The wisdom of (smaller) crowds

When guessing the weight of an ox or estimating how many marbles fill a jar, the many have been shown to be smarter than the few. These collective displays of intelligence have been dubbed 'the wisdom of crowds,' but exactly how many people make a crowd wise?

New research by SFI Professor Mirta Galesic and her colleagues from the Max Planck Institute for Human Development in Berlin suggests that larger crowds do not always produce wiser decisions. In fact, when it comes to qualitative decisions such as "Which candidate will win the election" or "which diagnosis fits the patient's symptoms," moderately-sized 'crowds,' around five to seven members, are likely to outperform larger ones. In the real world, these moderately-sized crowds manifest as physician teams making medical diagnoses; top bank officials forecasting unemployment, economic growth, or inflation; and panels of election forecasters predicting political wins.

"When we ask 'how many people should we have in this group?' the impulse might be to create as big a group as possible because everyone's heard of the wisdom of crowds," Galesic says But in many real world situations, it's actually better to have a group of moderate size."

Where previous research on collective intelligence deals mainly with decisions of 'how much' or 'how many,' the current study applies to 'this or that' decisions under a majority vote. The researchers mathematically modeled group accuracy under different group sizes and combinations of task difficulties. They found that in situations similar to a real world expert panel, where group members encounter a combination of mostly easy tasks peppered with more difficult ones, small groups proved more accurate than larger ones.

"In the real world we often don't know whether a group will always encounter only easy or only difficult tasks," Galesic says. "And in many real world situations, an expert group will encounter a combination of mostly (for them) easy tasks and a few difficult tasks. In these circumstances, moderately-sized crowds will perform better than larger groups or individuals. Organizations might take this research to heart when designing groups to solve a series of problems."