Communicative competence involves 'knowledge of when to speak or be silent: how to speak on each occasion: how to communicate (and interpret) meanings of respect, seriousness, humour, politeness or intimacy' (Milroy 1980: 85). Speakers also have to acquire an understanding of the social meaning of different linguistic varieties and different linguistic forms. For example, in a situation described by Gumperz (1982a), where a Black college student switched from standard American English to Black English in a college context, that switch had communicative significance: it was a comment to other Black students present that 'I'm just playing the game'. Another example is provided by Labov's Harlem study: as members of the (male) Black subculture, the adolescents studied by Labov are able to recognise the utterance Your mother wears high-heeled sneakers to church as a ritual insult, more particularly, as the opening move in a 'sound' (since opening moves normally refer to the addressee's mother).