Being at the top end of the income scale doesn't necessarily mean you're all that smarter than the average person, according to a new study – and those in the top 1 percent of the earnings scale score lower in cognitive ability tests than those earning slightly less than them.

Researchers of the study argue that this "plateauing of cognitive ability" amongst the biggest earners shows that at the very top pay scales, the resources available due to someone's family background and lucky breaks in careers carry more weight than overall intelligence.

A team of researchers from Linköping University in Sweden, the European University Institute in Italy, and the University of Amsterdam in the Netherlands say that better cognitive ability plays more of a role further down the pay scale.

"We find that the relationship between ability and wage is strong overall, yet above €60,000 (US$64,407) per year ability plateaus at a modest level of +1 standard deviation," write the researchers in their published paper.

"The top 1 percent even score slightly worse on cognitive ability than those in the income strata right below them."

This is based on data from 59,387 Swedish men who completed a military conscription test aged 18 or 19. While this limits the findings in terms of nationality and gender, it still provides a relatively large sample across a variety of pay levels and occupations.

The findings challenge the standard narrative that many live in a meritocracy where success and higher levels of income are earned by superior intellect and talent. In the most successful, the data here show intelligence does not increase as much as success when going further and further up in earnings.

That's not to say that being clever or studying hard doesn't matter at all in terms of how much you earn – it does play a part – but that at the top pay levels, other factors come into play, and those factors take on more significance over time.

These can include things such as socioeconomic background, culture, personality traits, and luck.

"Small initial success differences between individuals are not canceled out over time but instead grow into winner-take-all distributions characterized by extreme inequalities," write the researchers.

The study also found that with higher pay scales, job prestige doesn't increase with cognitive ability: In professions such as doctors, lawyers, and professors, more prestige doesn't seem directly related to more income.

All of this is important in a world where the ultra-rich continue to get richer and have more influence over global political, social, and economic landscapes. These very top earners aren't always going to be the smartest people in the room.

With increased focus on inequality across the world, the argument that those taking home the most pay deserve it the most is one that needs to be challenged, the researchers point out – especially at the highest end of the scale.

"Recent years have seen much academic and public discussion of rising inequality," write the researchers. "Along an important dimension of merit – cognitive ability – we find no evidence that those with top jobs that pay extraordinary wages are more deserving than those who earn only half those wages."

The research has been published in the European Sociological Review.