Have you ever heard a word in a foreign language and thought it sounded profane or rude for some inexplicable reason?

Well, a new series of studies suggests you might be onto something.

Psychologists from the University of London have found a characteristic of words we use to swear that's consistent across a variety of languages, and it might represent a universal phonetic pattern.

According to the psychologists Shiri Lev-Ari and Ryan McKay, swear words around the world typically lack 'approximants' – sounds made by bringing our lips, teeth, hard palate or tongue close to one another without quite making contact. Think of the y sound in 'yes', the r sound in 'run', or the w sound in 'war'.

Consonants in words containing approximants are less likely to drown out their neighboring vowels, creating a softer sound when spoken than those that use 'plosive' letters like p, t and k, which make words like 'pop' or 'kart' sound blunt.

The near universal lack of approximants in swear words helps makes them sound harsh, regardless of the language. The findings suggest swear words might have been sculpted by a shared bias in the human brain.

Sound symbolism is the idea that some phonetics trigger a universal cognitive response that helps make the perception of certain sounds consistent across different languages.

For instance, studies have shown that the speakers of more than 20 different languages all tend to associate the nonsense word 'bouba' with a round shape and 'kiki' with a sharp one.

These findings suggest some consonants might sound more cutting to human ears than others, and that could apply to swear words too.

To test that idea, researchers asked 20 fluent speakers of five distant languages to name as many swear words as they could.

After removing repetitions, variations, and racial slurs, researchers settled on 34 swear words and phrases in Hebrew, 14 in Hindi, 14 in Hungarian, 17 in Korean, and 26 in Russian.

Analyzing the sounds of these words, researchers found no indication that swear words contained more plosives than usual. But they did notice a clear absence of approximants in swear words, including the sounds of l, r, w, and y.

The authors created two experiments to see how these sounds are perceived.

The first study tested whether 215 participants who spoke six different languages were able to guess if a pseudo swear word was offensive based on how it sounded.

Ultimately, those words that contained approximants were less likely to be considered swear words than those words that contained no hint of l, r, w, or y sounds.

French appears to have relatively more swear words with approximants than other languages, but even among French speakers, researchers found words lacking approximants were still selected as swear words 63 percent of the time.

A final follow-up experiment tested the dulling effect of approximants on euphemistic swear words like 'darn' (instead of 'damn').

The authors call these words 'minced oaths', and approximants are a common feature.

Compiling a list of 24 minced oaths that are altered versions of swear words, researchers found more evidence that l, r, w, and y sounds convey restraint.

The authors describe approximants as the verbal equivalents of compressed air hinges on doors. Even if you throw your words in anger, the sound of an approximant can muffle the perceived effect.

But this idea is probabilistic, the authors clarify, not deterministic.

Recent studies, for instance, have found that the sound of 'i' tends to be tied to small-sized objects in a variety of distant languages, but that doesn't mean every human language has settled on a word like 'bambini'.

"What our results point to is an underlying cognitive bias, a predisposition that will have acted in concert with historical accident to shape the evolution of swear words," Lev-Ari and McKay write.

"Just as the association between nasal sounds and words for "nose" does not manifest in every language – or even in most languages – we should not expect that the pattern we have identified will manifest in every language, and even languages that reflect the pattern are likely to have swear words with approximants, though fewer than would be predicted by their sound system."

If the authors are right, sound symbolism might be more pervasive in our languages than many suspected. It goes far beyond object size or shape. Sounds might change how listeners perceive a speaker's attitude, emotion, or arousal.

Linguists have been arguing for decades over whether human language is culturally acquired or a feature of our brain biology. Like most nature-nurture debates, the answer is likely to be more complicated than the question.

More evidence for the universal nature of sound symbolism is needed, but at least at the practical level, the authors say their findings could be used to help diffuse tense social situations.

Might be worth a try this holiday season.

The study was published in the Psychonomic Bulletin & Review.