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. 2014;61(5):356-67.
doi: 10.1027/1618-3169/a000255.

Two heads are better than one, but how much? Evidence that people's use of causal integration rules does not always conform to normative standards

Miguel A Vadillo  1 , Nerea Ortega-Castro  2 , Itxaso Barberia  2 , A G Baker  3
Affiliations

Two heads are better than one, but how much? Evidence that people's use of causal integration rules does not always conform to normative standards

Miguel A Vadillo et al. Exp Psychol. 2014.

Abstract

Many theories of causal learning and causal induction differ in their assumptions about how people combine the causal impact of several causes presented in compound. Some theories propose that when several causes are present, their joint causal impact is equal to the linear sum of the individual impact of each cause. However, some recent theories propose that the causal impact of several causes needs to be combined by means of a noisy-OR integration rule. In other words, the probability of the effect given several causes would be equal to the sum of the probability of the effect given each cause in isolation minus the overlap between those probabilities. In the present series of experiments, participants were given information about the causal impact of several causes and then they were asked what compounds of those causes they would prefer to use if they wanted to produce the effect. The results of these experiments suggest that participants actually use a variety of strategies, including not only the linear and the noisy-OR integration rules, but also averaging the impact of several causes.

Keywords: causal reasoning; integration rules; summation.

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Figures

Figure 1
Figure 1. Pattern of preferences predicted by the noisy-OR rule and actual proportion of participants preferring the compound AB over CE and over DE in Experiments 1A–4A and Experiment 5A. The 0.50 axis represents indifference between AB and the other options. Proportions above 0.50 represent a preference for AB over the other options. Asterisks are placed upon values that are significantly different from .50 in a binomial test with α = .05.
Figure 2
Figure 2. Proportion of participants preferring the compound AB over CE and over DE in Experiments 4B and 5B. To make the comparison with Experiment 4B easier, preferences were reverse-scored in Experiment 5B (see the main text for further details). Asterisks are placed upon values that are significantly different from .50 with α = .05.
Figure 3
Figure 3. Frequencies of responses to the probability ratings requested to the participants in Experiments 4A, 4B, and 5B. The x-axis represents specific values of judgments given by participants and the y-axis the frequency of those values in our sample.
Figure 4
Figure 4. Frequencies of responses to the probability ratings requested to the participants in Experiment 5A.
See this image and copyright information in PMC

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