This is a pretty charged topic, and it's difficult to make the case unequivocally. In our family, it got to the point where people were emailing research papers(academics and doctors in the family) back and forth and Christmas was ruined. I don't have time to cite all the papers on both sides of this, but for us(my wife feels even more strongly about this than I do), it came down to the realization that AT BEST all the girl's toys and clothes could do no harm to their psyche. AT WORST, it could possibly instill in them a type of inferiority with respect to boys in terms of technical ability, and a diminished sense of their place in the world with respect to boys. As a scientist, I have to consider all the evidence, and as a parent, I have to make the decisions I think will help make my children stronger. My wife and I basically came to the conclusion that "girl's toys" and "girl's clothes" were bullshit, and an unnecessary risk to their psyche. Unfortunately pink is collateral damage in this war, as it is so ubiquitously used in our culture to demarcate girl from boy. I can in no way say that we are right, not in a scientific sense, I can only say that after spending hours and hours in toy and clothes aisles, I would say as a culture it's time to rethink gender neutrality, and the way we are separating boys and girls with clothes and toys from a very young age.