The present experiment studied the relationship between interresponse intervals and behavioral variability. Subjects emitted sequences of 4 keypresses on two keys on a variability schedule that delivered points when the current 4-response sequence differed from the previous 5 sequences. Three experimental conditions were studied; no interresponse interval, 4-s interresponse interval and 8-s interresponse interval. Interresponse intervals followed each of the first three responses in each sequence. Two groups were used to study initial training histories. Group 1 was first exposed to the no-interresponse interval condition. Group 2 was first exposed to the 4-s interresponse interval condition. Subjects were then exposed to the different interresponse interval conditions. There was little change in variability across conditions. However, the variability observed in the subjects first exposed to the 4-s interresponse interval was greater than the variability observed in subjects first exposed to no-interresponse interval. There was higher-order response patterning in both groups, but it was more pronounced in the no-interresponse interval group.

Post-reinforcement pauses (PRP) and interresponse times (IRTs) were examined to determine if these two temporal units changed in a similar fashion as a function of the delivery of differential reinforcement. Two experiments were conducted. In Experiment 1, four pigeons were exposed to a series of procedures in which PRP and IRT durations were gradually increased and then decreased. A fixed-ratio two (FR 2) differentiation schedule was used. Reinforcement was delivered if the PRP or IRT durations were greater than (PRP > and IRT > procedures) or less than (PRP < and IRT < procedures) specified temporal criteria. Criteria were gradually changed across procedures. Results showed that PRPs and IRTs changed in accordance with the differential reinforcement as specified by the various contingencies. When PRPs and IRTs were free to vary, the PRPs tended to change in a direction consistent with the IRT shaping contingencys whereas, the IRTs tended to shorten regardless of the PRP shaping contingency. In Experiment 2, two subjects were exposed to both an FR 2 and FR 1 schedule to determine if schedule size influenced the effects obtained on the differentiation procedures. PRPs were systematically changed using a differentiation procedure with a response requirement of either FR 1 or FR 2. Results showed similar changes in PRP durations between FR 1 and FR 2 differentiation procedures. An analysis of errors made on each shaping condition in both experiments was conducted to determine whether PRPs or IRTs were more susceptible to the differential reinforcement contingencies. Fewer errors were made on the PRP shaping conditions, indicating that PRPs were more easily changed. Implications for a comprehensive theory of reinforcement were discussed.

Made available in DSpace on 2016-04-29T13:17:45Z (GMT). No. of bitstreams: 1 Fernanda Rizzi Bitondi.pdf: 1390449 bytes, checksum: c3d88238b2946cc2655e04fd9337cc96 (MD5) Previous issue date: 2012-05-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The aim of this study was to evaluate the effectiveness of two procedures, Discrete Trial (DT) and Discrete Trial with Interresponse Interval (DT/IRI), on the production of behavioral variability in different conditions (directly reinforced and induced) and determine what condition, in each procedure, would facilitate the selection of an initial sequence of low probability. Were selected 18 college students with baseline performance measured by U-valeu, that was equal or less than 0,5. They were divided into the two procedures and subdivided into three groups with three participants (VAR, YOKE and CON). The task was to form images on the computer screen by pressing two keys (left and right) on lateral keyboards. The unit was four responses to the keys. In both procedures, a piece of the image, a tone and 0,5 seconds was used to reinforce sequences that attended the contingency s criterion, and a timeout of 1,0 second, if not. Only the DT/IRI had a 0,5 second interval after the first three responses of the sequence. The experiment had three phases. In Phase I, baseline, sequences was continuous reinforced (CRF). For two groups (DT- VAR and DT/IRI-VAR) in Phase 2, variability was direct reinforced on 15 sequences, mean that the less frequent and less recent sequence had more probability of been reinforced than the others, and a target sequence (less frequent sequence at baseline) was reinforced in CRF. In Phase 3, the distribution of reinforcement of the prior phase was yoked for the 15 sequences and another target sequence was reinforced in CRF. For the groups DT-YOKE and DT/IRI-YOKE, the phase s exposure was reversed, whereas in Phase 2 the distribution of reinforcement was yoked to the performance of the VAR groups. In groups DT-CON and DT/IRI-CON, only the target sequence was reinforced in both phases. The results showed that variability increased in the first session of Phase 2 for all participants. The DT-YOKE group showed the highest levels of variability within this procedure. In the DT/IRI procedure, this was true for the group DT/IRI-VAR. With regard to the selection of the target sequence the groups that had higher percentages of selection in all sessions were DT-CON and DT/IRI-VAR, respectively within each procedure. It was noted that both procedures produced the selection of the target sequence, but is seems that the use of IRI produced a more variable performance, when it was directly reinforced, allowing the selection of the target sequence to occur more rapidly / O objetivo do estudo foi avaliar a efetividade de dois procedimentos, Tentativa Discreta (TD) e Tentativa Discreta com Intervalo entre as Respostas (TD/IRI), na produção da variabilidade comportamental em diferentes condições (diretamente reforçada e induzida) e averiguar que condição, em cada procedimento, mais facilitaria a seleção de uma sequência de baixa probabilidade inicial. Selecionou-se 18 universitários com um desempenho na linha de base, medido pelo índice U, igual ou inferior a 0,5. Estes foram divididos nos dois procedimentos e subdivididos em três grupos com três participantes (VAR, ACO e CON). A tarefa consistia em formar figuras na tela do computador pressionando duas teclas (direita e esquerda) de teclados laterais. A unidade comportamental era quatro respostas às teclas. Nos dois procedimentos apresentava-se um pedaço da figura, um tom e 0,5 segundo, caso a sequência fosse passível de reforço, e um timeout de 1,0 segundo, caso não fosse. Somente no TD/IRI havia um IRI de 0,5 segundo após as três primeiras respostas da sequência. O experimento continha três fases. Na Fase 1, linha de base, vigorava o reforçamento contínuo (CRF) das 16 sequências. Para dois grupos (TD-VAR e TD/IRI-VAR) na Fase 2 havia o reforçamento direto da variabilidade, para 15 sequências, no qual a sequência menos frequente e menos recente teria maior probabilidade de ser reforçada, e CRF de uma sequência alvo (sequência menos frequente na linha de base). Na Fase 3, havia a distribuição acoplada dos reforços da fase anterior para as 15 sequências e CRF de outra sequência alvo. Para os grupos TD-ACO e TD/IRI-ACO a ordem de exposição às fases foi inversa, visto que na Fase 2 a distribuição de reforços foi acoplada ao desempenho dos participantes dos grupos VAR. Nos grupos TD-CON e TD/IRI-CON havia somente o CRF da sequência alvo nas duas fases. Os resultados mostraram que a variabilidade aumentou na primeira sessão da Fase 2 para todos os participantes. O grupo TD-ACO foi o que apresentou maior índices de variabilidade dentro deste procedimento. Já no TD/IRI, isto foi verdadeiro para o grupo TD/IRI-VAR. Com relação à seleção da sequência alvo, os grupos que apresentaram maiores porcentagens de seleção em todas as sessões foram TD-CON e TD/IRI-VAR, respectivamente dentro de cada procedimento. Notou-se que os dois procedimentos produziram seleção da sequência alvo, mas parece que o uso do IRI produziu um responder mais variável, quando este foi diretamente reforçado, o que possibilitou que a seleção da sequência alvo ocorresse mais rapidamente