Distortion of probability and outcome information in risky decisions

Substantial evidence indicates that information is distorted during decision making, but very few studies have assessed the distortion of probability and outcome information in risky decisions. In two studies involving six binary decisions (e.g., banning blood donations from people who have visited England, because of “mad cow disease”), student and nonstudent participants distorted their evaluations of probability and outcome information in the direction of their preferred decision alternative and used these biased evaluations to update their preferences. Participants also evaluated the utilities of possible outcomes more positively when the outcomes could follow only from the preferred alternative and more negatively when they could follow only from the competing alternative. Such circular reasoning is antithetical to the normative consequentialist principles underlying decision analysis. Presenting numerical information as precise values or as ranges of values did not significantly affect information distortion, apparently because the manipulation did not affect perceived ambiguity as intended.     

Precision of probability information and prominence of outcomes: A description and evaluation of decisions under uncertainty

Information about event probability upon which decisions depend may be more or less precise. The first section of this paper reports three experiments that investigated the relationship between this type of imprecision and the prominence that outcomes obtain in decisions. Participants had to rank order sets of six lotteries according to attractiveness. While the lotteries’ values were always precisely known precision of information about lottery chances varied. These experiments showed that increasing ambiguity tied decisions closer to lottery values. The second section shows that modeling participants’ decisions with the contingent weighting model suggests that this outcome prominence effect was not necessarily caused by any change in the respective weighting of probability and outcome information, but that it had probably occurred for purely mathematical reasons. The third part of this paper explores, by means of a computer simulation, (i) which weighting strategy is optimal when probabilities are imprecise and (ii) how participants’ decision behavior compared to a simple, but better adapted strategy. It shows that the weighting of probability information should not change with decreasing precision and it implies that participants’ performance suffered most from a lack of strategic consequence. Implications for decision making policy in general are discussed.     

Mere repeated exposure and experimental stress as determiners of stimulus evaluations

From Berlyne's theorizing concerning the determinants of hedonic value of a stimulus it was hypothesized that importance of evaluative judgments and frequency of exposure would interact in determining the favorability of affective ratings. This prediction was confirmed by the data. Increasing the importance of the rating task decreased the favorability of the ratings of low-frequency stimuli but enhanced the ratings of high-frequency stimuli.The experiments reported here were conducted at the Laboratorium voor Experimentele Sociale Psychologie at Leuven. This article is based on the author's doctoral dissertation, which was supervised by J. M. Nuttin, Jr. I would also like to thank J. M. Nuttin, Jr., E. Van Avermaet, and J. Hatcher for their helpful comments on a previous draft.     

Confirmation bias in sequential information search after preliminary decisions: an expansion of dissonance theoretical research on selective exposure to information

Research on selective exposure to information consistently shows that, after having made a decision, people prefer supporting over conflicting information. However, in all of these experiments participants were given an overview of all available pieces of information, selected them simultaneously, and did not process the requested information during the selection phase. In the present research the authors show that an even stronger preference for supporting information arises if information is presented and processed sequentially instead of simultaneously (Experiment 1), and they demonstrate that this stronger confirmation bias is due to sequential presentation and not to sequential processing of information (Experiment 2). The authors provide evidence that the increase in confirmation bias under sequential presentation is caused by heightened commitment due to the participants' increased focusing on their decision (Experiments 3 and 4).     

Word frequency and age of acquisition as determiners of picture-naming latency

In multiple-regression analysis of picture-naming latencies from an experiment modelled on Oldfield and Wingfield's (1965), with 94 stimuli and 37 adult subjects, two word frequency measures had insignificant beta weights, while two measures estimating age at which the word was learned had highly significant weights. Objects whose names were learned early were named faster. This result may have important implications for the interpretation of studies using word frequency as a critical variable. It is suggested that word retrieval may be a one-stage process that depends upon the age at which a word was learned.     

Imagery, concreteness, and meaningfulness as determiners of the emotionality of words when meaning is controlled.

We studied variables that influenced rated emotionality value of words and the contribution of each one. 218 subjects rated each word in a list of 98 pairs of words (196 words), one concrete word and one abstract word in each pair, on imagery, concreteness, meaningfulness, and emotionality. Date of entry of each word into Spanish and word length were also examined. Stepwise multiple regression procedures were performed to evaluate the contribution made by each variable to over-all emotionality values. 39.06% of the emotionality variance was explained by imagery. Concreteness and meaningfulness values contributed 3.62% and 2.82%, respectively. Word length and date of entry were rejected in the final equation, as their contributions were minimal.     

Apparent distance vs. apparent size as determiners of figural after-effects

Abstract.— Sutherland's (1954) much discussed experimental design was analysed in a new fashion. When the original experiment was repeated as such, the expected FAE was found. However, when the same IFs and TFs were presented in a vertical position, no significant FAEs were found. The results lend support to the interpretation presented earlier by Kolehmainen (1968): The FAE found by Sutherland was apparently due to an uncontrolled binocular disparity resulting in a different localization of stimulus figures in respect to the fixation point.