Background to my interest in teaching children with autism

PSYCHOTHERAPY BEYOND THE FRINGE, continued
Like all scientists, including psychologists, Felicity learned this sort of nonsense at school. Like you, he knew it had to be tommy rot. So he had to keep ‘reinventing this wheel’ all through his career. He thought psychiatric conferences, which tried to bring together everything that could be known about a patient, must be the way to reach good and reliable evaluations of patients. It took quite a long time, and a lot of reliance in his research work on this unreliable source of information, before he had disabused himself of that idea.
He was working on some research with the Rorschach inkblot test. He found about 120 heterogeneous (‘uncorrelated’) variables all of which, individually, significantly but imperfectly predicted something he wanted to measure. He combined all of them into a single scale, and it lost all predictive significance. After much fiddling around, it ended up that combining any 5 to 7 of these variables in a scale produced the best level of prediction, better than combining any fewer or any more variables.
In the same research, he found 32 homogeneous (‘correlated’) variables all of which, individually, significantly but imperfectly predicted something else he wanted to measure. When he combined all 32 in a scale, he lost all significance in his prediction – it did not predict at all. After much fiddling, it ended up that any 16 of these variables combined in a scale produced the best level of prediction, better than combining any fewer or any more.
Later in his career, having forgotten this experience, he tried combining a group of 50 and a group of 100 questionnaire items all of which significantly predicted what he was trying to measure. He had no predictive efficiency at all. The 50 items were uncorrelated (heterogeneous), and it turned out the best predictive efficiency was obtained using any 7 of the items. The 100 items were inter-correlated (homogeneous), and it turned out the best predictive efficiency was achieved using any 16 of them.

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