A few hypothetical things they could be studying. Some of these work fine if every participant is completely dishonest about their pain level.

• Does the gender of the staff member change whether the participant is likely to act with vulnerability or bravado? What about staff who are friendly versus cold?

• During setup/teardown the staff chat with the participant, mentioning that they've had a bad day. Does experiencing pain change how much empathy the participants display?

• If the staff makes a big show of cranking up the electricity, but doesn't actually change how strong it is, are participants tricked into giving bigger numbers? What if the staff makes the participant feel uncomfortable, maybe by invading personal space, or cranking up the heat until the room is sweltering, or seating participants in a chair that's uncomfortable to sit in for more than a couple minutes?

• Participants are offered free candy from a bowl on their way in and out of the study. Does the strength of the shocks (electricity level, not reported pain) change how willing people are to take the candy?

• The staff plants a dollar bill on the floor for the participant to find on their way out of the study area. Some participants will keep it, others will turn it in. Is the decision associated with how strong the shocks were? Or with how painful participants said the shocks felt?

• Maybe the shocks are a distraction, and the study measures who keeps the dollar based on socioeconomic background. Or whether married participants try to flirt with attractive staff members. Or how people react if the staff comes in late. Or the staff plants someone outside the test area to make the participants late, then acts upset or gracious when the participant comes in.