Representativeness and fallacies of probability judgment

Representativeness is the name given to the heuristic people often employ when they judge the probability of a sample by how well it represents certain salient features of the population from which it was drawn. The representativeness heuristic has also been used to account for how people judge the probability that a given population is the source of some sample. The latter probability, however, depends on other factors (e.g., the population's prior probability) as well as on the sample characteristics. A review of existing evidence suggests that the ignoring of such factors, a central finding of the heuristics approach to judgment under uncertainty, is a phenomenon which is conceptually distinct from the representativeness heuristic. These factors (base rates, sample size, and predictability) do not always exert the proper influence on people's first-order probability judgments, but they are not ignored when people make second-order (i.e., confidence) judgments. Other fallacies and biases in subjective evaluations of probability are, however, direct causal results of the employment of representativeness. For example, representativeness may be applied to the wrong features. Most devastating, perhaps, is that subjective probability judgments obey a logic of representativeness judgments, even though probability ought to obey an altogether different logic. Yet although the role of representativeness judgments in probability estimation leaves a lot to be desired, it is hard to envision prediction and inference completely unaided by representativeness.     

The effects of narrative context on French verbal inflections: A developmental perspective

This experiment examines how narrative context affects French subjects' selection of past imperfective (imparfait) vs. perfective inflections with different predicate types. Adults and 10-year-old children were asked to inflect verbs presented in their written infinitive form in two conditions: (a) in isolated sentences; (b) embedded in the beginning, middle, or end of narratives. Regardless of conditions, the adults rarely used theimparfait with punctual resultative predicates. In both conditions, the frequency ofimparfait was high with durative predicates, particularly with aresultative ones, but it varied with position in the narratives, being highest at the beginning and lowest at the end. Although the children also used the imparfait frequently with durative predicates, they overgeneralized it to punctual resultative ones, regardless of conditions and of positions. These results show that adult uses of the imperfective/perfective distinction are determined by both predicate properties and grounding in narrative context. The children are less sensitive to some predicate properties than the adults and they do not differentiate imperfective/perfective aspect consistently as a function of discourse context.     

Commentary on Wolford,Taylor, and Beck: The conjunction fallacy?

AlthoughP(A&B|X) can never exceedP(A|X) (the conjunction rule), it is possible forP(X|A&B) to exceedP(X|A). Hence, people who rankA&B as more probable thanA are not necessarily violating any normative rule if the ranking is done in terms of the probability of these events to yield an eventX. Wolford, Taylor, and Beck (1990) have argued that this indeed is what happens in some problems (e.g. Tversky& Kahneman’s [1983] Linda problem). The claim made here is that the Linda problem is hard to reconcile with this interpretation; that there is little if any evidence that subjects utilize this interpretation; and that in any case, representativeness can account for all Linda problem results.     

Ideal evidence, relevance and second-order probabilities

Conclusion The concepts of supportive evidence and of relevant evidence seem very closely related to each other. Supportive evidence is clearly always relevant as well. But must relevant evidence be defined as evidence which is either supportive or weakeking? In an explicit or implicit manner, this is indeed the position of many philosophers. The paradox of ideal evidence, however, shows us that this is to restrictive. Besides increasing or decreasing the probability attached to some hypothesis, evidence can alter or interact with the background assumptions underlying the hypothesis.In most circumstances, the (post hoc) relevance of evidence can indeed be judged by its effect on the confidence one attaches to hypotheses. Occasionally, as in the circumstances described by Example I, and more generally called the Paradox of Ideal Evidence, the relevance of evidence to an hypothesis can only be understood by appeal to a broader sense.In Memory of My Father. Yehoshua Bar-HillelThe author wishes to thank Haim Gaifman for a most thoughtful and constructive review of an earlier draft of this paper.     

Neuroticism as mental noise: a relation between neuroticism and reaction time standard deviations

Those higher in neuroticism are often more variable in their behavior and experience. On the basis of this observation, the authors hypothesized that the trait of neuroticism might be correlated with the variability of performance pertaining to relatively basic cognitive operations. Three studies involving 242 college undergraduates supported this prediction in that neuroticism correlated positively with the variability of performance across trials of reaction time tasks. These results link neuroticism to cognitive noise that intervenes between stimulus and response. Such noise has been associated with executive dysfunctions (e.g., frontal lobe injury) in previous research. The present findings are potentially useful for understanding why neuroticism often correlates with variations in the functionality of cognition and behavior.     

Don't worry, be happy? Neuroticism, trait-consistent affect regulation, and performance

People regulate their affect either to feel good or to achieve instrumental success. The present experiments show that when driven by performance goals, people can be motivated to experience unpleasant affect when it is trait-consistent, because of its instrumental benefits (e.g., M. Tamir & M. D. Robinson, 2004). In 4 studies, individuals high in neuroticism were more likely than those low in neuroticism to choose to increase their level of worry, as indicated by self-reported preferences (Study 1) and by behavioral choices in experimental settings (Studies 2-4). As predicted, such preferences were evident when expecting to perform demanding tasks but not when expecting an undemanding task (Study 2). Study 4 suggests that such preferences for short-term unpleasant affect may be beneficial to performance.     

Changing views about personality disorders: Comment about the prospective studies CIC, CLPS, and MSAD

Three large-scale prospective studies (Children in the Community Study [CIC; Cohen, Crawford, Johnson, & Kasen, this issue], Collaborative Longitudinal Personality Disorders Study [CLPS; Skodol et al., this issue], and the McLean Study of Adult Development [MSAD; Zanarini, Frankenburg, Hennen, Reich, & Silk, this issue]) are discussed with respect to the following issues: shared and complementary features of the study designs, evidence for stable and changing personality disorder features, methodological issues (reliability, stability, and invariance), the relationship between Axis I and II disorders, and dimensional versus categorical representations of personality disorders.     

A facilitative role for corticosterone in the acquisition of a spatial task under moderate stress

Emotionally charged experiences alter memory storage via the activation of hormonal systems. Previously, we have shown that compared with rats trained for a massed spatial learning task in the water maze in warm water (25°C), animals that were trained in cold water (19°C) performed better and showed higher levels of the stress hormone corticosterone. Here, we examined whether manipulating the levels of corticosterone can determine the strength of spatial information acquisition and retention. Rats were injected with metyrapone (25, 50, and 75 mg/kg, i.p.) or with corticosterone (10 and 25 mg/kg, i.p.) and trained in a massed spatial task in either cold (19°C) or warm (25°C) water. We found that whereas animals injected with vehicle performed well in the spatial task in cold water (moderate stress), rats injected with the intermediate metyrapone dose showed impairment in performance. Moreover, whereas animals injected with vehicle on average did not perform well in warm water (mild stress), rats injected with the lower corticosterone dose showed improvement in performance in warm water. These two mirror experiments of corticosterone blockade and enhancement strongly suggest that corticosterone is instrumental in the acquisition and retention of the spatial learning task.     

TRAINING STAFF TO INCREASE MANDING IN STUDENTS WITH AUTISM: TWO PRELIMINARY CASE STUDIES

Two case studies evaluated two versions of behavioral skills training on peer‐to‐peer manding. Case Study 1 evaluated the full package of instructions, modeling, rehearsal, and feedback, and Case Study 2 used modeling and feedback only. Both case studies employed AB designs. In both case studies, staff increased correct teaching responses, and students increased the number of independent peer‐to peer mands. These pilot data suggest that staff can readily acquire teaching skills to increase peer‐to‐peer manding and that modeling and feedback may be sufficient to train staff to do so. Copyright © 2012 John Wiley & Sons, Ltd.