Feynman implies that psychology is a "cargo-cult" science where variations of experiments and assumed hypothesis are valued over scientific rigor or reproducibility. That's my guess too. See: misattribution of arousal studies, Millikan oil drop studies, Covid-19 and Didier Raoult Livre with hydroxychloroquine... etc. etc.

Edit: The article states B.F. skinner did create a box to remove these side-channel effects for rat experiments