Monday, October 18, 2010

A home-made file for converting the visual angles into metric size on your computer screen

Hi folks !

I know that, once again, it's been a (long) while since I wrote something. I am really busy because of my last exams, my thesis that I have to start finish and my search of a kickass... good... descent... a job.

In the meanwhile, here's a excel file I just created for those who'd like to have a visual angle convertor.
Indeed, when you're designing an experiment running on a computer, and that you're presenting visual stimuli, you'll have to control the size of the items.
In the literature, they speak about "visual angle". Imagine that,you want to replicate a study where they presented a 2 cm long word on the screen and where the subject sat 60 cm away from the screen. But in your experimental room, they'll have to sit 100 cm away from the screen. You'll have then to adjust the size of the words in order to be perceived as well as the original experiment.

So here are your choices :
- you already have a convertor for that kind of calculations (provided by your super-promotor)
- you like mathematics and you wanna understand why using trigonometry is in fact useful ? (remember the Tan and ArcTan back in secondary school ?)
- or you're lazy and you want to find a program that somebody else did to compute the informations you need (hint : choose this choice).

For downloading it, just click here.

Just enjoy, good luck with your experiment and see you next time.

N.B. : sorry if the few words in the excel file are not that clear or more "frenchy", I originally did it for me... Also, the angle values are in degrees.
N.B. 2: I'll write a short article about divided visual field methodologies next time because I've been shocked to discover the incredible number of studies that did everything and anything but what they should have done... If you're eager to know it, just check the article of Bourne (2006). The divided visual field paradigm : Methodological considerations, Laterality, 11, 373- 393.