Can key presses be used to control image presentation?

[clawton]

I would like to know whether there is any way to allow participants to use key presses within either MediaLab or DirectRT to control presentation of images in a sequential manner and then record which image is finally chosen. For example, to test people's susceptibility to the Muller-Lyer illusion, I would like to be able to present images of lines in a sequence like this: >-----<-------> then >------<------> then >-------<----->, where participants would be able to advance or go backward between the images by pressing a key (e.g., right and left arrow keys), and then record which image they choose as their final answer (the goal being to choose the drawing where the line segments between arrows appear equal). Ideally, I would like participants to be able to drag the middle arrowhead to the position they think equally subdivides the line, but I don't know how to program animations that participants can control, so I thought having them control presentation of still images might work instead. Any suggestions on how I can do this would be greatly appreciated!