[DMDX] Re: four response buttons At 03:49 PM 7/24/2003 +1000, you wrote:
>Dear users,
>
>I just started reading maunals of DMDX and have some problems.
>I want to run experiments in which I need four buttons or keys for subjects
>to press and measure the response time as accurately as possible.
>Is there any device which has four buttons and can measure RT with
>millisecond adduracy?

   Many USB gamepads have four or more buttons.  Timing on them is usually 
superior to KBs and there's certainly much less variability from one to the 
next than there is between one KB and the next.  USB 2.0 gamepads stand a 
distinct change of having millisecond accurate timing but I've yet to get 
the chance to benchmark one.

>If keyboard is the only possibility for four buttons, how can I make errors
>as small as possible?

   You would have to have a method of measuring the error and even then 
you'd have to keep on trying different KBs until you found a good one.  I 
was pleasantly surprised to find that a new one the other day that someone 
needed for testing that only had a SD of 4.5 ms.

>Is there any way of knowing the range of errors?

   You have build something that presses keys at exact an interval, then 
you can use testmode 8 to benchmark a keyboard.  But most people don't have 
the wherewithal to build crystal controlled oscillators driving a solenoid...

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