So in producing ‘mistakes’ like ringed instead of rang, and drinked instead of drank, Barbara has constructed new bits of English. They are perfectly understandable to the people she interacts with, but they don’t coincide with the forms these people use. In time, Barbara will attend to this discrepancy between her output and the input she receives, and will start to add exceptions to her rule.

The ‘add –ed’ rule she has worked out is a regularity of the speech of her community, but because of her overgeneralisation of it, her individual grammar isn’t identical to the community grammar for all past tenses.

Barbara revises her overgeneralised forms not because she can’t effectively make and share meaning with adult members of the community she’s being socialised into, but because we all, though not necessarily consciously, want to sound like the people we identify with. So, she revises her grammar for reasons of social identity rather than for communicative function.

In this sense, then, grammar rules are social markers: part of the customs and behaviours that identify a specific group of people, just as much as clothing, hairstyles, and body adornment (Fig. 3.7).

Notice, then, how easy it is to turn social regularities into regulations: just as certain cultural groups (e.g. religions, professions or gangs) might prescribe certain ‘rules of appearance’, so too linguistic ‘authorities’ tend to prescribe certain ‘rules of grammar’.