The cognitive tradeoff hypothesis argues that in the cognitive evolution of humans, there was an evolutionary tradeoff between short-term working memory and complex language skills. Specifically, early hominids sacrificed the robust working memory seen in chimpanzees for more complex representations and hierarchical organization used in language. The theory was first brought forth by Japanese primatologist Tetsuro Matsuzawa, a former director of the Primate Research Institute of Kyoto University (KUPRI).
Matsuzawa suggests that at a certain point in evolution, because of limitations in brain capacity, the human brain may have acquired new functions in parallel with losing others – such as acquiring language while losing visuospatial temporal storage ability.