When children are very young, they often find it incredibly easy to make lots of friends to play with.
Children bond over the simplest, most insignificant of things and pay very little attention to whether their new pal is the same gender as them or not.
And according to Vanessa LoBue, an assistant professor of Psychology at Rutgers University in New Jersey, that's because toddlers don't really know all that much about gender stereotypes until they start to get a little older.
Speaking to smartparenting.com.ph, Vanessa explained: "In my own research, I've found that children don't begin to notice and adopt gender-stereotyped behaviours (eg. preferring colours like pink or blue) until the age of two or three."
These gender stereotypes, once learned, can hinder the growth of friendship between boys and girls as they begin to notice differences between themselves and become conscious of it.
As well as this, one of the main things that can hinder a friendship between a young boy and girl is the early pressure that parents put on the relationship, by referring to their child's friend as their "boyfriend" or "girlfriend".
Teasing your child about this, when they don't fully understand what the terms mean, can cause them to feel embarrassed and shy away from the blossoming friendship.
In a recent article, parenthood advice columnist Elissa Strauss argued that it might be better to simply encourage friendship between boys and girls, without putting labels on it.
She wrote: "Girl-boy friendships can help undo some of these socialized gender constraints.
"When parents approve of these relationships, they are sending their children the message that it's not only ok to play with another gender, but it is also ok to play like them. Children learn fast."
And there are various other benefits that can come out of boy-girl friendships.
These include, learning off each other's strengths, learning different ways of resolving conflict and improving romantic relationships in later life.
This is because traditionally girls like to talk more than boys, who prefer focusing on the rules as opposed to their emotions - but playing with girls could encourage them to open up more.
Psychologist Michael C. Reichert added: "If boys are able to retain close relationships with girls and negotiate friendships with girls [while young], then they come to romantic relationships much better prepared for intimacy, rather than just sexual gratification."
Are you the black sheep of your family?