Is this true, I mean, crystallizing intelligence?
But I read it (in school) that ones intelligence depends upon the size of the cortex respectively the number of its convolutions.
Or am I taking the whole thing wrong, please help :(

Hi Pooja, thanks for your comment.

An answer to your question can be found in one of the references cited in the article [ Improving fluid intelligence with training on working memory — Jaeggi et al., 10.1073/pnas.0801268105 — Proceedings of the National Academy of Sciences ]

” ... there is a long history of research into cognitive training showing that, although performance on trained tasks can increase dramatically, transfer of this learning to other tasks remains poor. Here, we present evidence for transfer from training on a demanding working memory task to measures of Gf. This transfer results even though the trained task is entirely different from the intelligence test itself. Furthermore, we demonstrate that the extent of gain in intelligence critically depends on the amount of training: the more training, the more improvement in Gf. That is, the training effect is dosage-dependent. Thus, in contrast to many previous studies, we conclude that it is possible to improve Gf without practicing the testing tasks themselves, opening a wide range of applications.”