Another instinctive response to something flying toward the face is to turn the face away and duck the head. This is also not good to do while sparring. Looking away from a fist will not make it go away. To stop the fist, we must be able to see it. We must train ourselves to face threats and make appropriate responses.
When we are suddenly frightened or hear a loud noise, we instinctively freeze. This was a good defense when an animal that depended on movement to see prey, such as a rhinoceros, was attacking. However, nowadays, freezing in the middle of a crosswalk when a truck horn sounds is not a good idea. It is also not a good thing to do when an attacker jumps out of the bushes. Just as in sparring, your best bet of making a successful attack is when the opponent is attacking. At that moment, they are vulnerable and they are not thinking about defense. The freeze response is practically useless, unless you are tracking game or sneaking up on a sentry, so we need to train ourselves to react, not freeze.
Another instinctive movement that occurs when suddenly frightened or a loud noise occurs is to flinch. This is movement enables the body quickly to respond to an attack. However, due to the lack of our experience in defending ourselves daily, most people have no idea what to do in response to attack other than to flinch. With training, the flinch may be used to trigger an immediate response to a threat.