A fewhoursaftergivingtheratseachsubstance, researchersapplieddifferentlevelsofpressuretotherats' headsandlookedforsomekindofresponsethatindicatedtheratsfeltthepoke.
In a classic 1994 studyoutofSweden, researchershadtenmenfastovernight, thengavethemeither a moderatedoseofalcoholonanemptystomach, orfedthem a heartybreakfastalongwithit.
Andthenumberofcigarettesmattered—aslongastheparticipantsdrankabove a certainamountofalcohol, moresmokinglentitselftomoreseverehangoversymptomsonaverage.