Ever wonder why girls are so fixated on swapping friendship bracelets? They may just be wired that way, according to a new study. Using MRIs to look inside tweens' and teens' brains, researchers found that one-on-one interactions got girls’ synapses firing, Time reports. Boys focused less on other individuals than they did on groups and competition—a possible evolutionary adaptation that helps prepare them to deal with rivals for females' affection.
Researchers hooked kids aged 8-17 up to an MRI and asked them questions about a series of pictures of people who, the kids believed, they’d eventually meet. The girls’ brains lit up as areas associated with reward and motivation, hormone secretion, and subjective feelings kicked into overdrive. No such activity registered for the boys. It’s possible, researchers say, that they just didn’t care about the pictured people.