Georgia Tech scientists test college freshmen by giving them increasingly longer segments of the SAT test. Interestingly, as the length of the test increased, so did the students’ scores:
The average score on the three-and-a-half hour test was 1,209 out of 1,600. On the four-and-a-half-hour version it was 1,222; on the five-and-a-half-hour test it was 1,237. Virtually all of the students followed that pattern.
The theory is that competitive students have learned to use stress and exhaustion to create concentration. Scientists refer to this phenomenon as achievement motivation.