You better knock off that awful attempt at a Scottish brogue, mate: A team of researchers has found that people in the northern United Kingdom and Ireland are especially good at telling when you’re faking it.

The research surveyed nearly 1,000 participants from across the UK and Ireland and found that individuals from Ireland, Northern Ireland, Scotland, and northeastern England were better at identifying mimicked native accents than participants from farther south. The team’s research is published today in Evolutionary Human Sciences. The new paper focused exclusively on people from the UK and Ireland, but it’s a fair warning for those of us in North America about attempting those awful accents.

“We found first that people across groups are better than average when detecting when someone is faking any accent (across the seven accents in the UK and Ireland we evaluated),” said Jonathan Goodman, a researcher at the University of Cambridge and corresponding author of the paper, in an email to Gizmodo.  “Second, we found that some groups of native speakers are better than others at detecting when someone is faking their own accent.”

The team recorded speakers using accents from northeast England, Belfast, Dublin, Bristol, Glasgow, Essex, and standard British English. The participants were asked to record themselves saying several test sentences, including “She kicked the goose hard with her foot,” “Jenny told him to face up to his weight,” “Kit strutted across the room,” “Hold up these two cooked tea bags,” and “He thought a bath would make him happy.” The sentences include words that are particular ‘tells’ for whether the speaker’s accent was authentic or spoofed.

“We worked with the phonetics lab here in Cambridge to develop sentences that teased out accent-specific phonemic differences in pronunciation of specific words,” Goodman said. “For example, for some people the word ‘bath’ rhymes with ‘path’; for others, with ‘moth.’ These differences make up what we can call accent-specific signals linked with regions across the UK and Ireland.”

The participants’ recordings were played in 2 to 3 second clips for other participants. The team found that participants from Belfast were the best at identifying fake accents, with locals in northeastern England and Dublin being second- and third-best. Listeners from Essex, Bristol, and London were the least accurate.

“This narrative both predicts better mimicry detection among speakers from places with high-between group tension, such as Belfast, Glasgow and Dublin, and explains why an area like Essex may also have relatively poor mimicry detection,” the team wrote in the paper. “Specifically, speakers of the Essex accent moved to this area over the past 25 years from London—a strong contrast with speakers living in Belfast, Glasgow and Dublin, whose accents evolved over centuries of cultural tension and violence.”

That’s one side of the coin. The other side, the team suggested in the paper, is that people in London and Bristol may be less attuned to specific accents because they are surrounded by a more diverse array of accents on the day-to-day.

The research brings to mind a baffling medical case described last year, in which a man suffering from metastatic prostate cancer developed “an uncontrollable ‘Irish brogue’ accent despite no Irish background,” according to research published in BMJ Case Reports. That team concluded the man suffered from foreign accent syndrome, a real thing that causes listeners to perceive changes in a person’s speech as an accent. That work did not indicate how convincing the Irish brogue was.

The recent study only surveyed participants from the UK and Ireland, but Americans—let’s not even pretend we do a decent British or Irish accent. I think we’d all be better off not trying.