Perception of randomness and predicting uncertain events

Using randomly generated sequences of binary events we asked participants to make predictions about the next event. It turned out that while predicting uncertain events, people do not behave unsystematically. Our research identifies four types of relatively consistent strategies for predicting uncertain binary events: a strategy immune to short-run sequential dependencies consisting of the persistent prediction of long-run majority events, hereafter called the long-run momentum strategy; a strategy immune to short-run sequential dependencies consisting of the persistent prediction of long-run minority events, called the long-run contrarian strategy; a strategy sensitive to short-run sequential dependencies consisting of the prediction of short-run majority events, called the short-run momentum strategy; and a strategy sensitive to short-run sequential dependencies consisting of the prediction of short-run minority events, called the short-run contrarian strategy. When the character of events remains unknown, the most common strategy is the short-run momentum strategy. With the increase of a perceived randomness of the situation, people tend more often to use the short-run contrarian strategy. People differ in their general beliefs about the continuation or reversal of a trend in various natural and social processes. Trend believers, when facing sequences of binary events commonly perceived as random, tend to use momentum strategies, whereas those who believe in the trend's reversal tend to use contrarian strategies.     

Explaining the gambler's fallacy: Testing a gestalt explanation versus the “law of small numbers”

The present study tests a gestalt (closure) explanation for the gambler's fallacy which posits that runs in random events will be expected to reverse only when the run is open or ongoing. This is contrasted with the law of small numbers explanation suggesting that people expect random outcomes to balance out generally. Sixty-one university students placed hypothetical guesses and bets on a series of coin tosses. Either heads or tails were dominant (8 versus 4). In a closed run condition the run ended prior to the critical trial (e.g., HHHT), and in an open run condition the run remained open (e.g., THHH). As hypothesised, participants showed the gambler's fallacy in the open run condition, but not in the closed run condition. This difference is not due to differential memory for the outcomes. Men, and people with more previous experience gambling, were also found to be more prone to the gambler's fallacy. It is argued that the gestalt explanation best explains the results.     

Sympathetic magic and perceptions of randomness: The hot hand versus the gambler's fallacy

The gambler's fallacy and hot hand were studied in predictions about outcomes of coin tosses. A critical trial occurred when participants made predictions after a “run” of four heads or tails. Participants' attention was manipulated to focus on the person flipping the coin, the coin, or neither (control group) as a possible cause of the run. We also manipulated whether or not there was a change in who tossed the coin. In the control condition the standard reversal was observed (gambler's fallacy); however, when participants focused on the person, and it was that same person who conducted the run and critical coin toss, more people chose in the direction of continuation (hot hand). Directing attention to the person tossing the run seemed to prompt participants to behave as if that individual was “hot” in terms of getting a specific outcome (e.g., heads), as if by sympathetic magic, thus eliminating the gambler's fallacy.     

Base-rate neglect as a function of base rates in probabilistic contingency learning

When humans predict criterion events based on probabilistic predictors, they often lend excessive weight to the predictor and insufficient weight to the base rate of the criterion event. In an operant analysis, using a matching-to-sample paradigm, Goodie and Fantino (1996) showed that humans exhibit base-rate neglect when predictors are associated with criterion events through physical similarity. In partial replications of their studies, we demonstrated similar effects when the predictors resembled the criterion events in terms of similarly skewed base rates. Participants' predictions were biased toward the more (or less) frequent criterion event following the more (or less) frequent predictor. This finding adds to the growing evidence for pseudocontingencies (Fiedler & Freytag, 2004), a framework that stresses base-rate influences on contingency learning.     

热手谬误？赌徒谬误？ ——随机序列知觉中近因效应的格式塔现象研究

通过两个实验来探讨随机序列中的近因效应。在实验1中,采用传统实验范式,让被试进行一系列的抛掷硬币结果的猜测并给予反馈,结果发现：（1）在最近连续几次硬币呈现的结果不同时,人们通常把各个结果分别作为独立的单元来看待,大部分情况下做出随机性的预期;（2）在最近连续几次硬币呈现的结果相同时,人们通常把连续几次相同的结果作为一个认知单元来看待,在最近猜测对错两种情况下分别出现了截然相反的两种近因效应。当最近1次猜对时,对下一结果的预期出现正近因效应即热手谬误,但是最近几次连续猜对时谬误减少乃至消失;当最近1次猜错时,对下一结果的预期出现负近因效应即赌徒谬误,并且最近几次连续猜错时负近因效应并未受到太大影响。实验2在实验1范式的基础上,把硬币抛掷的结果人为分组,发现被试对每一组的第一个结果做出预期时,实验1中的各种效应均消失,该现象支持关于随机序列知觉的“格式塔理论”。     

Exploring the conjunction fallacy within a category learning framework

The literature presents two major theories on the cause of the conjunction fallacy. The first attributes the conjunction fallacy to the representativeness heuristic. The second suggests that the conjunction fallacy is caused by people combining p(A) and p(B) into p(A&B) in an inappropriate manner. These two theories were contrasted in two category‐learning experiments. As predicted by the latter theory, data showed that participants that could assess p(A&B) directly made fewer conjunction fallacies than participants who had to compute p(A) and p(B) separately and then combine them into p(A&B). Least conjunction fallacies were observed in the cases where the representativeness heuristic was applicable. Overall, data showed that an inability to appropriately combine probabilities is one of the key cognitive mechanisms behind the conjunction fallacy. Copyright © 2008 John Wiley & Sons, Ltd.     

The social implications of planning: How public predictions bias future plans

The planning fallacy, or tendency to underestimate how long a task will take to complete, is a robust phenomenon. Although several explanations have been offered (e.g., ignoring underestimations made in the past), we hypothesized that self-presentation concerns may also contribute to the bias, and that this effect may be exacerbated by a previous failure to complete a task on time. Half of our sample (n = 85) were led to believe that they failed to complete an initial task on time, and half were not. Predictions were then made for time to complete a second task either verbally to a familiar experimenter (high self-presentation) or anonymously (low self-presentation). Although verbal predictions exhibited the typical planning fallacy, anonymous predictions did not. Additionally, verbal predictions were less accurate, that is, less correlated with actual completion times, than were anonymous predictions. There was no significant difference in the bias as a result of the failure manipulation, nor was there an interaction between the self-presentation and failure conditions.     

An account of subjective probability judgment for joint events: Conjunctive and disjunctive

Probability judgment is a vital part of many aspects of everyday life. In the present paper, we present a new theory of the way in which individuals produce probability estimates for joint events: conjunctive and disjunctive. We propose that a majority of individuals produce conjunctive (disjunctive) estimates by making a quasi‐random adjustment, positive or negative, from the less (more) likely component probability with the other component playing no obvious role. In two studies, we produce evidence supporting propositions that follow from our theory. First, the component probabilities do appear to play the distinct roles we propose in determining the joint event probabilities. Second, contrary to probability theory and other accounts of probability judgment, we show that the conjunctive‐less likely probability difference is unrelated to the more likely disjunctive probability difference (in normative theory these quantities are identical). In conclusion, while violating the norms of probability judgment, we argue that estimates produced in the manner we propose will be close enough to the normative values especially given the changing nature of the external environment and the incomplete nature of available information.     

Lax monitoring versus logical intuition: The determinants of confidence in conjunction fallacy

The general assumption that people fail to notice discrepancy between their answer and the normative answer in the conjunction fallacy task has been challenged by the theory of Logical Intuition. This theory suggests that people can detect the conflict between the heuristic and normative answers even if they do not always manage to inhibit their intuitive choice. This theory gained support from the finding that people report lower levels of confidence in their choice after they commit the conjunction fallacy compared to when their answer is not in conflict with logic. In four experiments we asked the participants to give probability estimations to the options of the conflict and no-conflict versions of the tasks in the original set-up of the experiment or in a three-option design. We found that participants perceive probabilities for the options of the conflict version less similar than for the no-conflict version. As people are less confident when choosing between more similar options, this similarity difference is proposed to serve as a mediator in the task in a way that the conflict and no-conflict conditions have their effects on confidence ratings through manipulating the similarity of the answer options.     

Genes and Citizens: Can Moral Philosophy Learn from Evolutionary Biology?

The claim that moral philosophers have something to learn from recent neo-Darwinian theory cannot be sustained – at least, not in the case of the three theses characteristic of the latter on which I concentrate. The first thesis, reductionism, is open to some serious, and familiar, objections. Neo-Darwinism can escape those objections only by weakening its position to a point at which it can no longer be described as distinctively reductionist. The second, atavism, mistakenly attempts to generalise from the apparent persistence of` ‘vestigial’ behaviour patterns. Third, neo-Darwinists are frequently guilty of a number of confusions over the relation between fact and value. In conclusion, I point out that neo-Darwinism derives a certain ideological dynamic from the misleading supposition that patterns of explanation which succeed in one area necessarily apply in others. This revised version was published online in August 2006 with corrections to the Cover Date.