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RESix experiments studied relative frequency judgment and recall of sequentially presented items drawn from 2 distinct categories (i.e., city and animal). The experiments show that judged frequencies of categories of sequentially encountered stimuli are affected by certain properties of the sequence configuration. We found (a) a "first-run effect" whereby people overestimated the frequency of a given category when that category was the first "repeated" category to occur in the sequence and (b) a dissociation between judgments and recall; respondents may judge 1 event more likely than the other and yet recall more instances of the latter. Specifically, the distribution of recalled items does not correspond to the frequency estimates for the event categories, indicating that participants do not make frequency judgments by sampling their memory for individual items as implied by other accounts such as the availability heuristic (Tversky & Kahneman, 1973) and the availability process model (Hastie & Park, 1986). We interpret these findings as reflecting the operation of a judgment heuristic sensitive to sequential patterns and offer an account for the relationship between memory and judged frequencies of sequentially encountered stimuli. (Contains 4 footnotes, 3 tables, and 2 figures.)

In 5 experiments, we studied precautionary decisions in which participants decided whether or not to buy insurance with specified cost against an undesirable event with specified probability and cost. We compared the risks taken for precautionary decisions with those taken for equivalent monetary gambles. Fitting these data to Tversky and Kahneman's (1992) prospect theory, we found that the weighting function required to model precautionary decisions differed from that required for monetary gambles. This result indicates a failure of the descriptive invariance axiom of expected utility theory. For precautionary decisions, people overweighted small, medium-sized, and moderately large probabilities--they exaggerated risks. This effect is not anticipated by prospect theory or experience-based decision research (Hertwig, Barron, Weber, & Erev, 2004). We found evidence that exaggerated risk is caused by the accessibility of events in memory: The weighting function varies as a function of the accessibility of events. This suggests that people's experiences of events leak into decisions even when risk information is explicitly provided. Our findings highlight a need to investigate how variation in decision content produces variation in preferences for risk. (Contains 9 tables, 6 figures and 1 footnote.)

Any individual's response intended to be random should be as probable as any other. However, 3 experiments show that many people's independent responses depart from the expected chance distribution. Participants responding to instructions of chance and related concepts favor the available options unequally in a similar way. Consequently, in hide-and-seek games, hiders converge on certain locations and are thereby detected beyond chance by seekers who share their preferences. People agree on salient and on nonsalient options, both of which are preferred under different instructions and even in the absence of instructions. Group responses strongly correlate under diverse, even opposing (e.g., competitive and cooperative) directions. Apparently, common default tendencies, combining random and aesthetic choices, are only somewhat modified under specific instructions. Maximal agreement with others is obtained through one's own aesthetic choices. Hence, implementing one's personal aesthetic preferences succeeds in matching others' choices even better than deliberate mutual coordination efforts. These results broadly replicate in 1- and 2-dimensional tasks. Implications of the findings, their possible roots, and their connection to constructs from, e.g., game theory and subjective-complexity research, are discussed. (Contains 1 footnote, 14 tables, and 7 figures.)

A proposed remedy for biased affective forecasts is to base judgments on the actual feelings of people (surrogates) currently experiencing the event, rather than using imagination which conjures an inaccurate vision of the future. Gilbert et al. (2009) forced people to use surrogate reports by withholding all event information, resulting in better predictions. However, in life surrogate information rarely supplants event information--can people effectively integrate both types of information into their judgments? In five studies, respondents predicted the impact of a health state on their own happiness. Respondents incorporated surrogate information into their judgments both in the presence and absence of event information. However, they inappropriately discounted other people's experiences as a valid predictor of their own--particularly in the presence of event information--and imagined their happiness would be different to surrogates' happiness. Excluding preexisting event knowledge, changing the size of the surrogate sample, or increasing the size of the response scale did not alter the adjustment. Although surrogate information improved affective forecasts, its influence was diminished by the presence of event information. (Contains 2 figures, 4 tables and 2 footnotes.)

In 5 experiments, we studied precautionary decisions in which participants decided whether or not to buy insurance with specified cost against an undesirable event with specified probability and cost. We compared the risks taken for precautionary decisions with those taken for equivalent monetary gambles. Fitting these data to Tversky and Kahneman's (1992) prospect theory, we found that the weighting function required to model precautionary decisions differed from that required for monetary gambles. This result indicates a failure of the descriptive invariance axiom of expected utility theory. For precautionary decisions, people overweighted small, medium-sized, and moderately large probabilities--they exaggerated risks. This effect is not anticipated by prospect theory or experience-based decision research (Hertwig, Barron, Weber, & Erev, 2004). We found evidence that exaggerated risk is caused by the accessibility of events in memory: The weighting function varies as a function of the accessibility of events. This suggests that people's experiences of events leak into decisions even when risk information is explicitly provided. Our findings highlight a need to investigate how variation in decision content produces variation in preferences for risk. Keywords: probability, accessibility, risk exaggeration, frequency, precautionary decisions DOI: 10.1037/a0017039

Any individual's response intended to be random should be as probable as any other. However, 3 experiments show that many people's independent responses depart from the expected chance distribution. Participants responding to instructions of chance and related concepts favor the available options unequally in a similar way. Consequently, in hide-and-seek games, hiders converge on certain locations and are thereby detected beyond chance by seekers who share their preferences. People agree on salient and on nonsalient options, both of which are preferred under different instructions and even in the absence of instructions. Group responses strongly correlate under diverse, even opposing (e.g., competitive and cooperative) directions. Apparently, common default tendencies, combining random and aesthetic choices, are only somewhat modified under specific instructions. Maximal agreement with others is obtained through one's own aesthetic choices. Hence, implementing one's personal aesthetic preferences succeeds in matching others' choices even better than deliberate mutual coordination efforts. These results broadly replicate in 1- and 2-dimensional tasks. Implications of the findings, their possible roots, and their connection to constructs from, e.g., game theory and subjective-complexity research, are discussed. Keywords: randomness, hide-and-seek, competition versus cooperation, aesthetics, default tendencies Supplemental materials: http://dx.doi.org/10.1037/0096-1523.35.1.203.supp