Less than 10 Your mother would be proud. Your swearing ability is below average (or at least you came up with fewer swear words than the average participant in a recent American study – perhaps we Brits have a more colourful vocabulary in general).
More than 10 Congratulations! You know more swear words than the average American!
Why congratulations? Well, contrary to popular belief, knowing a lot of swear words is not a sign of a limited vocabulary. In fact the opposite is true. A 2015 study found that people who were good at coming up with swear words were also good at coming up with animal names and with words that begin with a particular letter.
This study also found correlations between swearing vocabulary and personality. People who knew a lot of swear words tend to be open to new experiences, but also more neurotic, less agreeable (ie harder to get along with) and less conscientious (ie more likely to adopt a “will this do?” approach). Note, however, that the study looked at how many swear words people knew, not how often they used them in everyday conversation. So while knowing lots of swear words is a good thing, your mum was right in that swearing itself is not (necessarily) big or clever.