It is definitely partly an age related thing. All babies go through a chewing stage, it helps them feel secure chewing on something, its also their way of seeing what things are, and showing that they are submissive to the leader. It is your choice to correct it or not. I chose not to with my mare because it was truly a stress related issue, and getting after her just increased her stress, but ignoring her, and letting her settle in, and get used to all the people she now sees and all the activity, its gone away on its own, that being said, if she starts to get grabby which she has, I do get after her about that, because grabby for the rope, or whatever she's going after down the road turns into grabby for treats, or grabby persons arm or leg or head for attention, and that is unacceptable. She knows her boundaries, and what is acceptable and what is not, and that is my ultimate goal with her, is her being respectful. My reprimand is a swift tap to the shoulder or neck, as I'm removing the lead rope from her mouth, as she does not need any more than that, and I refuse to do any sort of tapping smacking pushing ect. to her head.