A constraint on comparisons: Equally detailed alternatives

Abstract Children's errors in collective comparison tasks are atributed to the comparison of the wrong classes. It is specifically hypothesized that alternative classes are erroneously formed subject to the constrain that the same kinds of properties are criterial for each alternative. This hypothesis, called the equally detailed alternatives hypothesis, is tested in three experiments with hierarchically organized stimuli and requests to compare a superordinate class and a nonincluded subclass, for example, dogs and yellow cats. In all three experiments 4-year-old children's comparisons were found to be in accord with the hypothesis. In the first experiment both perceptual and linguistic factors determine which classes are compared. In the second experiment, as predicted, erroneous subclass comparisons were more common when all subclasses were distinguished by the same kinds of properties. In the third experiment, the children were asked to partition the stimulus objects into the classes to be compared. The vast majority of partitions were erroneous and in accord with the hypothesis. Potential benefits of the constrain are considered.