As she conceded the US election to Donald Trump in November, one part of Hillary Clinton’s speech stood out.

“To all the little girls watching this,” she said, “never doubt that you are powerful and valuable and deserving of every chance and opportunity in the world to pursue and achieve your own dreams.”

Now, a major new study suggests that Clinton’s message wasn’t just poignant – it was vital.

Researchers in the US have found that primary school-age girls lack belief in their own abilities when compared to their male peers. Girls as young as six are convinced that boys are more innately brilliant or gifted than them, the Guardian reports.

The research, published in the journal Science, also showed that girls – unlike boys – are more likely to put good grades down to hard work, rather than natural talent.

Psychologists from three American universities carried out a range of tests with 400 girls and boys aged between five and seven to examine how gender stereotypes affected children’s beliefs about intelligence and ability.

Tests included matching traits (such as “being smart”) to pictures of men and women, and guessing the gender of a “highly intelligent” character in a story.

Read more: Meet the 11-year-old feminist bloggers fighting for equality online

It was discovered that five-year-old girls are just as likely as boys to associate brilliance with their own gender. Once girls reach six or seven, however, they are far less likely to believe in female intelligence.

Six-year-old boys identified people of their own gender as being “really, really smart” 65% of the time. For girls of the same age, that figure shrank to 48%.

Researchers next investigated whether children expected boys or girls to do better at school. Counterintuitively, while girls aged five to seven were more likely to think their own gender would get good grades, they didn’t attribute this academic success to their own intelligence. They were also more likely to want to play a game that required them to “try really, really hard” than to be “really, really smart”.

Read more: This is how stress affects boys and girls differently

Andrei Cimpian, a psychology professor at New York University and one of the co-authors on the study, said that the results reveal the extent to which girls’ self-belief is hampered by gender stereotypes.

“Already by this very young age girls are discounting the evidence that is in front of their eyes [academic success] and basing their ideas about who is really, really, smart on other things,” he said.

“Because these ideas are present at such an early age, they have so much time to affect the educational trajectories of boys and girls.”

Christina Spears Brown, a professor of psychology at Kentucky University, said that the new study fits in with previous research that suggests parents and teachers put girls’ good grades in maths down to hard work, while believing that high-achieving boys were simply naturally gifted.

“This study shows that girls are internalizing those cultural messages early in development, believing that, yes they may work hard, but they are not naturally really smart,” she said.

“These beliefs can have important implications for what types of academic paths children choose to take, and shows why girls are opting out of majors like physics, despite earning high grades in school.”

So next time you’re hanging out with your little niece/daughter/sister/cousin/friend’s kid, make sure you channel Hillary Clinton and remind her of what she has to offer. In all likelihood, it will be something she needs to hear.

Images: iStock