Biased judgments of the effects of speed change on travel time,fuel consumption and braking: Individual differences in the use of simplifying rules producing the same biases

The main purpose of this study was to identify different cognitive rules that lead to a particular judgment bias. To fulfill this purpose, a new method Spectral analysis was introduced and applied. Participants judged time saved by driving faster, fuel saved by replacing a car and braking capacity at different speeds. These problems invite the time saving bias (e.g., time saved from speed increases at higher speeds overestimated), the miles per gallon, MPG illusion (misjudgment of fuel saved by replacing a car) and the braking capacity bias (overestimation of braking capacity after speed increase). The average results replicated the biases. Spectral analysis of individual participants and problems showed that a speed difference rule explained about half of the time saving judgments and about three fourth of the MPG judgments. A difference between speeds rule described about one third of the biased braking judgments and a ratio/proportion rule about one fifth of the time saving and MPG judgments. All rules give biased judgments in all three domains. The paper ends with a discussion of hierarchies of cognitive rules, applications of the results, and how to mitigate or avoid the biases and the risks associated with the biases.     

Speed reductions and judgments of travel time loss: Biases and debiasing

Priority decisions concerning maintenance or reconstruction of roads are made with the aim of road improvements with as little traffic disturbance and time loss as possible. However, it cannot be avoided that speed will be reduced and travel time increased during the time of construction. The present study shows how intuitive judgments of travel time losses are biased in a way similar to the times saving bias (Svenson, 2008), but not perfectly corresponding to that bias. This means that when speed is decreased from a slow speed <50 km/h, the time loss is underestimated and when speed is decreased from a high speed >80 km/h it is overestimated. Also, drivers, politicians and policy makers who do not make exact calculations are likely victims of the time loss bias. The time loss bias was weakened but not eliminated by a debiasing instruction including mathematical computations of travel times. When driving speed restrictions are implemented, in particular on fast motorways, it is necessary to consider and counteract the time loss bias and inform the public. This can be done, for example, in communications about travel time facts, by information in driver training and by mounting temporary road signs informing about the average travel time prolongation due to a road work.     

Judgments of mean speed and predictions of route choice

How are driving speeds integrated when speeds vary along a route? In a first study, we examined heuristic processes used in judgments of mean speed when the mean speeds on parts of the trip varied. The judgments deviated systematically from objective mean speeds because the distances driven at different speeds were given more weight than travel time spent on the different distances. The second study showed that when there was a 10–15 min pause during a travel the effect on the mean speed decrease was underestimated for driving speeds of 90 km/h and higher. In the third study, the objective mean speeds and the subjective biased mean speed judgments were used to predict choices between routes with different speed limits. The results showed that subjective judgments predicted decisions to maximize mean speed significantly better than objective mean speeds. Finally, some applied and basic research implications of the results were discussed.     

Decisions among time saving options: when intuition is strong and wrong

When people judge the time that can be saved by increasing the speed of an activity, they are often victims of a time saving bias. That is, they overestimate the time that can be saved by increasing the speed. Judgments of time savings following speed increase when driving follow the Proportion heuristic [Svenson, O. (1970). A functional measurement approach to intuitive estimation as exemplified by estimated time savings. Journal of Experimental Psychology, 86, 204-210]. In a choice between time saving options, this heuristic simplifies to the Ratio rule. The first study tested this rule and found that the Ratio rule predicted incorrect decisions when planning to save traveling time in road traffic. The second study showed that the time saving bias was also present in planning of health care; to specify, in decisions about which one of two clinics to reorganize to save more of the doctors' time for personal contacts with patients. To further test the Ratio rule, Study 3 used a matching procedure in which two decision alternatives were made equal by the participants. The results supported the Ratio rule. Practical implications of the results are discussed including the Planning fallacy. In conclusion, the present set of studies have illustrated a time saving bias and provided evidence explaining why people make systematic errors when judging and deciding about time saved following a speed increase.     

A retrieval-based approach to eliminating hindsight bias

Individuals exhibit hindsight bias when they are unable to recall their original responses to novel questions after correct answers are provided to them. Prior studies have eliminated hindsight bias by modifying the conditions under which original judgments or correct answers are encoded. Here, we explored whether hindsight bias can be eliminated by manipulating the conditions that hold at retrieval. Our retrieval-based approach predicts that if the conditions at retrieval enable sufficient discrimination of memory representations of original judgments from memory representations of correct answers, then hindsight bias will be reduced or eliminated. Experiment 1 used the standard memory design to replicate the hindsight bias effect in middle-school students. Experiments 2 and 3 modified the retrieval phase of this design, instructing participants beforehand that they would be recalling both their original judgments and the correct answers. As predicted, this enabled participants to form compound retrieval cues that discriminated original judgment traces from correct answer traces, and eliminated hindsight bias. Experiment 4 found that when participants were not instructed beforehand that they would be making both recalls, they did not form discriminating retrieval cues, and hindsight bias returned. These experiments delineate the retrieval conditions that produce—and fail to produce—hindsight bias.     

How to nudge drivers to reduce speed: The case of the left-digit effect

To decrease the negative consequences of a road crash, even a small reduction in driving speeds can make a significant difference. We examined the possible application of the left-digit effect as a nudge to reduce road speed. In the marketing field, this effect is based on reporting price tags that are characterized by a low leftmost number and a high rightmost number (e.g., a price tag of €14.99 rather than €15.00). We applied the same strategy to improve road safety. Participants were college students (43.75% female, mean age = 24.06 years in Study 1; 50% female, mean age = 23.53 years in Study 2) who were asked to drive in a simulator on a route that had both usual unmodified road signs (e.g., 50 km/h) and the same road signs increased or decreased by one unit (e.g., 49, 51 km/h). We compared the average median speeds in road segments with unmodified road signs with those in road segments with the corresponding modified signs. The average median speeds in the presence of a sign modified by the reduction of 1 km/h were significantly lower compared with the median average speeds recorded with unmodified signs. We showed that the application of psychological insights can reduce driving speeds and therefore increase road safety.     

短时距估计中刺激物的动态变化效应

用两个实验考查了时距估计中刺激物的动态变化效应。结果发现,刺激物的运动、速度和旋转角度显著地影响着被试的时间判断,刺激物速度的时距延长效应对于较长时距(18s-24s)来说更加明显;运动刺激与较短、较准确的时距判断相关联;旋转角度的减少使得被试低估时距,而旋转角度的增加使得时距估计呈高估倾向。被试在时间估计过程中表现出长时距低估和短时距高估现象,本研究得到的时间估计转换点是11.4s,此点与先前的有关研究基本一致。     

Resolution time and the coding of arithmetic relations on supraliminally different visual extents

Comparison time for pairs of vertical-line stimuli, sufficiently different that they can be errorlessly discriminated with respect to visual extent, was examined as a function of arithmetic relations (physical ratio and difference) on members of the pair. Arithmetic relations are coded very precisely by judgment time: Responses slow as stimulus ratios approach one with difference fixed, and as stimulus differences approach zero with ratio fixed. Most models which assume a simple (Difference or Ratio) resolution rule operating on independent sensations require judgment time to depend on either ratios or on differences but not on both. Further tests showed both an index based on median judgment times and a confusion index based on pairs of observed judgment times, satisfied the requirements for a Positive Difference Structure. One representation of these data, which remains acceptable through all analyses, is a Difference resolution rule operating on sensations determined by a power psychophysical function with β < 1. Specifically, L(x, y) = F{ψ(x) ? ψ(y)} + R, where L(x, y) is the judgment time with the stimulus pair x and y, ψ(x) = Ax^β + C, R is a positive constant, and F is a continuous monotone decreasing function.     

The Prevalence of Metacognitive Routes to Judgment

Metacognitive routes to judgment may be taken more often than suggested by Schwarz (2004). First, judgments that appear to be consistent with a systematic processing account may be based on higher order metacognitive theories. Specifically, individuals’ inferential judgments based on naive theories about retrieval ease may be interpreted to be potentially biased, resulting in an adjustment in the opposite direction of the initial judgment to correct for the bias. Second, whereas favorable attitudes may reflect the positive experience of processing fluency, favorable attitudes may also reflect naive theories at work. When the target (e.g., brand name, logo, etc.) can be more easily processed, the hedonic experience of processing fluency gives rise to more favorable attitudes toward the target. However, when information about the target (e.g., an ad highlighting benefits of the brand) can be more easily processed, individuals may interpret the experience of processing fluency based on naive theory and attribute the experience to the information being more persuasive, resulting in more favorable attitudes toward the target.     

Effects of speed display signs on driving speed at pedestrian crossings on collector streets

This study was designed to evaluate the short- and long-term effects of speed display signs on driving speed at pedestrian crossings in a low-speed (40 km/h) urban environment. Driving speeds were compared 1 week before installation, after installation (1 week; 1 month; 3 months; 5 months) and 1 week after removal. The main results showed that the speed displays decreased the mean speed by 0.5–2.9 km/h, which translates to a 4–22% drop in pedestrian fatality risk. Furthermore, there was a drop in the proportion of speeding vehicles and approaching speed of individual vehicles. The decrease in speed persisted over time, suggesting that speed displays may reduce speeds in the long term. In conclusion, installing speed displays at pedestrian crossings on collector streets reduces driving speeds and could contribute to the safety of pedestrians.     

The accuracy of self-monitoring and its relationship to self-focused attention in dysphoria and clinical depression

The accuracy with which dysphoric (Study 1) and clinically depressed (Study 2) individuals make self-regulatory judgments about their own performance in the absence of external feedback and the extent to which this relates to trait self-focused attention (SFA) were examined. Relative to objective criteria, both dysphoric and depressed participants showed a positive judgment bias, overestimating the number of trials they had performed correctly. Relative to control participants, the dysphoric and depressed groups showed a reduction in the extent of this positive bias in that they judged error trials more accurately and correct trials less accurately. Although the dysphoric and depressed groups both reported elevated trait SFA, this did not correlate significantly with accuracy of self-judgment on the performance-monitoring task. Implications for self-regulation models of depression are discussed.     

Just how comparative are comparative judgments?

Three studies investigate the psychology of comparative judgment, examining the circumstances under which judgments tend to concentrate disproportionately on one of the two elements that underlie the comparison (i.e., focused comparisons). We examine these tendencies at the judgment formation and information retrieval stages by examining judgment content as well as the speed and efficiency with which people make comparisons. The results replicate prior findings of differential weighting, indicating that focusing occurs in the formation stage of comparative judgments. However, focusing is absent in the reaction time data, suggesting that both elements of the comparison are equally accessible when individuals retrieve comparison-relevant information. These findings clarify the process by which people arrive at comparative judgments and demonstrate precisely when focused comparisons occur.     

驾驶员的动态反应时研究

本研究应用DFY-1型动态反应时测试仪,以解放CA10B 型卡车为实验用车,结合日常运输任务,对三种年龄组(20—29岁、30—39岁、40—49岁)的30名驾驶员,在三种车速(静态,30公里/小时及50公里/小时)条件下的反应时、动作时及制动反应时进行了测试。结果表明:车速对驾驶员的反应时及制动反应时有显著影响,而对动作时则无显著影响;驾驶员的年龄对反应时、动作时及制动反应时均无显著影响.本研究结果为加强驾驶员的安全教育与管理,控制车速提供了佐证。更高车速条件下驾驶员的反应时特点尚待进一步研究。     

The truth and bias model of judgment

We present a new model for the general study of how the truth and biases affect human judgment. In the truth and bias model, judgments about the world are pulled by 2 primary forces, the truth force and the bias force, and these 2 forces are interrelated. The truth and bias model differentiates force and value, where the force is the strength of the attraction and the value is the location toward which the judgment is attracted. The model also makes a formal theoretical distinction between bias and moderator variables. Two major classes of biases are discussed: biases that are measured with variables (e.g., assumed similarity) and directional bias, which refers to the extent to which judgments are pulled toward 1 end of the judgment continuum. Moderator variables are conceptualized as variables that affect the accuracy and bias forces but that do not affect judgments directly. We illustrate the model with 4 examples. We discuss the theoretical, empirical, methodological, measurement, and design implications of the model.     

How to explain receptivity to conjunction-fallacy inhibition training: Evidence from the Iowa Gambling Task

Intuitive predictions and judgments under conditions of uncertainty are often mediated by judgment heuristics that sometimes lead to biases. Using the classical conjunction bias example, the present study examines the relationship between receptivity to metacognitive executive training and emotion-based learning ability indexed by Iowa Gambling Task (IGT) performance. After completing a computerised version of the IGT, participants were trained to avoid conjunction bias on a frequency judgment task derived from the works of Tversky and Kahneman. Pre- and post-test performances were assessed via another probability judgment task. Results clearly showed that participants who produced a biased answer despite the experimental training (individual patterns of the biased → biased type) mainly had less emotion-based learning ability in IGT. Better emotion-based learning ability was observed in participants whose response pattern was biased → logical. These findings argue in favour of the capacity of the human mind/brain to overcome reasoning bias when trained under executive programming conditions and as a function of emotional warning sensitivity.     

The Hard–Easy Effect in Subjective Probability Calibration

Four different factors have been used to explain the hard–easy effect in subjective probability judgments, in which calibration goes systematically from over- to underconfidence as task difficulty decreases. The factors are biased judgment, lack of suitable adjustment of response criteria (decision variable partition model), biased choice of stimulus material (ecological model), and random error in judgment (error model). Although there is strong evidence for judgmental bias, it seems unlikely to account fully for the systematic character of the effect. We describe the judgment models that emphasize the other three factors and then present two new experiments and a further analysis of the calibration problem. The findings of these experiments and the analysis support the response criteria approach and indicate that the ecological model, and biased choice of stimulus material, is not correct. Since error by itself cannot fully explain observed underconfidence phenomena, we conclude that the most likely explanation of the hard–easy effect is in terms of response criteria. A simulation of the decision variable partition model shows that its behavior closely matches the observed relation between overconfidence and proportion correct for a large sample of experimental results.     

Causal uncertainty and correction of judgments

We examined whether raising uncertainty about the causes of one’s judgments motivates correction. Specifically, we examined whether activating chronically accessible causal uncertainty (CU) beliefs with a conditional warning about possible bias enhances correction of weather judgments for tropical weather primes and of word frequency judgments for the availability bias. In two studies we showed that activating chronic beliefs led to careful correction of target judgments. Moreover, Study 2 revealed that chronically high-CU individuals who received a conditional warning felt more uncertain than did other participants, but that this uncertainty was suppressed somewhat by adjusting for the bias. Results are discussed in light of recent models of judgment correction (e.g., Wegener & Petty, 1997), and the causal uncertainty model (Weary & Edwards, 1996).     

Anchoring,Familiarity, and Confidence in the Detection of Deception

Anchoring in judgments is the tendency for the final judgment to be biased toward the initial estimate through insufficient adjustment. In the context of the detection of deception, it has been used to explain phenomena such as negative absolute leakage and the truthfulness bias. We examined the influence of order of judgment type on attitude ratings, accuracy, and the truthfulness bias. Receivers of communications should tend to anchor their judgments on the sender's attitudinal position if asked to make attitude judgments first and on the sender's behavior if asked to make truthfulness judgments first. The results partly support these predictions. Negative absolute leakage, accuracy, and the truthfulness bias were not significantly different for those who made attitude judgments before truthfulness judgments. However, results show that accuracy decreased as the session continued and there was no difference in the confidence with which truth and deception judgments were made, but there was a positive relation between confidence and truthfulness bias.     

Note on the rationality of rule-based versus exemplar-based processing in human judgment

This paper reports a study of the relationship between rule- versus exemplar-based processing and criteria for rationality of judgment. Participants made probability judgments in a classification task devised by S. W. Allen and L. R. Brooks (1991). In the exemplar condition, the miscalibration was accounted for by stochastic components of the judgment with a format-dependence effect, implying simultaneous over- and underconfidence depending on the response scale. In the rule condition, there was an overconfidence bias not accounted for by the stochastic components of judgment. In both conditions the participants were additive on average and reasonably transitive, but the larger stochastic component in the exemplar condition produced somewhat larger absolute deviations. The results suggest that exemplar processes are unbiased but more perturbed by stochastic components, while rule-based processes may be more prone to bias.     

Hindsight bias in insight and mathematical problem solving: Evidence of different reconstruction mechanisms for metacognitive versus situational judgments

This article presents two experiments that used insight and mathematical problems to investigate whether different factors would affect hindsight bias on metacognitive and situational judgments. In both studies, participants initially rated their likelihood of solving each problem within a certain amount of time (metacognitive judgments) and rated the importance of each component of the problem for finding the solution (situational judgments). Next, participants attempted to solve each problem. In Experiment 1, all participants were given solution feedback information, but in Experiment 2, participants were not given any solution feedback. After 1 week, participants were asked to recall their original judgments. Hindsight bias was assessed by comparing the initial with the final ratings. Insight problems and math problems showed different patterns of hindsight bias effects on the metacognitive and situational judgments. The results suggest that two competing models of hindsight effects are actually complementary explanations for judgment reconstruction on different types of judgment tasks.