Josele Abreu-Rodrigues

Verbal Mediating Responses: Effects on Generalization of Say-Do Correspondence and Noncorrespondence.

We analyzed the effects of verbal mediating responses on the acquisition and generalization of say-do correspondence and noncorrespondence. Participants were assigned to groups in which either reinforcers (feedback and tokens) were arranged for say-do correspondence and noncorrespondence, or no reinforcers were programmed. Participants in these groups were further subdivided into groups in which they were required to repeat what was said previously, were required to repeat random numbers, or no verbalizations were required. When correspondence was reinforced, repetition of what was said produced greater acquisition and generalization of correspondence. When noncorrespondence was reinforced, repetition of numbers facilitated acquisition and generalization of noncorrespondence. Verbal mediating responses interacted with contingencies of reinforcement in determining acquisition and generalization of correspondence and noncorrespondence.

History effects on induced and operant variability.

Two experiments evaluated history effects on induced and operant variability. College students typed three-digit sequences on a computer keyboard. Sequence variability was induced (by no reinforcement or variation- independent reinforcement) or reinforced (by variation- or repetition-dependent reinforcement). Conditions with induced and operant variability were presented according to a reverse between-groups design. In Experiment 1, we examined transitions from the variation or repetition contingencies to no reinforcement, and vice versa. In Experiment 2, the variation or repetition contingencies were followed or preceded by variation-independent reinforcement. The results showed that (1) a history of no reinforcement impaired operant variability learning; (2) induced variability levels were higher and lower after a history of reinforcement for variation and repetition, respectively; (3) repetition was more easily disrupted by no reinforcement and independent reinforcement than was variation; and (4) response variability and stability were a function of past and current reinforcement conditions. These results indicate that reinforcement history influences both induced and operant variability levels.

Rules and Self-Rules: Effects of Variation Upon Behavioral Sensitivity to Change

Four experiments compared the effects of self-rules and rules, and varied and specific schedules of reinforcement. Participants were first exposed to either several schedules (varied groups) or to one schedule (specific groups) and either were asked to generate rules (self-rule groups), were provided rules (rule groups), or were not asked nor provided rules (control groups). When exposed to FI, sensitivity was greater for the varied than for the specific self-rules and rules groups, regardless of reinforcement rate. Control groups showed intermediate sensitivity levels. When nondifferentiated response rates were obtained, sensitivity for the varied groups was similar to that observed for the specific groups. These results suggest that varied rules promote greater sensitivity than do specific ones as long as variable behavior patterns are obtained.

Effects of Historical and Social Variables on Instruction Following

The present study investigated the effect of the presence of the experimenter on behavioral sensitivity to contingency change. In history training, college students were exposed to differential reinforcement of low rate (DRL) and fixed-ratio (FR) schedules, and in testing, to a fixed-interval (FI) schedule. For the control group, instructions were never provided, whereas for the without-observer and with-observer groups, inaccurate instructions were given (variable ratio [VR], fixed time [FT], and differential reinforcement of high rate [DRH], respectively). The experimenter was present during testing for the with-observer group. In history training, DRL response rates were lower than FR rates with or without instructions. In testing, the control and without-observer groups showed lower response rates and a more efficient behavioral patterning than did the with-observer group. These results indicate that instruction following was affected by the presence of the experimenter despite a history of no reinforcement for such behavior, and they suggest that instructional control may be strengthened by social contingencies.

Discriminative proprieties of Vary and Repeat contingencies

Pigeons were trained on an arbitrary matching-to-sample task in which Vary and Repeat contingencies served as sample stimuli. During the sample component, two keys were lit red and a four-peck sequence was reinforced if its frequency was less than a certain threshold (Vary sample) or if it comprised one of two target sequences (Repeat sample). During the comparison component, two keys were lit white and green, and correct choices depended on the previous sample contingency. Pigeons learned to emit high and low variability levels during the sample, and correct matching choices were obtained. In two discrimination testing phases, the requirement of variation (Vary sample) or of repetition (Repeat sample) was parametrically manipulated such that behavioral variability became undifferentiated between samples (low sample disparity) and then differentiated (high sample disparity) again. Accurate choices fell to chance under low sample disparity conditions, but improved under high disparity conditions. The results provide evidence that high and low variability levels can be produced in the absence of antecedent cues and that pigeons can accurately report whether they had experienced a Vary or a Repeat contingency, thus indicating that those contingencies may serve discriminative functions.

Varied but not necessarily random: Human performance under variability contingencies is affected by instructions

The goal of the present study was to evaluate the role of verbal stimuli in the production of response variability in humans. College students were distributed into three groups and asked to type three-digit sequences. Participants in the systematic group were instructed to produce sequences according to a rule of their choice; those in the random group were instructed to produce sequences according to chance; and those in the control group were not instructed about how to produce sequences. The experiment employed an ABA design. During the A phases, low-frequent sequences were reinforced (variability contingency), whereas during the B phase, reinforcement was withdrawn (extinction). The results indicated the following: (1) The instructions were efficient at producing systematic and random-like patterns for the systematic and random groups, respectively; in the absence of instructions, a mix of both patterns was observed. (2) Behavior was sensitive to extinction independently of the instructions provided. (3) Systematic patterns favored a more equiprobable distribution of sequences across trials. (4) Reaction times were longer for responding in a systematic than in a random-like fashion. The present findings suggest that individual differences in meeting variability contingencies may be due, at least partially, to instructional control.

Choice between contingencies of variation: effects of the requirement of variation upon preference.

The present study investigated whether choices between contingencies of variation are affected by the degree of variability required. For such, five pigeons were exposed to a concurrent chain schedule. In the initial links, responses in one key initiated the terminal link with the most stringent variation requirement while responses in the other key initiated the terminal link with the least stringent variation requirement. In both terminal links, four-responses sequences were reinforced according to a variation criterion, which favored less frequent and less recent sequences. The probability of reinforcement in the terminal link with the least stringent criterion was manipulated in order to generate similar percentage and rate of reinforcers in both terminal links. Choices for the terminal link with the least stringent criterion were more frequent than choices for the terminal link with the most stringent criterion. It is possible that situations that demand lower levels of behavior variability are chosen due to the lower response cost correlated to those situations.

Response–reinforcer dependency and resistance to change

The effects of the response-reinforcer dependency on resistance to change were studied in three experiments with rats. In Experiment 1, lever pressing produced reinforcers at similar rates after variable interreinforcer intervals in each component of a two-component multiple schedule. Across conditions, in the fixed component, all reinforcers were response-dependent; in the alternative component, the percentage of response-dependent reinforcers was 100, 50 (i.e., 50% response-dependent and 50% response-independent) or 10% (i.e., 10% response-dependent and 90% response-independent). Resistance to extinction was greater in the alternative than in the fixed component when the dependency in the former was 10%, but was similar between components when this dependency was 100 or 50%. In Experiment 2, a three-component multiple schedule was used. The dependency was 100% in one component and 10% in the other two. The 10% components differed on how reinforcers were programmed. In one component, as in Experiment 1, a reinforcer had to be collected before the scheduling of other response-dependent or independent reinforcers. In the other component, response-dependent and -independent reinforcers were programmed by superimposing a variable-time schedule on an independent variable-interval schedule. Regardless of the procedure used to program the dependency, resistance to extinction was greater in the 10% components than in the 100% component. These results were replicated in Experiment 3 in which, instead of extinction, VT schedules replaced the baseline schedules in each multiple-schedule component during the test. We argue that the relative change in dependency from Baseline to Test, which is greater when baseline dependencies are high rather than low, could account for the differential resistance to change in the present experiments. The inconsistencies in results across the present and previous experiments suggest that the effects of dependency on resistance to change are not well understood. Additional systematic analyses are important to further understand the effects of the response-reinforcer relation on resistance to change and to the development of a more comprehensive theory of behavioral persistence.

Effects of reinforcement value on instruction following under schedules of negative reinforcement

The effects of reinforcement value and social control on instruction following under a negative-reinforcement (escape) schedule were studied. Initially, responding produced timeouts from pressing a force cell under a low and a high force requirement on a fixed-ratio 1 schedule of reinforcement. Next, participants were reexposed to the low and high force requirements, but were instructed that the experimenter expected them to decrease the number of timeouts relative to the previous exposures to the procedure. Even though following the instruction led to a decrease in number of timeouts and to an increase in effort (i.e., was non-efficient), instruction following occurred consistently for each participant and was modulated by reinforcement value. That is, the decrease in the number of timeouts (i.e., instruction following) was lower under the high force requirement than under the low force requirement. These results replicate and extend previous findings that instructions interact with social and nonsocial contingencies in controlling human behavior.

Extinção e estímulos independentes da resposta: efeitos de relações de não-contingência sobre o comportamento

Extinction and presentation of response-independent stimuli are two traditional procedures to suspend a response-consequence contingency. The goal of this review is to discuss some similarities and divergences in the behavioral effects of those procedures. Among the similarities, we found responserate deceleration, stimulus control development, renewal, and increase in behavioral variability. Among the divergences, we observed the higher degree of responserate deceleration, the occurrence of emotional responses and behavioral contrast effects under extinction; superstitious behavior and reinstatement under response-independent stimuli conditions. Such behavioral effects were discussed in light of the similarities (non-contingency) and differences (presence versus absence of reinforcing stimuli) in programming those conditions.