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Two Heads Not Always Better Than One

Two Heads Not Always Better Than OneThe old saying “two heads are better than one” is not always true, according to new research from the University of Pennsylvania’s Wharton School.

“People who make judgments by working with someone else are more confident in those judgments. As a result they take less input from other people,” said psychologist Julia A. Minson, Ph.D., who noted this “myopia wipes out any advantage a pair may have over an individual. The collaborative process itself is the problem.”

To test their hypothesis that confidence born of collaboration takes a toll on the quality of judgment, Minson and her co-researcher asked 252 people to estimate nine quantities related to U.S. geography, demographics, and commerce, either individually or in pairs after discussion.

They were then offered the estimates of other individuals and pairs and allowed to revise their own, so the final estimates could come from the efforts of two to four people.

To sweeten the pot, participants earned a $30 bonus for each of two estimation rounds, but lost $1 for each percentage point their estimate deviated from the correct answer. Individuals also rated their confidence in their judgments.

The researchers found that people working with a partner were more confident in their estimates and significantly less willing to take outside advice. The pairs’ guesses were marginally more accurate than those of the individuals at first.

But after revision, that difference was gone, the researchers note. Even the combined judgments of four people yielded no better results than those of two or three.

Finally, the researchers found that had the pairs yielded to outside input, their estimates would have been significantly more accurate.

Minson says don’t be in a hurry to toss out teamwork. “But since collaboration is expensive and time-consuming, managers should use it efficiently,” she said, noting that a group of 10 is not 10 times better.

“Mathematically, you get the biggest bang from the buck going from one decision-maker to two,” she said. “For each additional person, that benefit drops off in a downward-sloping curve.”

Being aware of the costs of teamwork is important, she added. “If people become aware that collaboration leads to an increase in overconfidence, you can set up ways to mitigate it,” she said. “Teams could be urged to consider and process each others’ inputs more thoroughly.”

The same goes for a couple choosing a mortgage or a car, Minson cautions. “Just because you make a decision with someone else and you feel good about it, don’t be so sure that you’ve solved the problem and you don’t need help from anybody else,” she said.

The findings appear in the journal Psychological Science.

Source: Association for Psychological Science 

Two Heads Not Always Better Than One

Janice Wood

Janice Wood is a long-time writer and editor who began working at a daily newspaper before graduating from college. She has worked at a variety of newspapers, magazines and websites, covering everything from aviation to finance to healthcare.

APA Reference
Wood, J. (2018). Two Heads Not Always Better Than One. Psych Central. Retrieved on November 24, 2020, from
Scientifically Reviewed
Last updated: 8 Aug 2018 (Originally: 8 Mar 2012)
Last reviewed: By a member of our scientific advisory board on 8 Aug 2018
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