Gourdon, A. and Beck, S.R. (2010) Overcoming the framing effect when making decisions based on verbal probabilities: having more time is necessary but not enough’. In: 18th Annual Meeting of the European Society for Philosophy and Psychology (ESPP); 25-28 Aug 2010, Bochum-Essen, Germany. (Unpublished)

Abstract

Uncertain outcomes can be described by raw probabilities (e.g., There is 40% chance), but also by verbal probabilities (e.g., There is a chance, It is not absolutely certain). Beyond their probabilistic meaning verbal probabilities also have a directionality (Teigen & Brun, 1995), i.e. can be positive or negative. This directionality gives verbal probabilities a framing effect on decisions: when presented with two drugs for a headache, people typically prefer the one that is described by a positive verbal probability (e.g., some possibility) rather than the one introduced by a negative verbal probability (e.g., quite uncertain), even if both verbal probabilities are judged by other participants as having the same probabilistic meaning (Teigen & Brun, 1999). In this study we made the first investigation into the potential differences in processing directionality and probabilistic meaning that could explain the framing effect of the directionality. In experiment 1, twenty participants chose between two outcomes described by verbal probabilities. In one third of the trials the probabilistic meaning was controlled and the directionality varied. In another third the directionality was controlled and the probabilistic meaning varied. In the last third, both dimensions were different, reinforcing each other (congruent trials; e.g., a positive verbal probability carrying a high probabilistic meaning) or contradicting each other (incongruent trials; e.g. a negative verbal probability carrying a high probabilistic meaning). When both dimensions differed, participants chose more quickly between congruent verbal probabilities than between incongruent verbal probabilities. When only one dimension (directionality or probabilistic meaning) varied, participants chose more quickly between positive verbal probabilities and between ones of high probabilistic meaning than between negative verbal probabilities and between ones of low probabilistic meaning. Participants were also more accurate (i.e. chose the verbal probability carrying the highest probabilistic meaning most often) when choosing between congruent verbal probabilities and between positive verbal probabilities than when choosing between incongruent verbal probabilities and between negative verbal probabilities. Finally when the probabilistic meaning was held constant, participants tended to choose the outcome with the positive verbal probability more often than chance. In experiment 2, twenty participants did the same task under two time conditions: in the limited time condition, they had to answer within five seconds; in the unlimited time condition, they could take all the time they needed. The order of the time conditions was counterbalanced. Besides replicating the results of experiment 1, our aim was to investigate if the framing effect can be overcome under some conditions, here when relieving the time pressure. The same pattern as in experiment 1 was observed regarding accuracy and response time. However when the probabilistic meaning was held constant, actual answers indicated that the preference for the positive verbal probability was cancelled out when participants had all the time they needed. Even if relieving the time pressure, the framing effect occurred when the verbal probabilities to compare were incongruent. However if they had the same probabilistic meaning the framing effect was cancelled out. We discuss how these results can be integrated.

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