Biases in social comparative judgments, such as those illustrated by above-average and comparative-optimism effects, are often regarded as products of motivated reasoning (e.g., self-enhancement). These effects, however, can also be produced by information-processing limitations or aspects of judgment processes that are not necessarily biased by motivational factors. In this article, the authors briefly review motivational accounts of biased comparative judgments, introduce a 3-stage model for understanding how people make comparative judgments, and then describe how various nonmotivational factors can influence the 3 stages of the comparative judgment process. Finally, the authors discuss several unresolved issues highlighted by their analysis, such as the interrelation between motivated and nonmotivated sources of bias and the influence of nonmotivated sources of bias on behavior.

The authors discuss the problem with failing to sample stimuli in social psychological experimentation. Although commonly construed as an issue for external validity, the authors emphasize how failure to sample stimuli also can threaten construct validity. They note some circumstances where the need for stimulus sampling is less obvious and more obvious, and they discuss some well-known cognitive biases that can contribute to the failure of researchers to see the need for stimulus sampling. Data are presented from undergraduate students (N = 106), graduate students (N = 72), and psychology faculty (N = 48) showing insensitivity to the need for stimulus sampling except when the problem is made rather obvious. Finally, some of the statistical implications of stimulus sampling with particular concern for power, effect size estimates, and data analysis strategies are noted.

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People are often presumed to be vulnerable to a desirability bias, namely, a tendency to be overoptimistic about a future outcome as a result of their preferences or desires for that outcome. In this article, this form of wishful thinking is distinguished from the more general concepts of motivated reasoning and overoptimism, and the evidence for this bias is reviewed. The authors argue that despite the prevalence of the idea that desires bias optimism, the empirical evidence regarding this possibility is limited. The potential for desires to depress rather than enhance optimism is discussed, and the authors advocate for greater research attention to mediators of both types of effects. Nine possible mediational accounts are described, and critical issues for future research on the desirability bias are discussed.

Three studies investigated the role of nonmotivated egocentric processes in comparative optimism (and pessimism). According to an egocentric-processes account, when people judge their comparative likelihood of experiencing an event (e.g., "Compared to the average person, how likely are you to become wealthy?"), they consider their own chances of experiencing the event more so than the referent's chances. This should produce higher comparative estimates when an event's absolute frequency is high rather than low-a prediction supported in Study 1, which manipulated event frequency through a novel, time frame manipulation. Study 2 empirically distinguished egocentrism from a related focalism account. In Study 3, comparative estimates were related to the perceived frequency of events, independent of the events' perceived desirability and controllability. Path analyses provided additional support for egocentrism, and systematic cases of comparative pessimism were observed as predicted by the egocentric-processes account.