News Release 

People view rationality and reasonableness as distinct principles of judgment

University of Waterloo

When it comes to making sound judgements, most people understand and distinguish that being rational is self-serving and being reasonable is fair and balanced, finds new research from the University of Waterloo.

The study is the first systematic attempt to explore what people consider to be sound judgment and whether they understand rationality and reasonableness along the lines advocated by experts in economics, law, and other social scientists.

"Our results show that laypeople grasp economists' view of rationality, yet they favour socially pragmatic reasonableness as a separate standard of judgment," said Igor Grossmann, professor of psychology at Waterloo and lead author on the study.

To understand how the general public views rationality and reasonableness, Grossmann collaborated with colleagues in Canada and Pakistan to examine impressions of rational and reasonable persons and actions.

"The concept of rationality that we found lay people have corresponds to economists' definition, which emphasizes abstract logic and pursuit of self-interest," said Grossmann. "We also found people tend to uphold a distinct standard of reasonableness that corresponds to philosophical traditions encouraging context-specific balance of self-interest with fairness."

The researchers analyzed the use of the terms "rational" and "reasonable" in web-based news, US Supreme Court Opinions, scripts of popular soap operas, and Google books covering languages spoken in 1/6 of the world today. They quantified common characteristics attributed to rational and reasonable persons.

Researchers also surveyed laypeople's common stereotypes of rational and reasonable agents, and performed 13 experiments contrasting cooperative and self-serving behavior in economic games. Experiments involved participants in North America as well as urban and rural Pakistan.

"Rationality and reasonableness lead people to different conclusions about what constitutes sound judgment in dilemmas that pit self-interest against fairness," said Richard Eibach, professor of psychology at Waterloo and a co-author of the study. "People view rationality as absolute and preference-maximizing, whereas they view reasonableness as paying attention to particulars and fairness."

Researchers also found that people use rational and reasonable standards of judgment strategically, favouring a rational person to represent their side in economic and social disputes, but choosing a reasonable person to represent the other side.

"These findings cast prior demonstrations of people's irrationality in a new light," says Grossmann. "People may choose to be irrational when it violates their preferred standard of reasonable, socially-conscious behavior."

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Folk standards of sound judgment: Rationality Versus Reasonableness by Grossmann and Eibach, along with collaborators Jacklyn Koyama (University of Toronto) and Qaisar B. Sahi (Shaheed Zulfikar Ali Bhutto Institute of Science and Technology in Pakistan) was published in the journal Science Advances. The research was funded in part by the Social Sciences and Humanities Research Council of Canada, the Ontario Early Researcher Award, and the Templeton Pathways to Character Award.

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