The differences were linked to the mental alertness required to switch between languages, which could develop skills useful in other types of thinking.
He suggested that applicants to the police should be required to have certain languages, spoken in minority communities, or to have done voluntary work, rates of which are thought to be high in ethnic minority groups.
Virtually everyone who had graduated from a technical, medical or foreign-languages college was considered an officer of the reserves and required to report for regular training exercises.