Abstract
The present studies investigate one possible explanation as to why things are sometimes viewed as having become more variable in the present than they were in the past. It is proposed that such perceptions arise when variable information in the present is contrasted with a heterogeneity-reducing summary for the past. In order to test this hypothesis, subjects in two studies were asked to compare a collection of individual items with either the prior average alone or with the prior range and average. It was found that when comparisons were made to the prior average alone, people were much more likely to conclude that variability had increased.

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