My ds (11 months) has recently started headbutting. He tries it on many things, walls, toys and people. DH thinks its cute when they headbutt each other and takes it as a sign of affection?! so half encourages it. Only problem is my DS is a big baby (is already in 18-24 month clothes) and a lot bigger than most children his age. My cousin was visiting with her baby (18 months) who is quite tiny, and heads smaller than my DS. Anyway put them in playpen to play and he started headbutting her, leading to tears from cousin's baby! Apologised to cousin and separated them. Told my DS he should not do this but TBH at his age dont really think he understands it's not accepted, and especially since DH kind of half encourages it! Is this just a phase he will grow out of? My other DS (11 years) didn't do anything like this!