From the website that this lab is based on...
Hemispheric specialization theory says that certain tasks can be processed by the right hemisphere or by the left hemisphere. If the information that arrives in a hemisphere can be processed by that hemisphere, then the response time will be shorter and the processing will be more accurate than if the information cannot be processed by that hemisphere and must be sent, via the corpus callosum, to the other hemisphere.
Based on these accuracy and response time measures, it has been found that the left hemisphere appears to be specialized for verbal tasks while the right hemisphere is specialized for spatial tasks.
Try the link before you buy...
When my students tried this lab almost no one got a statistical difference between the hemispheres. So this might not be the best lab for showing differences...but if you value demonstrating no difference (at least on this task) then this lab is for you.