We've been going round and round on this topic on other threads. So I thought I would try to make it clear what I'm talking about to clarify, and also present the topic for those who haven't been following the other threads.

A basic premise in modern sports science is that you need to isolate a physical movement to develop and perfect it. An example is a tennis player that is having trouble with his or her backhand. A good coach will take that player aside, feed them the ball over and over and make them focus on and work on their backhand until it improves. Then the player takes it back into his or her game in a more random fashion. Our colleagues in combat sports do this all the time as well. Boxers work on drills to develop their jab....everything from practicing against a stationary heavy bag, to practicing against a moving partner using a focus mitt, to practicing against a partner actively trying to hit them. I'm sure we can all think of similar examples from BJJ, MMA, and Thai boxing. The idea is to isolate a skill or technique you want to work on in a 1:1 drill format so you can really concentrate on it. Of course the danger of taking this too far is that you can get "motorset." In other words, you have memorized a specific response to a specific attack. Then in application the opponent doesn't do exactly what you expect and you "freeze" momentarily because you don't have a response for it. So you have to mix up the training, start specific and then make it more and more random. And then you have to go back and put it into a "live" situation like sparring or Chi Sau. It is part of progressive development. I'm wondering how many people train their Wing Chun this way? Here are some examples of people that do:

From Duncan Leung’s lineage:

http://www.youtube.com/watch?v=3UlBm7PJlWs
http://www.youtube.com/watch?v=Qr1cdWIbcpc

From Alan Orr:

http://www.youtube.com/watch?v=yjd3abCoiaA
http://www.youtube.com/watch?v=hghI_aLTkvI

From Ernie Barrios:

http://www.youtube.com/watch?v=_euVrjyso54
http://www.youtube.com/watch?v=fZQP3ig3seI

Before anyone gets all excited, keep in mind that these are drills meant to develop specific techniques and attributes. This is not fighting. But this is how fighters train.