03.21.08
Resp…..onse time
I read the paper “Miller, R. B. (1968). Response time in man-computer conversational transactions.” in my first year university.
The basic advice regarding s/w response times has been about the same for forty years.
- 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. Normally, no special feedback is necessary during delays of more than 0.1 but less than 1.0 second, but the user does lose the feeling of operating directly on the data.
- 10 seconds is about the limit for keeping the user’s attention focused on the dialogue. For longer delays, users will want to perform other tasks while waiting for the computer to finish, so they should be given feedback indicating when the computer expects to be done. Feedback during the delay is especially important if the response time is likely to be highly variable, since users will then not know what to expect
When I was a product manager at Symbian, I would use these values to offer engineers a guide as to pefromance of software. (often there were no explicit peformance specifications).
Mobile phones and other consumer electronics fall are particularly sensitive to the reponse time contraints. It’s very frustrating to use a TV remote control with a half second lag.
Mobile phones tend to command our attention so that when playing with one, a time lag appears long since the user is staring at the screen, waiting for something to happen.
So, bear these values in mind when designing a system. And remember, give engineers a problem to solve and they will find a way – so long as you make it a high priority requirement.
Donald Knuth confronted a slow startup time of TeX with a novel solution – he launched the program to a startup state and then took a core dump of the application process and used an utilit which would reanimate the coredump, thus avoiding the startup code completely! Smart.