In fact, these "special" children were randomly selected and no smarter than their classmates. At the end of the term, all the students were tested, and the results made an important point. The "special" children not only performed better in the eyes of their teachers (an expected outcome, the so-called "halo effect"), but they also scored significantly higher on standardized IQ tests.
In other words, teachers' expectations had improved the academic performance of their students. Where they expected success, they found it. Later, Rosenthal conducted additional experiments, among them a study with laboratory mice where rodents labeled as "maze-bright" (bred to successfully navigate mazes but, in reality, no different than normal mice) actually performed better in maze tests. On further study, Rosenthal's team found that the laboratory researchers handled the "maze-bright" mice more often and more gently than the others.