University of Iowa Honors Theses

Major Department



College of Liberal Arts & Sciences


BA (Bachelor of Arts)

Session and Year of Graduation

Spring 2018

Honors Major Advisor

Toby Mordkoff

Thesis Mentor

Paul Windschitl


People’s desires for an outcome might influence their optimism that the outcome will occur. This is called the desirability bias, or the wishful-thinking effect. The desirability bias occurs when people’s expectations or hopes for an outcome override objectivity when making a prediction about an event. While many studies have shown a desirability bias when asking for dichotomous predictions, few studies have measured how changing the metric influences predictions. In the current study, three types of questions were asked to measure participants’ predictions of the outcome of an endurance race, where participants were assigned one of two competitors. Participants were told if their assigned athlete won the race they would receive a candy bar. In a between-subjects design, participants answered either a dichotomous prediction, a dichotomous likelihood judgment, or a continuous likelihood judgment. We found evidence that the strength of the desirability bias varied between types of questions asked, specifically that there was no desirability bias in continuous likelihood judgments and more desirability bias in the dichotomous prediction condition. This research suggests that the wording of a question has a large impact on conclusions about the desirability bias, which has implications for both scientific research and everyday decision-making.


desirability bias, metric

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Copyright © 2018 Mark Biangmano