 A survey carried out in the 1960s studied people’s attitudes towards usage problems in English.The examples "you'd better go slow" (rather than "slowly") and "he did it quicker than he'd ever done it before" (rather than "more quickly") contained flat adverbs – and the latter was found to be acceptable by just 42% of respondents.However, in a follow-up by the Leiden University Centre for Linguistics, using the same examples from the 1960s survey and others containing flat adverbs, they found that acceptance of flat adverbs has become much more widespread in recent years.