frequency of cursor position recording

[Paul Groot]

Hi Ashtyster,

The sleep instruction simple puts the running script in 'idle'mode for
the specified number of milliseconds. Windows can use this time to
allow other processes to consume some CPU time. This construction is
often used in loops to prevent the system to become stalled. A
duration of about 20 milliseconds might be sensible on systems that
are connected to a display at 50Hz. The value could even slightly less
on systems with a typical refresh rate of 70-80Hz. However, windows
will probably update the mouse cursor position completely independend
of the refresh cycle, so the temporal resolution might be very
different...

Also, the DoEvent function is probably a leftover from the standard
basic language. It is used to allow other applications to handle the
message queue. I would normally not include this call in eprime
experiments.

best,
Paul

2011/3/25 Ashtyster <ashtyster at gmail.com>:
> Hi!
>
> I've gotten a bit confused trying to understand how to set the
> frequency of cursor position recording in E-Prime.
>
> I am presenting images and recording mouse cursor positions while
> subjects view the images. I would like to set the "sampling rate" for
> the cursor position recording to 50 Hz. The in-line script has the
> following sampling rate preset:
>
> 'Give some time back (required) - i.e. sampling rate.
> Sleep 20
> DoEvents
>
> What I am confused about is what does this '20' value mean? Does it
> mean 20 cycles per second?
>
> I would appreciate if somebody could answer this question.
>
> All best,
> Ashtyster
>
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