Controlled experiment: advantage: provides context for addressing whether or not an effect is real and which theoretical account explains it, disadvantage: eliminate other sources of influence. Participant observation: researcher becomes an observer and participant of the situation and learn the dynamic of the setting. Sales people, lobbyist, politicians: their livelihood depends on it. Robert cialdini found that the key to successful influence is what we do before attempting to influence: was a sales man for 3 years. Questionnaire with a cheque or questionnaire with the fact that you will get a cheque after. 78% of the people who got the cheque right away did the questionair. 66% of the cheque later group responded. Give them something in advance, and then they have to reciprocate. Door-in-the-face technique (or reciprocal concessions procedure: study. Majority of people responded back to a complete stranger: companies send you self label stamps asks for a donation.