Little Man Syndrome in Horses?

We all make jokes about people that are, umm, vertically challenged let's say. They have tempers or this and that, but is it possible in horses? You all have seen Chance is our newest addition, and he is vertically challenged. Very muc so... Then you know that Nehi is our biggest by far. So how is it that Chance bully's Nehi. Severely to the point Nehi was hiding behind Fritz.. Kind of like really tall people are normally pretty relaxed, that sums Nehi up. So back to the question, can horses have little man syndrome, or do they think they are really big kind of like small dogs? Come by sometime and see my little man (just don't call him that!)