James Harbaugh

“Rosenthal went on to study precisely that – what expectation mean for our children. In one line of research he showed that teachers´ expectations greatly affect their students´ academic performance, even when the teachers try to treat them impartially. For example, he and a colleague asked schoolkids in eighteen classrooms to complete an IQ test. The teachers, but not students, were given results. The researchers told the teachers that the test would indicate which children had unusually high intellectual potential. What the teachers didn’t know was that the kids named as gifted did not really score higher than average on the IQ test – they actually had average scores. Shortly afterwards, the teachers rated those not labeled gifted as less curious and less interested than the gifted students – and the students´ subsequent grades reflected that.
But what is really shocking – and sobering – is the result of another IQ test, given eight months later. When you administer IQ test a second time, you expect that each child´s score will vary some. In general, about half of the children´s scores should go up and half down, as a result of changes in the individual’s intellectual development in relation to his peers or simply random variations. When Rosenthal administered the second test, he indeed found that about half the kids labeled “normal” showed a gain in IQ. But among those who´d been singled out as brilliant, he obtained a different result; about 80 % had an increase of at least 10 points. What´s more, about 20 % of the “gifted” group gained 30 or more IQ points, while only 5 % of the other children gained that many. Labeling children as gifted had proved to be a powerful self-fulfilling prophecy.”
― Leonard Mlodinow, Subliminal: How Your Unconscious Mind Rules Your Behavior