In Human Computer Interaction and User Experience there's some oft repeated rules of performance:
- 0.1 second is about the limit for having the user feel that the system is reacting instantaneously, meaning that no special feedback is necessary except to display the result.
- 1.0 second is about the limit for the user's flow of thought to stay uninterrupted, even though the user will notice the delay....
- 10 seconds is about the limit for keeping the user's attention focused on the dialogue...
Card, S. K., Robertson, G. G., and Mackinlay, J. D. (1991). The information visualizer: An information workspace. Proc. ACM CHI'91 Conf. (New Orleans, LA, 28 April-2 May), 181-188.
Miller, R. B. (1968). Response time in man-computer conversational transactions. Proc. AFIPS Fall Joint Computer Conference Vol. 33, 267-277.
Myers, B. A. (1985). The importance of percent-done progress indicators for computer-human interfaces. Proc. ACM CHI'85 Conf. (San Francisco, CA, 14-18 April), 11-17.
However I can't access any copies of those articles. Also, frankly, they're all conference papers. Big HCI research often debuts at conferences, but ideally I'd like something robust which has been tested rather than something written 20-40 years ago for a conference.
One thing I've noticed is the "instant response" threshold quoted tends to be around 100ms to 200ms. Typical human reaction time is about 200ms so I'm wondering if there is a relation there. It seems possible; if something happens so quickly you can't react to it, it is practically "instant" in a way.
Approximately what length of time between action and reaction is perceived as instant by humans?