Re: reaction time measures (Pawel Kusmierek )

Subject: Re: reaction time measures
From:    Pawel Kusmierek  <pawel.kusmierek@xxxxxxxx>
Date:    Fri, 8 Jun 2007 10:02:16 -0400

I know that people are happy with Presentation . I am not sure how well it does handle timing of visual stimuli, though you will probably have some idea if you read through their online documentation. It maybe also informative in general way. Keep in mind that timing of responses in one thing. The other thing is timing of stimulus delivery - for visual stimuli you basically have to be able to know when the frame display occurred. With typical refresh rate of 60 Hz you will get an error of up to 16 ms, if you don't look into this. For this reason, I know people who decided to use LEDs rather than fiddle with the display frames. Which is of course only possible if you are happy with _very_ simple stimuli. Similarly, if your program plays a sound under windows, the playback latency will be around 20 ms unless you know how to bypass or circumvent standard windows sound engine. Nevertheless, it is possible to get ~1ms accuracy under windows, as shown here (go to Timing>Uncertainties) and here (see Timing capabilities example ). Good luck, Pawel -- Pawel Kusmierek PhD Department of Physiology and Biophysics Georgetown University Medical Center The Research Building WP23 3970 Reservoir Road NW Washington, DC 20007 phone: +1 202 687-8851 or 8028

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