Benchmark wizard dots_circle and dots_square values

[Sarah Clayton]

Hi,

I'm running PsychoPy version 1.82.02 on Windows 7. I have two identical laptops that I want to use to run an experiment, but when I run the Benchmark Wizard different values are reported between the laptops for the dots_circle and dots_square items. On one laptop these are 800 and 900 respectively, and on the other they are 400 and 800. Every other value on the Benchmark Wizard is identical or at least very similar, except the laptop with the lower values for the above also has a 'piglet avbin import error'.

I'd be grateful if someone could explain to me what these values represent and if this will be a serious issue when running the same experiment across two laptops. If this is an issue, what might be causing the values to differ between laptops?

Although the two identical laptops were purchased together, one laptop was recently re-imaged by IT services at the university. To the best of their knowledge (and mine) everything was re-installed and should be identical...

Thanks in advance,

Sarah

[Jeremy Gray]

Hi Sarah,

The dots values are the number of dots that could be presented on screen without dropping a visual frame. Higher is better: more processing can be done within the 16.67ms time it takes to do one visual frame. 

It sounds odd that they differ. The only thing I can think of is that maybe the video card drivers differ. Be sure to download them from the manufacturer, not from Microsoft. Do not rely on Windows to tell you if the drivers are ok. Instead go to the manufacturer's website, and they can run a test and provide downloads (always free in my experience).

So does this difference actually matter? If you are using visually demanding stimuli (ones that are more complex), and its important that there is no visual jitter it probably does matter, or could. (If your computer can't keep up with what you are asking it to do, the visual frame will not switch and the same one will be visible for 33ms, which is called "dropping a frame". In dynamic displays, this looks not so smooth, and matters a lot in vision experiments.) 

So I would be sure the drivers are the same, and then try things out on the computer with lower dots_circle -- if things look fine there, they should also be fine on the other computer.

--Jeremy

--
You received this message because you are subscribed to the Google Groups "psychopy-users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to psychopy-user...@googlegroups.com.
To post to this group, send email to psychop...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/psychopy-users/71a0eb30-dac4-492a-b784-aef74c181ae7%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Sarah Clayton]

Hi Jeremy,

Thanks for your fast reply. The stimuli are all very simple- the tasks are mainly sums presented in text, or simple images of dots presented for the participant to compare numerosities. The main issue for us is that it records response time accurately across the two computers, but it sounds like this shouldn't be a problem with our stimuli.

I will check on the video card drivers though- thanks for this tip.

Sarah

[Jeremy Gray]

I agree that you will likely be fine, given that your stimuli are not dynamic. If the computer should drop a frame, no one would notice because the visual appearance is identical.

--Jeremy

To view this discussion on the web visit https://groups.google.com/d/msgid/psychopy-users/b5537a9b-dcbd-4059-b3b8-4dbb24acc1f3%40googlegroups.com.