input to canvas

[Wendy Davidson]

Hi
I was hoping someone could give me some advice about using the canvas 
object.

I have designed an experiment in which a dot moves along the screen (using a 
copy from off-screen canvas at refresh) and I need to add input to it.  
Basically, the subject must press the keyboard to indicate if the dot is the 
same or different as before.

Does anyone know if it is possible to add input to a canvas object?

Any help on this would be great!

Thanks

Wendy Davidson
University of Aberdeen