To uncover what defines an act as “stupid,” the researchers analyzed real-life examples of stupidity. They first built a formidable assortment of 180 stories describing stupid actions collected via the Internet and from daily reports provided by a group of 26 college students. All of the stories were reviewed by a group of seven raters to ensure that they described a “stupid” action, were comprehensible, and were relatively brief.

The next phase of the study called for a large group of participants to assess the stupidity of each story on a 1-10 scale, determine from a list of thirty psychological factors what precisely contributed to the stupidity, rate the responsibility of the actor and environment in the situation, and gauge any associated consequences. 154 undergraduates (122 females) took part, completing one of twelve questionnaires each containing fifteen stories from the large pool.

Importantly the undergraduate subjects showed wide agreement on what was stupid and what wasn’t, hinting at a common definition.