Examines whether instructing Nigerian primary children in science in their mother tongue (Yoruba) is any more efficacious than instructing them in science in the English language. Also assesses and compares the levels of cognitive development of two groups of Yoruba-speaking children, one instructed in Yoruba and another in English. (CS)

Initial textbook investigations indicate that more new words/phrases are introduced than in a similar time frame in which foreign languages are studied. Reviews these initial studies, studies of vocabulary mastery in foreign languages, and general research concerning vocabulary development. Reports on occurrence of technical/special words in 25…