Spillover bias in social and nonsocial judgments of diversity and variability.

In three experiments, we conceptually replicated and extended the spillover bias in judgments of diversity that was first reported by Daniels et al. (2017, Organizational Behavior and Human Decision Processes, 139, 92-105). In the first experiment, we showed that judgments of the ethnoracial diversity of groups of people were affected by the gender diversity of those people. In the second experiment, we extended this result to nonsocial stimuli by showing that judgments of the size diversity and size variability of groups of circles were affected by the color diversity of those circles. In the third experiment, we showed that judgments of the ethnoracial diversity of groups of people were affected by the color diversity of a group of circles in the background. These results suggest that diversity spillover bias is an extremely general phenomenon that occurs for both social and nonsocial judgments of diversity and variability. We propose that it occurs because people use the overall perceived diversity in a set of stimuli as a cue to judge diversity on any specific dimension.

Sample size bias in retrospective estimates of average duration.

People often estimate the average duration of several events (e.g., on average, how long does it take to drive from one's home to his or her office). While there is a great deal of research investigating estimates of duration for a single event, few studies have examined estimates when people must average across numerous stimuli or events. The current studies were designed to fill this gap by examining how people's estimates of average duration were influenced by the number of stimuli being averaged (i.e., the sample size). Based on research investigating the sample size bias, we predicted that participants' judgments of average duration would increase as the sample size increased. Across four studies, we demonstrated a sample size bias for estimates of average duration with different judgment types (numeric estimates and comparisons), study designs (between and within-subjects), and paradigms (observing images and performing tasks). The results are consistent with the more general notion that psychological representations of magnitudes in one dimension (e.g., quantity) can influence representations of magnitudes in another dimension (e.g., duration).

Sample size bias in judgments of perceptual averages.

Previous research has shown that people exhibit a sample size bias when judging the average of a set of stimuli on a single dimension. The more stimuli there are in the set, the greater people judge the average to be. This effect has been demonstrated reliably for judgments of the average likelihood that groups of people will experience negative, positive, and neutral events (Price, 2001; Price, Smith, & Lench, 2006) and also for estimates of the mean of sets of numbers (Smith & Price, 2010). The present research focuses on whether this effect is observed for judgments of average on a perceptual dimension. In 5 experiments we show that people's judgments of the average size of the squares in a set increase as the number of squares in the set increases. This effect occurs regardless of whether the squares in each set are presented simultaneously or sequentially; whether the squares in each set are different sizes or all the same size; and whether the response is a rating of size, an estimate of area, or a comparative judgment. These results are consistent with a priming account of the sample size bias, in which the sample size activates a representation of magnitude that directly biases the judgment of average.

Sample size bias in the estimation of means.

The present research concerns the hypothesis that intuitive estimates of the arithmetic mean of a sample of numbers tend to increase as a function of the sample size; that is, they reflect a systematic sample size bias. A similar bias has been observed when people judge the average member of a group of people on an inferred quantity (e.g., a disease risk; see Price, 2001; Price, Smith, & Lench, 2006). Until now, however, it has been unclear whether it would be observed when the stimuli were numbers, in which case the quantity need not be inferred, and "average" can be precisely defined as the arithmetic mean. In two experiments, participants estimated the arithmetic mean of 12 samples of numbers. In the first experiment, samples of from 5 to 20 numbers were presented simultaneously and participants quickly estimated their mean. In the second experiment, the numbers in each sample were presented sequentially. The results of both experiments confirmed the existence of a systematic sample size bias.

The effect of target group size on risk judgments and comparative optimism: the more, the riskier.

In 5 experiments, college students exhibited a group size effect on risk judgments. As the number of individuals in a target group increased, so did participants' judgments of the risk of the average member of the group for a variety of negative life events. This happened regardless of whether the stimuli consisted of photographs of real peers or stick-figure representations of peers. As a result, the degree to which participants exhibited comparative optimism (i.e., judged themselves to be at lower risk than their peers) also increased as the size of the comparison group increased. These results suggest that the typical comparative optimism effect reported so often in the literature might be, at least in part, a group size effect. Additional results include a group size effect on judgments of the likelihood that the average group member will experience positive and neutral events and a group size effect on perceptual judgments of the heights of stick figures. These latter results, in particular, support the existence of a simple, general cognitive mechanism that integrates stimulus numerosity into quantitative judgments about that stimulus.

General-knowledge overconfidence: a comparison of brazilian and american university students

People tend be overconfident in their general knowledge.That is, they tend to be more confident in their answers to general-knowlwdge questions than is warranted by the relative frequencey with which their anwers are actualy correc.Suprisingly,cross-national studies have consistenty shown that participants in many Asian conutries exhibit grater genera-knowledge overconfidence than participants in Great Britain and the United States. Because none of this cross-national rese