Create a experiment with dots appearing random on a screen

[nyu.nirs at gmail.com]

Thanks a lot for your response!

So I think I get what you are saying.

And these zones you talk about, would that be images on a slide or is
there another way to do it?

Further, if we want to keep the ratio between the two different types
of dots to either 1:1, 1:2, 3:4, or 5:6, is there a way I could do
that?

A lot of problem solving in creating this project and it is driving me
a bit bonkers. Ugh.



On Mar 5, 3:52 pm, David McFarlane <mcfar... at msu.edu> wrote:
> I recently contemplated this very problem while working on a spatial
> foraging task.  I am still a long way from implementing my planned
> solution, so I have no code to show, but allow me to sketch out my strategy.
>
> In short, I plan to first divide the screen up into a number of
> non-overlapping zones.  If I have at least as many zones as I have
> dots, then I can put each dot into a random position within its own
> zone, and that will guarantee that no dots overlap.  Dots in adjacent
> zones might still touch each other and form "clumps", but if I wanted
> to avoid that then I would just add a limit to where each dot could
> go within its own zone.
>
> If I make exactly as many zones as dots, then the dots will disperse
> about the entire screen with some degree of jitter between the
> dots.  If I want to allow for greater jitter across the screen, I
> could create more zones than dots.  In that case I would put the
> zones into a list, shuffle the list, then pick the first nDots zones
> for my dots, and then put each dot in a random place within its zone
> (perhaps with a limit as described above to prevent dots from
> toucing).  This would then allow some degree of clumping of dots
> across the screen.  In fact if I were serious about this I would
> parameterize it all so that I could easily reuse and control the
> procedure, something like GrowLandscape( nItems, nZones, zoneBuffer ).
>
> Looking at this in a more theoretical and general way, we can
> separate the solution space into three domains, nZones < nDots,
> nZones = nDots, and nZones > nDots.  nZones < nDots leaves the
> possibility of dots overlapping; nZones = nDots prevents overlapping
> dots and produces the most even dispersal of dots across the screen;
> and nZones > nDots also prevents overlapping dots, while allowing for
> greater jitter overall and the possibility of some clumping.  In the
> limit, nZones = 1 is just your current situation and has the most
> problem with overlap, while nZones = nPixels prevents overlap while
> allowing for the greatest jitter and clumping.  Sor for your
> puprposes I think you want nZones somewhere between nDots and nPixels.
>
> I hope this helps somewhat, at least I enjoyed documenting this for
> myself.  I at least would be very interested to learn what you come
> up with, so please post back.
>
> -- David McFarlane, Professional Faultfinder
>
> >Hi,
>
> >we are trying to create an experiment in eprime where participants
> >will see purple and green dots for 500 ms on a screen. Their job is to
> >determine whether their was more purple or green dots presented to
> >them.
>
> >The dots will be various size, however, we do want the area covered
> >(i.e. pixels) to be the same between the different colored dots even
> >though you might see e.g. more purple dots than green. The maximum
> >dots shown for each color is 15.
>
> >We have tried to created the experiment for a while, however, we keep
> >on running into a couple of issues.
>
> >1) The dots overlap each other
> >2) We have to manually make a list for each dot and then have it run
> >random during the experiment, however, this is very tedious as we can
> >have up to 32 dots and thus 32 list for a screen.
>
> >Anyways, appreciate any help we can get.
>
> >Thanks!
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