The world is full of people who have excessive confidence in their own abilities. This is famously described as the Dunning-Kruger effect, which describes how people who lack expertise in something will necessarily lack the knowledge needed to recognize their own limits. Now, a different set of researchers has come out with what might be viewed as a corollary to Dunning-Kruger: People have a strong tendency to believe that they always have enough data to make an informed decision—regardless of what information they actually have.
The work, done by Hunter Gehlbach, Carly Robinson, and Angus Fletcher, is based on an experiment in which they intentionally gave people only partial, biased information, finding that people never seemed to consider they might only have a partial picture. "Because people assume they have adequate information, they enter judgment and decision-making processes with less humility and more confidence than they might if they were worrying whether they knew the whole story or not," they write. The good news? When given the full picture, most people are willing to change their opinions.
The basic setup of the experiment is very straightforward. The researchers developed a scenario where an ongoing water shortage was forcing a school district to consider closing one of its schools and merging its students into another existing school. They then wrote an article that described the situation and contained seven different pieces of information: three that favored merging, three that disfavored it, and one that was neutral. Just over half of the control group that read the full article favored merging the two schools.
