I've been trying to break down what makes up what we call "a good chin" and after analyzing several scientific studies and articles I am still, for the most part, stumped. First and foremost, "chin" is certainly a multi-factorial makeup. I don't think it's as simple as saying "alertness" * Anatomy: Size does play a significant role in your ability to take a shot. Of course, we have plenty of heavyweights who drop quite easily, but if you paired them against a Welterweight we would see a significant difference. Because concussions are usually caused by movement inside the skull, I don't believe that the thickness of a person's head contributes greatly to it, however a strong mandible and strong neck muscles probably play a role in reducing the whiplash caused by certain strikes. This whiplash targets a weaker part of the skull which increases the movement of the brain inside the skull. Furthermore, it seems some athletes simply have more durable brains. As in the brain requires a larger amount of force to shut down inside the skull. * Long term health: Because the brain is an organ that does not recover, its usually the case that anyone who has been dropped will likely be dropped again in the future. This is why as fighters gain experience and suffer damage, their chins tend to get weaker (see Gaetche, Chuck Liddell, Anderson Silva) * Alertness/awareness/technique: This part is the more conscious effort by the fighter to reduce damage. Generally fighters well-versed in boxing or have great alertness generally can take a shot better than others. They tend to roll with their shots reducing the impact (and therefore whiplash) of the strike. This can be seen easily by how sucker punches are very effective, but punches against an alert opponent are significantly harder to knock out with. Does anyone have further input? Remember that the topic is about durability, not recovery.