A difference between boys and girls

On a few occasions in the car lately, Wes and I have been discussing a difference between girls and boys that he has noticed.  Evidently, girls love to draw hearts and boys not so much.  I told him that I thought that the only real difference between girls and boys was that boys had penises (trying to not be shy of using the correct vocabulary), but duly noted, the other difference that I had not known previously, is that one group loves to draw hearts.  Then I said that I didn't really think it was a true difference, but maybe it showed that boys were not very brave because they were just afraid what other boys would say if they were to draw hearts.  "No, no, no - I only draw hearts to show I love someone.  I just don't like the shape. Boys just don't like the shape of the heart."  I wondered then to him whether girls draw hearts more because they just love more, love people, love life, etc.  "No, no, no, it's just the shape." Good observation - but what is the real answer?