http://www.eugenics.net/papers/eb2.html
Over the past three decades, hundreds of experiments, many carried out on a massive scale, have sought to prove that intelligence can be substantially raised. In a few studies, subjects were given intensive training over a period of several years. No other field of psychological or educational research has commanded such vast funds nor marshalled such concerted efforts on such a grand scale. The truly remarkable finding is not the few points gain in IQ or scholastic achievement occasionally reported, but the fact that gains are so seldom found, and, when they are found, that they are so very small. The theoretical implication of this finding is that the behaviorist view of intelligence as synonymous with learning (or the products of learning) is seriously in error. Predictions based on this view have repeatedly failed to materialize under the prescribed conditions.
When gains in test performance have occurred as a result of educational treatments, they have displayed one or more of the following characteristics: (1) they have been small, rarely more than five or ten IQ points; (2) they have been of short duration, fading out within a year or so after the training has been completed; (3) they have been restricted to tasks or tests which closely resemble the actual training procedures themselves, and have failed to generalize to a broader range of mental tests.
...
It is now generally accepted that individual differences in IQ and information-processing capacity are strongly influences by hereditary factors, with genetic variance constituting about 70% of the total population variance in IQ (Jensen, 1981). There is also evidence that the genes for superior intelligence tend to be dominant, which is what would be theoretically expected if intelligence is a fitness character in the Darwinian sense, and if it had been subject to natural selection through the course of human evolution (Jensen, 1983).
Bookmarks