Background beliefs in Bayesian inference

We report five experiments in which the role of background beliefs in social judgments of posterior probability was investigated. From a Bayesian perspective, people should combine prior probabilities (or base rates) and diagnostic evidence with equal weighting, although previous research shows that base rates are often underweighted. These experiments were designed so that either piece of information was supplied either by personal beliefs or by presented statistics, and regression analyses were performed on individual participants to assess the relative influence of information. We found that both prior probabilities and diagnostic information significantly influenced judgments, whether supplied by beliefs or by statistical information, but that belief-based information tended to dominate the judgments made.     

Category learning with a goal: how goals constrain conceptual acquisition

A novel task was used to examine the roles that goals play in concept acquisition. In Experiment 1, we varied the type of interaction, and thus the task goal, of participants working in a novel domain. Following those interactions, participant responses showed that they had organized their knowledge in terms of goal-relevant features. Using a variation of the same methodology, Experiment 2 provided evidence that the goal relevance also played a role in how the participants structured their knowledge of the items, specifically what information about the items was associated with differentiating the categories encountered. The results suggest that the goals not only highlighted particular features, they determined the centrality of those features in the conceptual knowledge. We discuss the results in terms of the goal-framework hypothesis; the idea that goals structure information and provide coherence to the acquired concepts. We discuss how this approach informs category learning research.     

Physician Bayesian updating from personal beliefs about the base rate and likelihood ratio

Whether humans can accurately make decisions in line with Bayes’ rule has been one of the most important yet contentious topics in cognitive psychology. Though a number of paradigms have been used for studying Bayesian updating, rarely have subjects been allowed to use their own preexisting beliefs about the prior and the likelihood. A study is reported in which physicians judged the posttest probability of a diagnosis for a patient vignette after receiving a test result, and the physicians’ posttest judgments were compared to the normative posttest calculated from their own beliefs in the sensitivity and false positive rate of the test (likelihood ratio) and prior probability of the diagnosis. On the one hand, the posttest judgments were strongly related to the physicians’ beliefs about both the prior probability as well as the likelihood ratio, and the priors were used considerably more strongly than in previous research. On the other hand, both the prior and the likelihoods were still not used quite as much as they should have been, and there was evidence of other nonnormative aspects to the updating, such as updating independent of the likelihood beliefs. By focusing on how physicians use their own prior beliefs for Bayesian updating, this study provides insight into how well experts perform probabilistic inference in settings in which they rely upon their own prior beliefs rather than experimenter-provided cues. It suggests that there is reason to be optimistic about experts’ abilities, but that there is still considerable need for improvement.     

People are more likely to be insincere when they are more likely to accidentally tell the truth

Although people lie often, and mostly for self-serving reasons, they do not lie as much as they could. The “fudge factor” hypothesis suggests that one reason for people not to lie is that they do not wish to self-identify as liars. Accordingly, self-serving lies should be more likely when they are less obvious to the liars themselves. Here we show that the likelihood of self-serving lies increases with the probability of accidentally telling the truth. Players in our game could transmit sincere or insincere recommendations to their competitors. In line with the fudge factor hypothesis, players lied when their beliefs were based on flimsy evidence and did not lie when their beliefs were based on solid evidence. This is the first demonstration of a new moral hypocrisy paradox: People are more likely to be insincere when they are more likely to accidentally tell the truth.     

The power of causal beliefs and conflicting evidence on causal judgments and decision making

In two experiments, we investigated the relative impact of causal beliefs and empirical evidence on both decision making and causal judgments, and whether this relative impact could be altered by previous experience. Participants had to decide which of two alternatives would attain a higher outcome on the basis of four cues. After completing the decision task, they were asked to estimate to what extent each cue was a reliable cause of the outcome. Participants were provided with instructions that causally related two of the cues to the outcome, whereas they received neutral information about the other two cues. Two of the four cues—a causal and a neutral cue—had high validity and were both generative. The remaining two cues had low validity, and were generative in Experiment 1, but almost not related to the outcome in Experiment 2. Selected groups of participants in both experiments received pre-training with either causal or neutral cues, or no pre-training was provided. Results revealed that the impact of causal beliefs and empirical evidence depends on both the experienced pre-training and cue validity. When all cues were generative and participants received pre-training with causal cues, they mostly relied on their causal beliefs, whereas they relied on empirical evidence when they received pre-training with neutral cues. In contrast, when some of the cues were almost not related to the outcome, participants’ responses were primarily influenced by validity and—to a lesser extent—by causal beliefs. In either case, however, the influence of causal beliefs was higher in causal judgments than in decision making. While current theoretical approaches in causal learning focus either on the effect of causal beliefs or empirical evidence, the present research shows that both factors are required to explain the flexibility involved in human inferences.     

The meaning of malingering data: further applications of Bayes' theorem

A previous Behavioral Sciences and the Law article (Mossman & Hart, 1996) asserted that information from malingering tests is best conceptualized using Bayes' theorem, and that courts therefore deserve Bayesian interpretations when mental health professionals present evidence about malingering. Mossman and Hart gave several examples of estimated Bayesian posterior probabilities, but they did not systematically address how one constructs confidence intervals for these estimates. This article explains how the usually imperfect nature of humanly created diagnostic tests mandates Bayesian interpretations of test results, and describes methods for generating confidence intervals for posterior probabilities. Sample calculations show that Bayesian reasoning is quite feasible and would not require investigators to expend unusual efforts when constructing and validating malingering instruments. Bayesian interpretations most accurately capture what malingering tests do: provide information that alters one's beliefs about the likelihood of malingering.     

Within-subject consistency and between-subject variability in Bayesian reasoning strategies

It is well known that people tend to perform poorly when asked to determine a posterior probability on the basis of a base rate, true positive rate, and false positive rate. The present experiments assessed the extent to which individual participants nevertheless adopt consistent strategies in these Bayesian reasoning problems, and investigated the nature of these strategies. In two experiments, one laboratory-based and one internet-based, each participant completed 36 problems with factorially manipulated probabilities. Many participants applied consistent strategies involving use of only one of the three probabilities provided in the problem, or additive combination of two of the probabilities. There was, however, substantial variability across participants in which probabilities were taken into account. In the laboratory experiment, participants’ eye movements were tracked as they read the problems. There was evidence of a relationship between information use and attention to a source of information. Participants’ self-assessments of their performance, however, revealed little confidence that the strategies they applied were actually correct. These results suggest that the hypothesis of base rate neglect actually underestimates people’s difficulty with Bayesian reasoning, but also suggest that participants are aware of their ignorance.     

Preference modulates smelling behaviour in olfactory decision tasks

When people are shown a pair of images and asked to identify which one is more attractive, their gaze shifts to the image they will eventually choose, prior to making the decision. Many researchers have examined the relationship between this gaze bias and decision processes, but not the relationships between other sensory modalities and decision processes. This study examined behaviour in relation to olfactory decision tasks. In accordance with the concept of gaze bias, the likelihood of participants smelling the item they eventually chose immediately before the decision was greater when they were instructed to identify an item that was more, versus less, favoured. The likelihood of smelling the item that was eventually chosen last was also greater than chance when participants were instructed to identify the more masculine item. These results suggest that a bias to sample a chosen item last is a common phenomenon regardless of sensory modality.     

Insensitivity and oversensitivity to answer diagnosticity in hypothesis testing

Two experiments examined how people perceive the diagnosticity of different answers (“yes” and “no”) to the same question. We manipulated whether the “yes” and the “no” answers conveyed the same amount of information or not, as well as the presentation format of the probabilities of the features inquired about. In Experiment 1, participants were presented with only the percentages of occurrence of the features, which most straightforwardly apply to the diagnosticity of “yes” answers. In Experiment 2, participants received in addition the percentages of the absence of features, which serve to assess the diagnosticity of “no” answers. Consistent with previous studies, we found that participants underestimated the difference in the diagnosticity conveyed by different answers to the same question. However, participants' insensitivity was greater when the normative (Bayesian) diagnosticity of the “no” answer was higher than that of the “yes” answer. We also found oversensitivity to answer diagnosticity, whereby participants valued as differentially diagnostic two answers that were normatively equal in terms of their diagnosticity. Presenting to participants the percentages of occurrence of the features inquired about together with their complements increased their sensitivity to the diagnosticity of answers. We discuss the implications of these findings for confirmation bias in hypothesis testing.     

Maintaining Positive Self-Evaluations: Reducing Attention to Diagnostic but Unfavorable Social Comparison Information When General Self-Regard Is Salient

We predicted that when (1) people are faced with diagnostic but personally challenging social comparison information in a domain, and (2) their self-regard is salient, they will be less likely to use the comparison information when judging their standing in the domain (making the judgment less inductive). Participants in Study 1 estimated their standing on risk factors for two health problems, and some did so after their self-regard was made salient. Moreover, some received information (about their peers' standing on these risk factors) that challenged participants' self-serving comparative beliefs. As expected, estimates of personal risk factor standing among high self-regard salience/comparison information participants were less correlated with similar estimates collected 2 months earlier, suggesting the estimates had become less inductive. There was also tentative evidence that, in this condition, self-esteem played a greater role in constructing these estimates. In Study 2, participants were led to believe that their comparative standing on risk factors was better than it actually was, and in this case, they were more likely to use this information when making self-judgments about their personal risk. Evidently, the extent to which people use diagnostic comparison information inductively when making self-inferences depends on the favorability of that information.     

Strategies of clinical hypothesis testing

This research examines whether Psychology students, when they test clinical hypotheses, follow either confirmatory or disconfirmatory reasoning strategies. Two hundred and six psychology students, divided in four groups, participated. One group received information about the probability that the hypothesis was correct by means of verbal labels, and another group, by means of numerical expressions. An additional group received the information that getting a precise diagnosis was clinically important. In a last group, diagnostic tests allowed them to increase certainty about the hypothesis. Results show a partial use of confirmatory strategies because, although participants did not seek confirming information, they indeed avoided collecting disconfirming information. When the information increased certainty about the hypothesis, confirmatory strategies became more likely. Neither the increase in the task importance nor the numerical expression of the likelihood that the hypothesis was correct seemed to affect the testing strategy used.     

计算机化分类测验终止规则的类别、特点及应用

计算机化分类测验(Computerized Classification Testing, CCT)能够高效地对被试进行分类, 已广泛应用于合格性测验及临床心理学中。作为CCT的重要组成部分, 终止规则决定测验何时停止以及将被试最终划分到何种类别, 因此直接影响测验效率及分类准确率。已有的三大类终止规则(似然比规则、贝叶斯决策理论规则及置信区间规则)的核心思想分别为构造假设检验、设计损失函数和比较置信区间相对位置。同时, 在不同测验情境下, CCT的终止规则发展出不同的具体形式。未来研究可以继续开发贝叶斯规则、考虑多维多类别情境以及结合作答时间和机器学习算法。针对测验实际需求, 三类终止规则在合格性测验上均有应用潜力, 而临床问卷则倾向应用贝叶斯规则。     

Imagination can create false autobiographical memories

Previous studies have shown that imagining an event can alter autobiographical beliefs. The current study examined whether it can also create false memories. One group of participants imagined a relatively frequent event and received information about an event that never occurs. A second group imagined the nonoccurring event and received information about the frequent event. One week before and again 1 week immediately after the manipulation, participants rated the likelihood that they had experienced each of the two critical events and a series of noncritical events, using the Life Events Inventory. During the last phase, participants were also asked to describe any memories they had for the events. For both events, imagination increased the number of memories reported, as well as beliefs about experiencing the event. These results indicate that imagination can induce false autobiographical memories.     

Rational Inference of Beliefs and Desires From Emotional Expressions

We investigated people's ability to infer others’ mental states from their emotional reactions, manipulating whether agents wanted, expected, and caused an outcome. Participants recovered agents’ desires throughout. When the agent observed, but did not cause the outcome, participants’ ability to recover the agent's beliefs depended on the evidence they got (i.e., her reaction only to the actual outcome or to both the expected and actual outcomes; Experiments 1 and 2). When the agent caused the event, participants’ judgments also depended on the probability of the action (Experiments 3 and 4); when actions were improbable given the mental states, people failed to recover the agent's beliefs even when they saw her react to both the anticipated and actual outcomes. A Bayesian model captured human performance throughout (rs ≥ .95), consistent with the proposal that people rationally integrate information about others’ actions and emotional reactions to infer their unobservable mental states.     

Confirming expectations in asymmetric and symmetric social hypothesis testing

This article examines individuals' expectations in a social hypothesis testing task. Participants selected questions from a list to investigate the presence of personality traits in a target individual. They also identified the responses that they expected to receive and the likelihood of the expected responses. The results of two studies indicated that when people asked questions inquiring about the hypothesized traits that did not entail strong a priori beliefs, they expected to find evidence confirming the hypothesis under investigation. These confirming expectations were more pronounced for symmetric questions, in which the diagnosticity and frequency of the expected evidence did not conflict. When the search for information was asymmetric, confirming expectations were diminished, likely as a consequence of either the rareness or low diagnosticity of the hypothesis-confirming outcome. We also discuss the implications of these findings for confirmation bias.     

The emotion-induced memory trade-off: More than an effect of overt attention?

Although it has been suggested that many effects of emotion on memory are attributable to attention, in the present study we addressed the hypothesis that such effects may relate to a number of different factors during encoding or postencoding. One way to look at the effects of emotion on memory is by examining the emotion-induced memory trade-off, whereby enhanced memory for emotional items often comes at the cost of memory for surrounding background information. We present evidence that this trade-off cannot be explained solely by overt attention (measured via eyetracking) directed to the emotional items during encoding. Participants did not devote more overt attention to emotional than to neutral items when those items were selectively remembered (at the expense of their backgrounds). Only when participants were asked to answer true/false questions about the items and the backgrounds—a manipulation designed to affect both overt attention and poststimulus elaboration—was there a reduction in selective emotional item memory due to an increase in background memory. These results indicate that the allocation of overt visual attention during encoding is not sufficient to predict the occurrence of selective item memory for emotional items.     

Evolving informational credentials: the (mis)attribution of believable facts to credible sources

Three studies demonstrate that individuals often rely on a "belief force equals credible source" heuristic to make source judgments, wherein they assume that statements they believe originate from credible sources. In Study 1, participants who were exposed to a statement many times (and hence believed it) were more likely to attribute it to Consumer Reports than to the National Enquirer. In Study 2, participants read a murder investigation article containing evidence against two suspects from credible and noncredible sources. When participants believed a particular suspect to be guilty, they misattributed evidence incriminating that suspect to the high-credibility source. Study 3 demonstrated that this phenomenon occurs because individuals assume their beliefs are true and that true beliefs come from credible sources; when participants were given feedback that their beliefs were incorrect, the relationship between beliefs and source inferences did not occur.     

The role of age and prior beliefs in contingency judgment

This experiment investigated how prior beliefs affect young and older adults' ability to detect differences in objective contingency. Participants received new evidence that the objective contingency between two events was positive, negative, or zero when they believed that there was a positive or negative relationship between events, when they believed that the events were unrelated, and when they had no knowledge of the relationship between the events. They were then asked to estimate the objective contingency and recall the contingency evidence. Beliefs that events were or could be related improved young adults' contingency discrimination. Moreover, these beliefs did not produce biases in young adults' memory for the contingency evidence, but rather affected how they weighted this evidence at judgment. In contrast, these same beliefs did not improve older adults' contingency discrimination, but did produce biases in their memory for the evidence that were similar to those seen in their judgment. These findings are discussed in terms of age-related changes in working memory executive processes that impair older adults' ability to fully evaluate both belief-confirming and disconfirming contingency evidence and update their beliefs with this information.     

Speeded induction under uncertainty: The influence of multiple categories and feature conjunctions

When people are uncertain about the category membership of an item (e.g., Is it a dog or a dingo?), research shows that they tend to rely only on the dominant or most likely category when making inductions (e.g., How likely is it to befriend me?). An exception has been reported using speeded induction judgments where participants appeared to use information from multiple categories to make inductions (Verde, Murphy, &; Ross, 2005). In two speeded induction studies, we found that participants tended to rely on the frequency with which features co-occurred when making feature predictions, independently of category membership. This pattern held whether categories were considered implicitly (Experiment 1) or explicitly (Experiment 2) prior to feature induction. The results converge with other recent work suggesting that people often rely on feature conjunction information, rather than category boundaries, when making inductions under uncertainty.     

Instructional support decreases desirability and initiation of a gratitude intervention

Gratitude interventions tend to be effective at increasing well-being, yet they are not commonly initiated and completed. Prior experimental evidence suggests that provision of social support (i.e., supportive and encouraging statements) increases the effectiveness of positive psychological interventions. The type of support, however, may differentially impact motivation. In the current study, we hypothesized that instructional support (i.e., advice about how to best conduct the intervention) increases the desirability of a gratitude intervention and the probability of initiation. 274 participants received leaflets about a voluntary, web-based gratitude intervention. Half of the participants were randomly assigned to receive instructional support in which they read testimonials on how to best conduct the intervention. Next, participants were asked about utility beliefs, social norm beliefs, self-control beliefs, and intentions to participate in the intervention. Contrary to our hypothesis, provision of instructional support decreased desirability of the gratitude intervention, which indirectly hindered intentions to participate in the intervention. Thus, informing recipients about how to navigate an intervention had a paradoxical effect. It may be more effective to allow participants to recognize and handle intervention challenges on their own.