The group-diffusion effect is the tendency for people to judge themselves to be less likely to experience a negative outcome as the total number of people exposed to the threat increases — even when the probability of the outcome is explicitly presented (Yamaguchi, 1998). In Experiment 1 we replicated this effect for two health threat scenarios using a variant of Yamaguchi’s original experimental paradigm. In Experiment 2, we showed that people also judge themselves to be less likely to be selected in a lottery as the number of people playing the lottery increases. In Experiment 3, we showed that explicitly presenting the number of people expected to be selected eliminates the group-diffusion effect, and in Experiment 4 we showed that presenting the number expected to be affected by a health threat without presenting the total number exposed to the threat produces a reverse effect. We propose, therefore, that the group-diffusion effect is related to the ratio bias. Both effects occur when people make risk or likelihood judgments based on information presented as a ratio. The difference is that the group-diffusion effect occurs when the denominator of the relevant ratio is more salient than the numerator, while the ratio bias occurs when the numerator is more salient than the denominator.

Previous research demonstrates overestimation of rare events in judgment tasks, and underweighting of rare events in decisions from experience. The current paper presents three laboratory experiments and a field study that explore this pattern. The results suggest that the overestimation and underweighting pattern can emerge in parallel. Part of the difference between the two tendencies can be explained as a product of a contingent recency effect: Although the estimations reflect negative recency, choice behavior reflects positive recency. A similar pattern is observed in the field study: Immediately following an aversive rare-event (i.e., a suicide bombing) people believe the risk decreases (negative recency) but at the same time exhibit more cautious behavior (positive recency). The rest of the difference is consistent with two well established mechanisms: judgment error and the use of small samples in choice. Implications for the two-stage choice model are discussed.

Taxation policy is driven by many factors, including public opinion, but little research has examined the strength and stability of the public’s taxation preferences. This paper demonstrates one way in which preferences for progressiveness depend on the framing of the question asked. Participants indicated how they would share a fixed tax burden between two individuals who earned different amounts of money, either by adjusting the amount of tax paid by the two individuals, or by adjusting the amount of post-tax income retained. The units in which tax was described — amount of money or percentage tax rate — were manipulated orthogonally. There was a strong metric effect: Participants favored progressiveness more when tax was described as a percentage rather than amount. However, there was also a clear interaction: for amounts, participants favored progressiveness significantly more when considering post-tax money retained rather than tax paid; for percentages, no such effect was found.

We designed an experiment to test the robustness of Dana, Weber, and Kuang’s (DWK), 2007 results. DWK observed that, when participants were given a “costless” way — the click of a button — to ignore the consequences of their actions on others’ payoffs, they chose to remain ignorant and fair behavior diminished. By implementing a double-blind experiment together with a design that controls for alternative explanations for the observed behavior, we confirmed DWK’s findings.

Judgments of naturalness of foods tend to be more influenced by the process history of a food, rather than its actual constituents. Two types of processing of a “natural” food are to add something or to remove something. We report in this study, based on a large random sample of individuals from six countries (France, Germany, Italy, Switzerland, UK and USA) that additives are considered defining features of what makes a food not natural, whereas “subtractives” are almost never mentioned. In support of this, skim milk (with major subtraction of fat) is rated as more natural than whole milk with a small amount of natural vitamin D added. It is also noted that “additives” is a common word, with a synonym reported by a native speaker in 17 of 18 languages, whereas “subtractive” is lexicalized in only 1 of the 18 languages. We consider reasons for additivity dominance, relating it to omission bias, feature positive bias, and notions of purity.

Five studies demonstrated that people selectively use general moral principles to rationalize preferred moral conclusions. In Studies 1a and 1b, college students and community respondents were presented with variations on a traditional moral scenario that asked whether it was permissible to sacrifice one innocent man in order to save a greater number of people. Political liberals, but not relatively more conservative participants, were more likely to endorse consequentialism when the victim had a stereotypically White American name than when the victim had a stereotypically Black American name. Study 2 found evidence suggesting participants believe that the moral principles they are endorsing are general in nature: when presented sequentially with both versions of the scenario, liberals again showed a bias in their judgments to the initial scenario, but demonstrated consistency thereafter. Study 3 found conservatives were more likely to endorse the unintended killing of innocent civilians when Iraqis civilians were killed than when Americans civilians were killed, while liberals showed no significant effect. In Study 4, participants primed with patriotism were more likely to endorse consequentialism when Iraqi civilians were killed by American forces than were participants primed with multiculturalism. However, this was not the case when American civilians were killed by Iraqi forces. Implications for the role of reason in moral judgment are discussed.

When there are multiple competing objectives in a decision-making process, Multi-Attribute Choice scoring models are excellent tools, permitting the incorporation of both subjective and objective attributes. However, their accuracy depends upon the subjective techniques used to construct the attribute scales and their concomitant weights. Conventional techniques using local scales tend to overemphasize small differences in attribute measures, which may yield erroneous conclusions. The Range Sensitivity Principle (RSP) is often invoked to adjust attribute weights when local scales are used. In practice, however, decision makers often do not follow the prescriptions of the Range Sensitivity Principle and under-adjust the weights, resulting in potentially poor decisions. Examples are discussed as is a proposed solution: the use of global scales instead of local scales.

The deliberation-without-attention effect occurs when better decisions are made when people experience a period of distraction before a decision than when they make decisions immediately or when they spend time reflecting on the alternatives. This effect has been explained (e.g., Dijksterhuis, 2004) by the claim that people engage in unconscious deliberation when distracted and that unconscious thought is better suited for complex decisions than conscious thought. Experiments 1, 2A, and 2B in this study included a dominant alternative and failed to find evidence for this effect. Experiment 3 removed the dominant alternative and manipulated mode of thought within-subjects to eliminate alternative explanations for the failed replication. In all experiments participants did not make better decisions after unconscious thought; decisions were consistently better than chance when made immediately after the encoding of information. Encouraging people not to think about complex decisions appears to be unwarranted.