Comportamento de escolha humana: influência da manipulação das probabilidades de reforçamento, instruções e exposição às contingências

Abstract

A chained probabilistic choice procedure was used to observe if human participants were sensible to the manipulation of the probabilities of reinforcement. In this procedure there was an initial screen showing two stimuli a circle and a triangle (initial chain). Choices in the circle led to a second screen (final chain) with a stimulus, and triangle choices opened a second screen with 4 stimuli. After choosing the final chain the participant could score or not depending on the value of the probabilistic pair programmed to the circle or triangle choices. Three pairs of probabilistic choice were used (0. 10-0. 10, 0.50-0.50 e 0.90-0.90) and the change between them allowed 6 different sequences. Each one of the 30 participants went through a sequence that, beyond the reinforcement probabilities, also had initial and final (extinction) base line sessions. A criterion of 10% of establishment of preference between the last sessions was used for the change of probability. In the condition that the probabilistic pair was 0.10-0.10 all the participants got an instruction to choose the circle. Was observed that the participants did not discriminate the different probabilities of reinforcement and that even though with a low probability (0.10) the instruction did not controlled the preference of the participants. Experiment 2 aimed to verify if the number of trials to reinforcement of the final chain controlled the preference, and another 5 participants were exposed to 4 different probabilistic pairs. Each participant was exposed to the pair for 3 sessions with 40 trials each. Thus, each participant went through exactly 12 experimental sessions always in the same row: 0.010-0.00, 0.00-0.10, 0.90-0.00 and 0.00-0.90; the former probabilistic pair is always the triangle and the latter the circle. The data of the second experiment shows the established control by the reinforcement and not by the number of trials.