Control group showed an average gain of 21 points. A follow-up study in 1966 showed this difference to be long lasting. So, it seems as if early experiences can have an effect. Proposition IV Deliberate attempts to increase the level of intelligence by special enrichment or experiences should have no effect. The evidence which disputes this proposition comes from three types of studies.
Deprivation studies eg.
For each of the above studies, read and make notes. Make sure you include details of the sample, method, results, conclusions and comments. It seems that psychological differences are inherited but that environment must also play a part. Perhaps it is as we said in the beginning, our genes determine what we could be capable of and our environment and experiences determine how much we achieve this. All of the above studies were based on small samples.