration curve plotted for successive response-groups increased, and this was related to an increase in the value of the time-intercept for successive response-groups.     

Contrast effects in multiple fixed-interval reinforcement schedules

Pigeons were exposed to a multiple fixed-interval one-minute fixed-interval three-minute schedule of reinforcement following training on either a multiple fixed-interval one-minute fixed-interval one-minute schedule or a multiple fixed-interval three-minute fixed-interval three-minute schedule. For all birds, large negative local contrast effects developed during the first of four three-minute intervals in a component; response rate was depressed and postreinforcement pause lengthened in this interval. Positive local contrast effects were evident during the first of 12 one-minute intervals in a component for five of six birds; at asymptote, the pause was very short and response rate slightly elevated during this interval. Overall positive contrast was generally transient and varied considerably across subjects, while overall negative contrast effects, if they occurred, appeared only after a large number of sessions.     

The effects of response contingent reinforcement and response contingent punishment upon the frequency of stuttered verbal behavior

Twelve adult subjects, 4 in each experimental condition, were exposed to 2 punishment contingencies and 1 punishment and reinforcement combined contingency, under a procedure of stimulus control. Results indicated all 3 conditions to be equally effective in the reduction of stuttering frequency. Spontaneous recovery during stimulus control segments was not observed following any of the three experimental contingencies. Implications for research and therapy are discussed.     

Development of behavioral compensation to the effects of scopolamine during fixed-interval reinforcement

Rats were injected with scopolamine before every daily session of water reinforcement on a fixed-interval (FI) schedule. Initially the drug decreased the rate of responding. Control injections of scopolamine following each session did not. Over 119 sessions, the typical FI performance developed more slowly in the animals drugged before the sessions. Their rates of responding increased from session to session, to a level slightly greater than that of the animals drugged after the sessions. Their rates did not increase. The effects of injections before the session were not duplicated by increasing the deprivation of animals drugged after the session.     

Order and chaos in fixed-interval schedules of reinforcement

Fixed-interval schedule performance is characterized by high levels of variability. Responding is absent at the onset of the interval and gradually increases in frequency until reinforcer delivery. Measures of behavior also vary drastically and unpredictably between successive intervals. Recent advances in the study of nonlinear dynamics have allowed researchers to study irregular and unpredictable behavior in a number of fields. This paper reviews several concepts and techniques from nonlinear dynamics and examines their utility in predicting the behavior of pigeons responding to a fixed-interval schedule of reinforcement. The analysis provided fairly accurate a priori accounts of response rates, accounting for 92.8% of the variance when predicting response rate 1 second in the future and 64% of the variance when predicting response rates for each second over the entire next interreinforcer interval. The nonlinear dynamics account suggests that even the “noisiest” behavior might be the product of purely deterministic mechanisms.     

Within-session changes in key and lever pressing for water during several multiple variable-interval schedules

Rats pressed keys or levers for water reinforcers delivered by several multiple variable-interval schedules. The programmed rate of reinforcement varied from 15 to 240 reinforcers per hour in different conditions. Responding usually increased and then decreased within experimental sessions. As for food reinforcers, the within-session changes in both lever and key pressing were smaller, peaked later, and were more symmetrical around the middle of the session for lower than for higher rates of reinforcement. When schedules provided high rates of reinforcement, some quantitative differences appeared in the within-session changes for lever and key pressing and for food and water. These results imply that basically similar factors produce within-session changes in responding for lever and key pressing and for food and water. The nature of the reinforcer and the choice of response can also influence the quantitative properties of within-session changes at high rates of reinforcement. Finally, the results show that the application of Herrnstein's (1970) equation to rates of responding averaged over the session requires careful consideration.     

The response-reinforcement dependency in fixed-interval schedules of reinforcement

Pigeons were exposed to four different schedules of food reinforcement that arranged a fixed minimum time interval between reinforcements (60 sec or 300 sec). The first was a standard fixed-interval schedule. The second was a schedule in which food was presented automatically at the end of the fixed time interval as long as a response had occurred earlier. The third and fourth schedules were identical to the first two except that the first response after reinforcement changed the color on the key. When the schedule required a peck after the interval elapsed, the response pattern consisted of a pause after reinforcement followed by responding at a high rate until reinforcement. When a response was not required after the termination of the interval, the pattern consisted of a pause after reinforcement, followed by responses and then by a subsequent pause until reinforcement. Having the first response after reinforcement change the color on the key had little effect on performance. Post-reinforcement pause duration varied with the minimum interreinforcement interval but was unaffected by whether or not a response was required after the interval elapsed.     

Competition between noncontingent and contingent reinforcement schedules during response acquisition

We examined the extent to which noncontingent reinforcement (NCR), when used as treatment to reduce problem behavior, might interfere with differential reinforcement contingencies designed to strengthen alternative behavior. After conducting a functional analysis to identify the reinforcers maintaining 2 participants' self-injurious behavior (SIB), we delivered those reinforcers under dense NCR schedules. We delivered the same reinforcers concurrently under differential-reinforcement-of-alternative-behavior (DRA) contingencies in an attempt to strengthen replacement behaviors (mands). Results showed that the NCR plus DRA intervention was associated with a decrease in SIB but little or no increase in appropriate mands. In a subsequent phase, when the NCR schedule was thinned while the DRA schedule remained unchanged, SIB remained low and mands increased. These results suggest that dense NCR schedules may alter establishing operations that result in not only suppression of problem behavior but also interference with the acquisition of appropriate behavior. Thus, the strengthening of socially appropriate behaviors as replacements for problem behavior during NCR interventions might best be achieved if the NCR schedule is first thinned.     

Development of key-pecking, pause, and ambulation during extended exposure to a fixed-interval schedule of reinforcement

Six pigeons key-pecked under a fixed-interval (FI) 3-min schedule of food presentation. Each pigeon was studied for 200 daily sessions with 15 intervals per session (3,000 total food presentations). Analyses included the examination of latency to first peck (pause), mean rate of key pecking, and ambulation. Characterizations of stable performance were assessed across measures of behavior and evaluated using commonly employed stability criteria. Stability of response rate and pause was identified better by assessments that evaluated variability and trend, rather than just variability. Between-subject differences in rate of acquisition and terminal values of steady-state performance of pause were observed, and stable pause durations took longer to develop than did stable key-pecking rates. Relative variability in response rate and pause duration decreased as the means increased. A temporally organized pattern of key-pecking (the so-called FI scallop) developed within 50 sessions of exposure to the schedule. Overall ambulation decreased during the early sessions of exposure and further analyses showed greater rates of ambulation during the pause than after it for 4 of the 6 pigeons. Performance under the FI 3-min schedule developed relatively slowly, and key-pecking, pause, and ambulation developed at different rates.