All sorts of medical studies ask strange things of their guinea pigs. Taking new pills, sleeping, not sleeping, changing their eating habits.
But I hope the compensatory indemnity was high for the group who volunteered to have their sexual arousal monitored by taking readings of their penises, in a study to show whether circumsized men are less sensitive. The conclusion: they’re not.
I hope they didn’t tell the subjects they were monitoring penis sensitivity, or it would contaminate the sample with bias — but they probably had to due to ethics rules.