As part of a study, a group of researchers from Harvard contacted an elementary school teacher at the beginning of a school year. They told the teacher that they had designed a test that would correctly predict which students were going to grow intellectually during the coming school year. (Someone called it "The Harvard Test of Intellectual Spurts" because he said it told which students were going to 'spurt' that year). The researchers promised it would indicate the right students. The test was said to be very, very accurate.

The researchers then administered, unbeknownst to the teacher, an obsolete IQ test. When the students had finished, the researchers threw the tests away. Then they picked five names at random from the roll book and told the teacher, "These are the students who are go…