The groundwork for the pay gap so many women workers confront at work may actually be set in motion while they are still in elementary school, recent research at Boston College’s Cooperation Lab suggests. By around age 8, kids start to display behaviors socially-reinforced for their gender, including the negotiation skills they will need as they discuss salary requirements with their superiors.

For the study, the first of its kind to identify a gender-driven “negotiation gap” in children so young, 240 children, aged 4-9, were asked to negotiate with male and female evaluators. They were told to complete a task, then were allowed to ask for as many stickers as they wanted as a reward. Evaluators were instructed to push back on requests for more than two stickers.

Between the ages of 4 and 7, the children in the study displayed equal ability to negotiate regardless of gender. By the age of 8, however, girls in the study were observed requesting less than boys when negotiating with a man.

Girls and boys negotiated just as much as one another, with one exception. When girls had to negotiate with a man, they asked for fewer stickers than when attempting to negotiate with a woman.

“We found that — consistent with adult work — girls asked for less than boys when negotiating with a man. We did not see this gender gap when children were negotiating with a woman,” lead autho,r Katherine McAuliffe, said in a statement.

Girls requested fewer stickers the older they got when asking from a man, and requested more stickers with age if the evaluator was a woman. Boys’ requests remained consistent regardless of the evaluator’s gender. The findings bear a striking similarity to similar studies done with adults, the study’s authors say.

Between the ages of 4 and 7, the children in the study displayed equal ability to negotiate regardless of gender. By the age of 8, however, girls in the study were observed requesting less than boys when negotiating with a man.

Given that managerial and executive positions in the workforce skew heavily male, this may spell difficulty down the line for girls negotiating their first salaries and work responsibilities, as well as their general ability to advocate for themselves with the men in their lives.

Similar trends have been seen in the context of school. Studies have found that boys and men tend to over-evaluate their competency in science, while girls underestimate theirs. In kindergarten, boys and girls do equally well in math, but by the second grade (about the same age when the negotiation gap emerges), research has shown that girls’ confidence in their number skills, as well as their math performance, starts to decline.

“Learning when these gender differences emerge is imperative for understanding what individual and societal factors lead to these gender differences in adulthood,” McAuliffe and study co-author, NYU graduate student Sophie Arnold, write.

More studies are needed determine what role cultural factors may play in the gendered negotiation gap, and whether intervention strategies can be taken early on to bolster girls’ negotiation skills. In the meantime, “one thing this tells us is that we should be teaching young girls to advocate for themselves in the context of negotiation from as early as elementary school,” McAuliffe said.

The study is published in Psychological Science.