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.     

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.     

Computerized Progressive Attentional Training (CPAT) Program: Effective Direct Intervention for Children with ADHD

We tested the efficacy of a pioneering intervention program grounded in a contemporary theoretical framework of attention and designed to directly improve the various attentional functions of children with ADHD. The computerized progressive attentional training (CPAT) program is composed of four sets of structured tasks that uniquely activate sustained attention, selective attention, orienting of attention, and executive attention. Performance was driven by tight schedules of feedback and participants automatically advanced in ordered levels of difficulty contingent upon performance. Twenty 6- to 13-year-old children with ADHD were assigned to the experimental group and received the CPAT sessions twice a week over an 8-week period. Sixteen age-matched control children with ADHD were assigned to the control group and participated in sessions of the same frequency, length, and format except that instead of performing the training tasks they played various computer games during the session. The experimental participants showed a significant improvement in nontrained measures of reading comprehension, and passage copying as well as a significant reduction of parents' reports of inattentiveness. No significant improvements were observed in the control group. We thus concluded that the above academic and attentional improvements were primarily due to the CPAT.     

Seek and ye shall find: test results are what you hypothesize they are

Expert clinicians were given batteries of psychodiagnostic test results (Rorschach, TAT, Draw-A-Person, Bender-Gestalt, Wechsler) to analyze. For half, a battery came along with a suggestion that the person suffers from Borderline Personality disorder, and for half, that battery was accompanied by a suggestion that he suffers from Paranoid Personality disorder. In Study 1, the suggestion was made indirectly, through a background story that preceded the test results. In Study 2, the suggestion was made directly, by the instructions given. The experts saw in the tests what they hypothesized to be there. In particular, the target diagnoses were rated higher when they were hypothesized than when they were not. Copyright © 1998 John Wiley & Sons, Ltd.     

White bear everywhere: Exploring the boundaries of the attentional white bear phenomenon

Some failures of selective attention may be explained by the attentional white bear (AWB) phenomenon Tsal & Makovski (Journal of Experimental Psychology: Human Perception and Performance 32:351?C363, 2006), which indicates that prior knowledge of a distractor location causes attention to be actively allocated to it. The AWB effect is demonstrated in a task that includes infrequent trials that involve two simultaneous dots embedded among flanker trials. The dot positioned at an expected distractor location is perceived as appearing before the dot at an expected empty location, indicating that attentional resources have initially been allocated to the expected distractor locations. The main goal of this study was to explore the boundaries of the AWB phenomenon by imposing perceptual, memory, and sensory constraints on the flanker task. The results showed that the AWB effect was obtained even when additional constraints severely taxed the information-processing system. We propose that a mandatory mechanism guides a fixed minimal amount of attention to expected distractor locations in a top-down manner.     

On the status of location in visual attention

The authors propose a distinction between four issues underlying the debate on the status of location in visual selective attention. Three of them concern the representation within which attention operates. The grouping question focuses on whether or not this representation segments the visual field into perceptual groups. The space-invariance question focuses on whether it describes objects in spatio-topic or in space-invariant coordinates. Finally, the feature-coding question concerns whether or not it contains information about objects' non-spatial features. The last issue focuses on whether or not attention can be guided preattentively towards items possessing certain pre-specified physical properties other than location, and is referred to as the attentional-guidance question. A critical survey of the literature within the proposed framework is presented. Based on its conclusions, the status of location in current research is outlined, and avenues for further research are suggested.