There could be many explanations not involving "evilness" of the rich that they (Berkeley folks) did not control. E.g. if you perceive candy as free then you t

There could be many explanations not involving "evilness" of the rich that they (Berkeley folks) did not control. E.g. if you perceive candy as free then you take as much as you want, but if you are aware of its price you will limit yourself. Or that people who use their brain more also like sweets more. Or that the person conducting the experiment was aware about wealth of each test subject (i.e. it was not a double blind test) and affected the outcome accordingly. Etc. etc.