Conditioned suppression in operant variability and repetition

Author(s)

Paola Bisaccioni

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Psicologia (IP/SBD)
• Defense date: 2010-06-23

Examining board members

Maria Helena Leite Hunziker; Roberto Alves Banaco; Josele Regina de Oliveira Abreu Rodrigues

• Advisor: Maria Helena Leite Hunziker

Abstract

Conditioned suppression is defined as a decrease in the rate of a positively reinforced response during a stimulus which precedes an unavoidable shock. The reinforcement schedule used to maintain the baseline performance is an important variable in determining the degree of suppression. Therefore, the purpose of the present study was to compare the effects of different reinforcement schedules that selected behavioral variation or repetition in the conditioned suppression procedure. Rats were divided into two groups (n=6), named Variability (VAR) and Repetition (REP), that differed from each other in relation to the reinforcement schedules used to maintain the baseline. In VAR Group, rats were rewarded for variable response sequences. In REP Group, rats were rewarded for repeating a single LLLL sequence. After 25 sessions in these schedules, periods of light (20 sec.) were terminated with a brief, unavoidable shock (0.8 mA/ 0.5 sec.) for the two groups. The results indicated that the rate of operant response of all subjects decrease during the CS. Therefore all subjects showed strong suppression, the effect was more severe in REP Group. However, the difference obtained was small considering the differences in the reinforcement schedules that selected opposite performances related to behavioral variation. It was discussed that some parameters of this experiment could explain the small difference obtained here in contrast with previous studies. The results also showed that variation and repetition sequences are not affected by the aversive US. Thus, the data suggest that operant variability could be maintained in aversive contingencies (AU)