What is the shortest perceivable application response delay?

Question

A delay will always occur between a user action and an application response.

It is well known that the lower the response delay, the greater the feeling of the appli

Answer 1

New research as of January, 2014:

http://newsoffice.mit.edu/2014/in-the-blink-of-an-eye-0116

...a team of neuroscientists from MIT has found that the human brain can process entire images that the eye sees for as little as 13 milliseconds...That speed is far faster than the 100 milliseconds suggested by previous studies...