From Anna's language acquisition thread that Faldage brought back up:
There, Sparteye brings up one Dr Tsunoda's research on the brain. He's quoted as saying, "I believe that the mother tongue differenciates the way in which people receive, process, feel, and understand sounds in the external environment.... The mother tongue is closely related to the development of the emotional mechanism in the brain. I conjecture that the mother tongue acquired in childhood is closely linked with the formation of the unique culture and mentality of each ethnic group."