The Lost-Letter Technique
Another of Milgram’s contributions is a method for doing unobtrusive surveys of political opinion. The method is called the ‘‘lost-letter technique’’ and consists of‘‘losing’’ a lot of letters that have addresses and stamps on them (Milgram et al. 1965).
The technique is based on two assumptions. First, people in many societies believe that they ought to mail a letter if they find one, especially if it has a stamp on it. Second, people will be less likely to drop a lost letter in the mail if it is addressed to someone or some organization that they don’t like.
Milgram et al. (1965) tested this in New Haven, Connecticut. They lost 400 letters in ten districts of the city. They dropped the letters on the street; they left them in phone booths; they left them on counters at shops; and they tucked them under windshield wipers (after penciling ‘‘found near car’’ on the back of the envelope). Over 70% of the letters addressed to an individual or to a medical research company were returned. Only 25% of the letters addressed to either ‘‘Friends of the Communist Party’’ or ‘‘Friends of the Nazi Party’’ were returned. (The addresses were all the same post box that had been rented for the experiment.)
By losing letters in a sample of communities, then, and by counting the differential rates at which they are returned, you can test variations in sentiment. Two of Milgram’s students distributed anti-Nazi letters in Munich. The letters did not come back as much from some neighborhoods as from others, and they were thus able to pinpoint the areas of strongest neo-Nazi sentiment (Milgram 1969:68). The lost-letter technique has sampling problems and validity problems galore associated with it. But it’s still an interesting way to infer public opinion about emotionally charged issues, and you can see just how intuitively powerful the results can be (Further Reading: the lost-letter technique).