Effects of risk experience on choice behavior in rats under concurrent chained schedule

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Six male Wister rats, placed in the two-leveroperant boxes, were exposed under the concerrernt chained schedule. After competion of the initial link schedule (FR1), rats chose between two alternatives which were followed by two different consequences. Then they worked on the terminal link schedule (FR25) on the chosen alternative. If the sebjects chose the risk alternative, ten pellets or the black-out (BO) lasting ten seconds were presented with probility (p) 0.5. If the subjects selected the riskless alternative, five pellets with p=0.9 or BO (five seconds) with P=0.1 were occurred. Two rats experienced ten pellets (p=0.1) /BO (p=0.9) in the risk alternative and one pellet (p=0.9) /BO (p=0.1) in the riskless alternative. One session consisted of the forced choice trials in which subjects should select a pre-determined alternative and the free choice traials in which subjects could select one of two alternatives. In this non-separate condition, three of four rats whose pellet presentation probabilities (PPP) in risk vs.riskless alternative were 0.5 vs.0.9 showed risk aversion, but one rat showed risk prone. Two rats with PPP 0.1 vs.0.9 showed risk aversion. All rats showed very stable choices when FR ratios in the terminal link were increased and the forced choice trials changed to a Stubbs & Pliskoff type using two discriminative stimuli in the initial iink. In the separate condition, presentation of the consequence in the terminakl link was separated into five small consequences, e.g.a single presentation of ten-pellets separated into five multiple presentations of two-pellets. All five rats which showed risk averse in the non-separate condition produced unstable choice patterns the in separate condition.