Which tests should I use - please help

Hello. First-time poster here. I've been having trouble trying to figure out how to analyze some data, and I would really appreciate some help.

I've collected response rates in thirty-two cells to between three and twenty-one presentations of two pairs of stimuli for each cell. The two pairs of stimuli were not the same for each cell, but each cell was presented with two of the same four possible pairs.

I would like to determine whether the variability (or stability) of a response across trials is determined by the stimulus quality presented, the specific stimuli presented, or the cell. I'm not sure what kind of test I should use when variability itself is my dependent variable, and not just a nuisance.

I would also like to determine whether response magnitudes across trials correlate better (within individual cells) for stimuli belonging to a pair than for stimuli belonging to different pairs.

Thank you all for reading this far, at the very least; and many, many thanks to anyone who can help me out a little. I've tried to be as clear as possible in my description of the problem, but let me know if something I wrote doesn't quite make sense.