I supervise scientific course theses on the undergraduate and graduate levels.

A selection from Stockholm University publication database

• Biased judgments of the effects of speed change on travel time, fuel consumption and braking

  2021. Ola Svenson. Transportation Research Part F 78, 398-409

  Article

  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.

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• On the human inability to process inverse variables in intuitive judgments

  2020. Ola Svenson, Anna Borg. Journal of Cognitive Psychology 32 (3), 344-355

  Article

  The time loss bias describes overestimation of time lost after speed decreases from high speeds and underestimations after decreases from low driving speeds. Participants judged the speed decrease from one speed (e.g. 130 km/h) that would give the same time loss as a decrease from another speed (e.g. from 40 to 30 km/h). We carried out descriptive spectral analyses of distributions of judgments for each problem. Each distribution peak was associated with a judgment rule. The first study found two different judgment processes both leading to the time loss bias: a Difference process rule used for 20% and a Ratio rule used for 31% of the judgments. The correct rule applied to 10% of the judgments. The second study added verbal protocols. The results showed that the Ratio rule was most common (41%) followed by the Difference (12%) and correct (8%) rules. Verbal reports supported these results.

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• Without a mask

  2020. Ola Svenson (et al.). Judgment and decision making 15 (6), 881-888

  Article

  In order to minimize the risk of infection during the Covid-19 pandemic, people are recommended to keep interpersonal distance (e.g., 1 m, 2 m, 6 feet), wash their hands frequently, limit social contacts and sometimes to wear a face mask. We investigated how people judge the protective effect of interpersonal distance against the Corona virus. The REM model, based on earlier empirical studies, describes how a person’s virus exposure decreases with the square of the distance to another person emitting a virus in a face to face situation. In a comparison with model predictions, most participants underestimated the protective effect of moving further away from another person. Correspondingly, most participants were not aware of how much their exposure would increase if they moved closer to the other person. Spectral analysis of judgments showed that a linear ratio model with the independent variable = (initial distance)/(distance to which a person moves) was the most frequently used judgment rule. It leads to insensitivity to change in exposure compared with the REM model. The present study indicated a need for information about the effects of keeping interpersonal distance and about the importance of virus carrying aerosols in environments with insufficient air ventilation. Longer conversations emitting aerosols in a closed environment may lead to ambient concentrations of aerosols in the air that no distance can compensate for. The results of the study are important for risk communications in countries where people do not wear a mask and when authorities consider removal of a recommendation or a requirement to wear a face mask.

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• Forskning med start i perception och psykofysik under Gösta Ekman

  2020. Ola Svenson. Historien om svensk psykologisk forskning, 107-118

  Chapter

  Kapitlet beskriver hur en forskare som doktorerade med Gösta Ekman som handledare och psykofysiken som bas fortsatt som forskare inom kognitionspsykologi, beslutsfattande, riskanalys, trafik- och kärnkraftsäkerhet.

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• Verbal reports and decision process analysis

  2019. Rob Ranyard, Ola Svenson. A handbook of process tracing methods

  Chapter

  This chapter takes a broader look at the use of verbal data in contemporary decision process research. We examine a range of approaches to the elicitation and analysis of verbal reports with the purposes of both describing decision processes and testing theories about them. We recommend and illustrate good practice, thereby providing researchers with the means to make good research design decisions. We define a decision process as a transformation of a structure over time. A decision maker’s mental representation of a decision problem is such a structure, one that includes both cognitive and affective components. Decision problems can be represented in many different ways. For example, decision alternatives can be represented either holistically, or by the attractiveness of different cues, or by arguments for or against the alternatives. Fundamental to process theories is the notion that mental representations can change from the beginning of a decision process until the decision is made, and can continue to change after the decision. These transformations of decision representations are brought about by processes, or operations, defined by a process model or theory, such as the elementary information processes (EIPs).

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• Different heuristics and same bias

  2018. Ola Svenson, Nichel Gonzalez, Gabriella Eriksson. Judgment and decision making 13 (5), 401-412

  Article

  We used correlation and spectral analyses to investigate the cognitive structures and processes producing biased judgments. We used 5 different sets of driving problems to exemplify problems that trigger biases, specifically: (1) underestimation of the impact of occasional slow speeds on mean speed judgments, (2) overestimation of braking capacity after a speed increase, (3) the time saving bias (overestimation of the time saved by increasing a high speed further, and underestimation of time saved when increasing a low speed), (4) underestimation of increase of fatal accident risk when speed is increased, and (5) underestimation of the increase of stopping distance when speed is increased. The results verified the predicted biases. A correlation analysis found no strong links between biases; only accident risk and stopping distance biases were correlated significantly. Spectral analysis of judgments was used to identify different decision rules. Most participants were consistent in their use of a single rule within a problem set with the same bias. The participants used difference, average, weighed average and ratio rules, all producing biased judgments. Among the rules, difference rules were used most frequently across the different biases. We found no personal consistency in the rules used across problem sets. The complexity of rules varied across problem sets for most participants.

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• Information about expert decision and post-decision distortion of facts of own decision

  2018. Ola Svenson (et al.). Scandinavian Journal of Psychology 59 (2), 127-134

  Article

  Cognitive representations of decision problems are dynamic. During and after a decision, evaluations and representations of facts change to support the decision made by a decision maker her- or himself (Svenson, 2003). We investigated post-decision distortion of facts (consolidation). Participants were given vignettes with facts about two terminally ill patients, only one of whom could be given lifesaving surgery. In Study 1, contrary to the prediction, the results showed that facts were distorted after a decision both by participants who were responsible for the decisions themselves and when doctors had made the decision. In Study 2 we investigated the influence of knowledge about expert decisions on a participant's own decision and post-decisional distortion of facts. Facts were significantly more distorted when the participant's decision agreed with an expert's decision than when the participant and expert decisions disagreed. The findings imply that knowledge about experts' decisions can distort memories of facts and therefore may obstruct rational analyses of earlier decisions. This is particularly important when a decision made by a person, who is assumed to be an expert, makes a decision that is biased or wrong.

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• Mental models of driving and speed

  2017. Ola Svenson, Gabriella Eriksson. Transport reviews 37 (5), 653-666

  Article

  This paper provides a review of research performed by Svenson with colleagues and others work on mental models and their practical implications. Mental models describe how people perceive and think about the world including covariances and relationships between different variables, such as driving speed and time. Research on mental models has detected the time-saving bias [Svenson, O. (1970). A functional measurement approach to intuitive estimation as exemplified by estimated time savings. Journal of Experimental Psychology, 86, 204-210]. It means that drivers relatively overestimate the time that can be saved by increasing speed from an already high speed, for example, 90-130km/h, and underestimate the time that can be saved by increasing speed from a low speed, for example, 30-45km/h. In congruence with this finding, mean speed judgments and perceptions of mean speeds are also biased and higher speeds given too much weight and low speeds too little weight in comparison with objective reality. Replacing or adding a new speedometer in the car showing min per km eliminated or weakened the time-saving bias. Information about braking distances at different speeds did not improve overoptimistic judgments of braking capacity, but information about collision speed with an object suddenly appearing on the road did improve judgments of braking capacity. This is relevant to drivers, politicians and traffic regulators.

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• Speed reductions and judgments of travel time loss

  2017. Ola Svenson, Daniëlle Treurniet. Transportation Research Part F 51, 145-153

  Article

  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.

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• We Distort Memories of Other’s Decisions, and Other’s Decisions Distort Memories of What We Decided

  2017. Torun Lindholm, Amina Memon, Ola Svenson.

  Conference

  Research shows that after making a decision, people often distort the memory of the decision alternatives towards greater coherence with the chosen alternative. Given the pivotal role of sharing cognitive representations of reality with others, it seems reasonable that such decision consolidation may extend beyond decisions made by the individual him-/herself. The current research explores how people consolidate their own and another person’s decisions. Moreover, we examine how information about another person’s decisions affects an individual’s memory of his/her own decision. In Study 1 we presented participants with a medical case scenario in which one of two patients should be prioritized for surgery. They were given facts about the patients (e.g., probability of surviving surgery), and either decided themselves whom to prioritize, or were told that a physician made the decision. When later reproducing the facts from memory, participants distorted memories of facts to become more supportive both of their own and of the doctor’s choice. Study 2 investigated how feedback of other’s decisions affect people’s memory for their own decisions. Participants decided whether a physician should comply or not to the request of a terminally ill patient who asked for help to committ suicide. After making their decision, participants were informed that a majority or a minority had chosen the same alternative. When the patient was an in-group member participants consolidated their own decision more when receiving minority, rather than majority feedback. This reversed for decisions on out-group member. Results suggest important social psychological motivations and moderators of decision consolidation strategies.

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• Social influences on dissonance reduction in medical decision making

  2016. Torun Lindholm, Amina Memon, Ola Svenson. Book of abstracts, 28-28

  Conference

  Two studies investigated social influences on dissonance reduction in medical decision making. Study 1 compared decision-consistent biases when individuals freely made-, or when another person made the decision. Participants read a scenario in which one of two patients should be prioritized for surgery. Facts about the patients were given on counter-balanced scales. Participants decided themselves whom to prioritize, or were told that a physician made the decision, and then reproduced the facts from memory. When choosing freely, participants distorted memories of facts to become more supportive of the choice. This effect was evident, albeit reduced, when the decision was made by a physician.

  Study 2 investigated majority/minority feedback effects on dissonance reduction for decisions concerning ingroup or outgroup members. Swedish participants decided whether a physician should comply or not to the request of a terminally ill patient, with a Swedish or a Turkish name, who asked for help to commit suicide. After making their decision, participants were informed that a majority or a minority had chosen the same alternative. Decisions about an in-group member were consolidated more if participants received minority, than majority feedback. This reversed for decisions on out-group member. Results suggest important social moderators of dissonance reduction strategies.

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• Regulation of Experienced and Anticipated Regret in Daily Decision Making

  2016. Pär Bjälkebring (et al.). Emotion 16 (3), 381-386

  Article

  Decisions were sampled from 108 participants during 8 days using a web-based diary method. Each day participants rated experienced regret for a decision made, as well as forecasted regret for a decision to be made. Participants also indicated to what extent they used different strategies to prevent or regulate regret. Participants regretted 30% of decisions and forecasted regret in 70% of future decisions, indicating both that regret is relatively prevalent in daily decisions but also that experienced regret was less frequent than forecasted regret. In addition, a number of decision-specific regulation and prevention strategies were successfully used by the participants to minimize regret and negative emotions in daily decision making. Overall, these results suggest that regulation and prevention of regret are important strategies in many of our daily decisions.

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• Towards a framework for human judgements of quantitative information

  2016. Ola Svenson. Journal of Cognitive Psychology 28 (7), 884-898

  Article

  This contribution presents a review and a theoretical process framework for human intuitive numerical judgments based on numerical information, The NJP model. The model is descriptive and includes one or several of the following stages, each consisting of information processing and solution strategies (1) problem readings (2) recognitions, (3) associations, (4) similarity assessments, (5) problem interpretations, (6) computations, (7) marker nominations, (8) start value selections and (9) adjustments. three main types of strategies are used separately, in sequence or simultaneously with others in and across stages: (i) Associative strategies, e.g., an answer is retrieved immediately, (ii) Computational strategies, different algorithms are applied to the information and (iii) Analogue strategies, visual analogue representations, e.g., anchoring and adjustment. The paper concludes that a generic model of intuitive judgments will inspire further studies of the psychological processes activated when a judge makes an intuitive numerical judgment.

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Show all publications by Ola Svenson at Stockholm University