When people can learn what others think, the wisdom of crowds may veer towards ignorance.

In a new study of crowd wisdom — the statistical phenomenon by which individual biases cancel each other out, distilling hundreds or thousands of individual guesses into uncannily accurate average answers — researchers told test participants about their peers’ guesses. As a result, their group insight went awry.

“Although groups are initially ‘wise,’ knowledge about estimates of others narrows the diversity of opinions to such an extent that it undermines” collective wisdom, wrote researchers led by mathematician Jan Lorenz and sociologist Heiko Rahut of Switzerland’s ETH Zurich, in Proceedings of the National Academy of Sciences on May 16. “Even mild social influence can undermine the wisdom of crowd effect.”