Look at the psychology of boys taking pictures

Putting your hands in front of you and holding them down is a typical self-defense mentality. Your hands form a line of defense to block the intrusion of photographers and other people. Taking such a pose when taking a photo with a girl is a sign of rejection. Putting his hands behind his head and opening his chest is a welcoming attitude. This posture shows that his heart is happy and satisfied at that time. This is when he is most relaxed and happy.