Braggarts like Donald Trump might like to openly shout out their achievements because they are simply not clever enough to do it in a more subtle way, new research suggests.
Hardly a week goes by without the US President boasting about one thing or another, whether it's having "one of the highest" IQ scores in the world, the "best words" or being the best guest the Queen has ever hosted.
But for some reason, braggadocio like this turns people off.
"Standard theories used by biologists and economists to model human behaviour predict that people will be strongly motivated to make their positive traits and admirable acts known to others," said Tadeg Quillien, a graduate cognitive science student at the University of California, Santa Barbara.
"Yet in real-life people avoid bragging openly about their achievements."
To find out why this is Quillien developed a complex game, which found clever people are able to send 'buried' signals which convey their quality.
"The act of deliberately making a signal hard to note is itself a signal: it conveys the message that you are confident that people will find out anyway, or that you do not really care about reaching out to those who would miss the hidden message," Quillien wrote in the study.
In contrast, for example he notes people react badly when someone constantly mentions they have a college degree.
"Plain bragging about his education would give away the fact that he is not smart enough to advertise his mental agility indirectly."
Quillien gave a number of examples where people deliberately bury signals in order to quietly impress others they deem worthy.
"Philanthropists often make massive donations under cover of anonymity, and observers consider such anonymous giving more virtuous. Artists hide some of the meaning of their work as easter eggs for spectators to discover, novelists publish some of their books under pseudonyms and fashionistas sometimes buy expensive designer clothes that do not feature the brand logo."
Most people who aren't clever enough to get the message across in a subtle way also stay quiet, as bragging would reveal their lack of quality, Quillien says.
But as the US President demonstrates, that doesn't hold true for all. Quillien turns to toads to explain why this is.
"The pitch of a toad's croak is a good indicator of its size, so toads vocalise in order to intimidate their rivals - but surprisingly even small toads vocalise, giving away their small size.
"This is because not vocalising at all is the worst signal a toad could send about his formidability: it would be an implicit confession that the animal has strictly nothing good to show... even individuals who are not adept at demonstrating their positive attributes in a subtle manner may find themselves inclined to do so."
The research was published in journal Proceedings of the Royal Society B.