One concern is that people who are aware that their speech is being recorded change their speech behaviour. Another concern is that speech behaviour is strongly influenced by the social situation in which the speaker performs. Speech produced in a court room, for instance, tends to be more formal in terms of vocabulary, syntax and phonetics than speech produced in one's living room. Also, read speech , especially when the linguistic material consists of isolated words , invokes a more formal and standard pronunciation than free conversation [Labov (1972)].