buying a computer screen for running e-prime experiments

[Eva Pavlinusic Vilus]

Hi everyone,

Sorry for such a banal question, but my lab (psycho/neurolinguistics) is currently purchasing equipment and we need to buy a computer screen for the computer that will run experiments in E-prime. Which specifications should we look for? A gaming-sort of thing or a more regular type? We will use EEG as well and do ERP experiments (Brain Products system), so I guess the screen should not be too large in order to minimize the eye-movement artifacts? I haven't found the answers in E-prime documentation, if you can point me where to look for them, I would really appreciate it. 

Thank you!

Eva

[Spape, Michiel]

Hi Eva,

Really interesting question, I wish we would have something in the E-Primer or indeed in my Psychologist’s Guide to EEG, covering contemporary PC screens. What you need to look for might well be found in a gaming-sort of thing, here’s some specs:

• Get something with a very high refresh rate for your EEG experiments. LCD screens almost always used to be 60 Hz, now they go way up to about 240 Hz. That will change the upper limit of your precision to just over 4 ms (vs 17 ms in 60 Hz).
• You used to have to worry about black-to-light and light-to-blank speed of LCD screens, but I cannot really imagine that would be a big thing at 240 Hz. Still, they tend to call this sort of thing ‘response time’, which should be 1 ms or less nowadays (much shorter than a cortical ERP).
• Big screen: of course, why not? Don’t try to minimise eye-movement artifacts by having poor quality, just move your subject away from the screen, which might also reduce the electric interference. Remember, the only point for the eyes to make movements is not the physical distance between two pixels, but the angle between them. Of course, if your lab is too small to allow for a big screen at 1 m instead of a small one at 50 cm, that’s another matter.
• You might also use a projector for getting rid of that problem entirely, but the problem with that is that their contrast isn’t as high as LCD screens, and their refresh rates are typically still quite low because they are rarely used for anything needing high refresh rates (e.g. powerpoints and perhaps movies). Not that gaming requires high refresh rates, IMHO, but lucky for us, gamers seem to think it does.

Hope that helps! I’ll be eager to learn what you will buy and what the result will be and how E-Prime copes. Note that the higher the resolution and refresh rate, the higher the demands on the graphics processing, and the higher the timing error, so make sure to test things! Of course, if that becomes a problem, you can always run things at a lower resolution and probably refresh rate.

Best,

Michiel

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[Eva Pavlinusic Vilus]

Thank you for such a detailed reply, it really helps! We'll take into consideration everything you wrote and hopefully find the right screen. Also, it would be really useful to be able to find these information for other new labs as well, maybe you could write a few lines on your blog or in the book, if you republish it?