Track the resizing of a circle?

[I][edited from support email][/I]

I have a situation where I want people to first see a focal stimuli (e.g., a circle). Then, I want them to attempt to replicate the size of the circle on a subsequent screen (the DV here is deviation from the actual size).

I’ve been pondering how to do this in MediaLab or DirectRT. One solution I cam up with is to simply to present an image on the next screen consisting of 9 different possible choices and asking them which is closest using a 9-point scale. The limitation here is that I worry about people gravitating towards the middle value. Now, I could create various images so that the true value occupies different positions in the chain, and this might work if there are no other options, but I wanted to check if there was another possibility. I came up with two ideas, but I don’t know if they can be implemented in medialab or DirectRT…figured if they could you would know.

1) Is there a way to have people draw a circle using paint’s or powerpoint’s circle tool? That would create a truly continuous measure of deviation, which would be pretty cool.

2) Is there a way I could have 12 different images where people could cycle up or down through the images and then pick the one that they think is best? Perhaps
the starting image could be random, which reduces concerns about people knowing (or at least visually seeing) the midpoint of the scale.

Any thoughts? As I said, I probably have a solution that will work (presenting assortments of images), but I thought if there was a better way to handle this in MediaLab or directRT you would know.

Thanks for your help!

I would use the WebTracker item type in MediaLab. Make 12 simple html pages each with a variant of the circle. Each has a bigger & smaller link that takes you to the next or previous circle. You could do it as a custom item too or with java but this would be a quick way to get it done.

[I][edited from follow-up response][/I]
[quote]
You’re a clever one, Blair Jarvis. Clever indeed. That’s actually even better as I can see how much they vary the circle before reaching their final decision!!!
Thanks a million![/quote]

:)