That little jump or start (as in, "You gave me a start,") is called the startle response. It causes the eyes to blink and the arm and leg muscles to contract convulsively. It happens very quickly (e.g., eyeblink response in 21-75 milliseconds).
Repeated exposure to startling stimuli can even train you to anticipate the startle response. On the shooting range, we call it flinch.
You can learn to consciously eliminate a flinch because the flinch itself is a learned response. And there are those who claim to have overcome the startle response, but there is some controversy over whether that is really possible, since it is a reflex, and also since a small percentage of the population have a very weak or even no startle response to begin with.
Until recently, researchers associated startle response only with loud noises or visual stimuli such as sudden movements toward the face. A 2001 study at the University of Toronto, however, demonstrated "that startle is best evoked when noises are combined with tactile stimuli . . . ." This led to the conclusion: ". . . that the primary role of the startle reflex is to defend the body against strong impact stimuli, not noises."
Therefore, the startle response has a key role to play in self defense. Rather than try to extinguish this response that's hardwired into us from before birth, we need to ask how we can understand it and cooperate with it in our defense training. Let's begin by taking a look at the startle response at its fullest expression.
When fully startled, you will go into a partial crouch (leg contractions), bring the head down (rounding the back & protecting the vital organs) and bring your hands up to the sides of your face (hands protect the head & elbows protect vital organs). This is your base for self protection, and it's automatic.
In self defense training, it is best to practice a ready stance very close to that of the startle response. With hands open, raise them -- palms facing away from you -- to chest level. Elbows should be against the ribs. This is a position someone might naturally assume when trying to calm an angry, aggressive person. I can hear him saying, "Okay, okay, can't we just talk about it?"
This position readies you to go into the defensive Startle Response Posture (SRP). Your body is almost there, but not quite. This will shorten your response time. (As an aside, some combat pistol trainers acknowledge the SRP and teach their students to fire from the "combat crouch" posititon.)
When you deem it necessary to assume a ready stance, we may conclude that you are in a situation of perceived danger. This means that you will already have some level of adrenaline coursing in your veins. That's good because, as one study found, ". . . threatening situations or fearful experiences have a powerful augmenting influence on the startle response." Your automatic response will not only be quicker, but the adrenaline will enable you to launch your counterattack directly from the SRP with ferocity.
Rather than try to resist or extinguish the startle response, I believe it will be much more productive to train yourself to launch palm heel strikes, judo chops, elbows and low kicks from the SRP. This is something that most martial arts and self defense programs do not teach. I do, however, own a 2-video set of a self defense system that actually begins every move from the startle response.
I might tweak the final product a little here or there, but overall, it's better than a lot of what passes for self defense training. It's called "Self Defense by the Numbers." It was produced by Century Martial Arts, but it's no longer available." It probably never caught on because it was based in real-world simplicity with no bells, whistles or flashy techniques. You may be able to find old VHS copies on eBay.
There are a couple of other systems that build on the startle reflex, and although they have good reputations, I have never really examined their products, so I won't mention them here.
Bottom line: train the basics & integrate them into the SRP.
I will continue this discussion in Startle Response, 2