Yea, humans are not cats, just because your head fits, does not mean your body fits. Unless you can easily get your head between a gate, don't play that game. The only way you're getting between a gate is if you can slide through sideways. Humans have far broader shoulders and far more rigid skeletons than most animals. Try messing around with your shoulders and torso in front of a mirror, you'll realize just how much bigger they are than your head, the latter of which most people can do basically nothing to alter the size of. The only other similar animals off the top of my head are like chimpanzees and gorillas; IE bipedals sharing common ancestry. Even that isn't absolute considering the structure of some smaller monkeys out there. That head rule typically only applies to quadrupeds. Most commonly felines and rodents.