Lost Letter Technique

The lost letter technique, introduced by Milgram, Mann, and Harter in 1965, is an unobtrusive field method for measuring community attitudes by exploiting a small act of everyday helping. Researchers distribute stamped, addressed envelopes in public places as if they had been accidentally dropped, with the letters addressed to different organizations representing varying causes (for example, a neutral individual versus a politically charged group). A passerby who finds a letter must decide whether to mail it, ignore it, or destroy it, and the proportion of letters returned for each addressee serves as an index of public sentiment toward that cause -- letters addressed to favored organizations are mailed more often than those to disfavored ones. Because finders do not know they are participating in a study, the measure sidesteps social-desirability bias and yields a behavioral, aggregate indicator of attitudes that complements self-report surveys.