Teachers Know Best: The Impact of Taxonomic Distance and Teacher Competence on Evaluation of Negative Evidence

AbstractInductive generalization involves extending knowledge from sparse samples of evidence to arrive at broad conclusions. Most of the research in this area has focused on generalization from sparse samples of positive evidence (cases known to share properties with known cases; e.g., birds have hollow bones). Much less is known about generalization from samples of negative evidence (cases known to lack the properties attributed to known cases; e.g., bats do not have hollow bones). This paper reports the results from three experiments that examined factors that were believed to influence adults’ evaluation of negative evidence. Experiment 1 showed that when selecting among samples most useful for teaching about a particular category, participants (N=36) preferred samples with negative evidence rather than those with single, or additional, positive evidence. Experiment 2 revealed that participants (N=25) preferred samples with negative evidence that included a closer (rather than more distant) taxonomic match with the category in question. Finally, Experiment 3 revealed that adults (N=52) only preferred samples that provided a close match when evidence was provided by a competent informant. Overall these results emphasize the important role of pragmatic expectations when reasoning about samples that include negative evidence.

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