The role of numerosity in judgments of overall frequency

Event frequency is conceptualized as being made up of information about the numerosity of the event within an episode and the episode frequency, which is the number of episodes in which the event occurs at least once. This conception was evaluated in 2 experiments that examined how numerosity information influences judgments of relative frequency. Exp I (32 17-32 yr old adults) demonstrates the basic phenomenon that judgments of frequency are strongly affected by the distribution of numerosities across multistimulus displays, such that Ss tend to judge as more frequent those events that occur often with high numerosities. Further, this effect was not substantially altered by instructing Ss that numerosity may not be predictive of overall frequency. Exp II (16 Ss) shows the effect to be general across different task orientations. Results suggest a model in which frequency judgments are assumed to depend on functionally distinct representations of numerosity and episode frequency information in memory. The model provides an account of the quantitative properties of the data and has implications for understanding the nature of the representation of frequency information. (19 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved).