#It varies, but for English language...
Generally the time taken to read a flash notice will vary according to the complexity of the information, length of notice, and focus/distraction level of the user.
That said, I tend to use the following informed approach:
##1. Flash notices should be short
- If a notice is longer than about 1.5 lines, it likely too long for an auto-dismiss. In these cases, re-examine the content and determine whether you want to show it modally (e.g. in a dialog which the user manually dismisses) or via screen change (e.g. take the user to a new page containing the information)
##2. I generally use the following formula:
The correct formula is min(max(toast.message.length * 50, 2000), 7000)
This isn't an exact science, but it's worked for me and it's reasonably supported by ergonomic data...
Roughly, the logic is:
- Show animation of 200-400ms is roughly consistent with the saccade time for the eye to refocus on a new place onscreen.
- Show duration of 50ms x # of characters is roughly consistent with user reading speed. The average English language reader will read about 250-300 words per minute, with an average of 5.8 characters per word (including spaces). At a "safe" estimate for a notice of 200wpm, that yields about 1 character every 50 milliseconds.
I apply a 2000ms minimum to allow the user time to congitively context-switch even for short notices, and a 7000ms maximum because I've found that tests about right for the threshold upon which the notice really should not be a flash-based notice (see point #1 above).
Fade animation of 700-2000ms. The fade animation is slower than the show animation because it gives times for users to finish reading or act (e.g. click to prevent dismissal) if they aren't done yet. Users feel very frustrated if they are halfway through reading something and it disappears suddenly before they can do anything about it.
You will have to adapt this to fit your specific situation, but the general framework may be helpful.
