Re: Flinch Response in Aikido
I'll just get a bit more aikido technique specific, if I may. Ikkyo undo exercise can be performed as 'flinch response', so I guess I'm arguing that the flinch can be trained, at least a bit.
At the range we generally practice aikido, our ikkyo undo 'flinch' is clearly made to meet the attack/attacker. However, even when we flinch away from a surprise attack, part of us (ki, intent or tegatana) can and should go to meet the attacker. So think this going-to-meet response is good to train as a flinch - an irimi-flinch.
I like to do ikkyo undo exercise with hips oblique rather that square as it is more realistic. Experimenting with footwork during the exercise shows how versatile the it can be. Also, breathing in is a natural flinch response, so breathing in on the up will hopefully leave us in a good position to apply a technique (a key point of Bauer's) on the down/out.
I would have thought that the better we get, the briefer our flinch becomes before technique kicks in - until, a very long way down the road, one's 'flinch' becomes the calm pre-emptive initiation of a technique.
Because, in aikido, we are training ourselves to not clash, a sudden flinch can cause an attacker to brace himself for a resistance that doesn't happen. The resulting surprise will hopefully give the initiative to us. This is how I think a flinch-response could be successful against a blade - you might flinch, then immediately move to prevent the blade from penetrating.