http://media.caltech.edu/press_releases/13492

To investigate the impact of social context on IQ, the researchers divided a pool of 70 subjects into groups of five and gave each individual a computer-based IQ test. After each question, an on-screen ranking showed the subjects how well they were performing relative to others in their group and how well one other person in the group was faring. All of the subjects had previously taken a paper-and-pencil IQ test, and were matched with the rest of the group so that they would each be expected to perform similarly on an IQ test.

At the outset, all of the subjects did worse than expected on this "ranked group IQ task." But some of the subjects, dubbed High Performers, were able to improve over the course of the test while others, called Low Performers, continued to perform below their expected level. By the end of the computer-based test, the scores of the Low Performers dropped an average of 17.4 points compared to their performance on the paper-and-pencil test.

"What we found was that sensitivity to the social feedback of the rankings profoundly altered some people's ability to express their cognitive capacity," Quartz says. "So we get this really quite dramatic downward spiraling of one group purely because of their sensitivity to this social feedback." Since so much of our learning—from the classroom to the work team—is socially situated, this study suggests that individual differences in social sensitivity may play an important role in shaping human intelligence over time.