Free and not-so-free variation

As we saw, [t], [th] and [?] are all allophones of /t/. There is, however, an important difference here between the distribution of [t] and [th] on the one hand, which are in complementary distribution and cannot occur in the same environments, and [?] on the other, which appears (at least in some environments) to substitute freely for [t], as in the water example above: many speakers in fact switch between the two. Similarly, in Spanish, which does not have a phonemic opposition between /b/ and /v/, the word Vale! (‘Ok!’) can be pronounced [bale], [vale] or  is the IPA symbol for a voiced bilabial fricative), and be understood in the same way in each case. Alternation of this kind, which is unconstrained by phonetic environment, is known as free variation and was long dismissed by linguists as being of little theoretical interest – a case of ‘You say tomayto, and I say tomahto’, if you like – and scarcely worthy of comment (‘…so let’s call the whole thing off’). There is, however, a very important difference between water as  and as , namely that the latter pronunciation, in British English at least, is of considerably lower status than the former, something of which most speakers are acutely aware. The variation, then, is socially rather than phonetically conditioned.

Linguists long chose to ignore this obvious fact on the grounds that social data should not be allowed to intrude upon linguistics if it were to establish itself as an autonomous discipline and be taken seriously as a science. This consensus was challenged in the 1960s by sociolinguists who argued that no satisfactory explanation of language change could be provided without taking account of social factors. As we shall see, their findings have forced us to revise our view of how ‘free’ so-called free variation actually is.