Lost Letter Technique
Also known as: Lost-Letter Technique, Dropped Letter Method, Return-Rate Attitude Measure
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.
Key highlights
- Unobtrusive and behavioral, avoiding social-desirability bias.
- Enables geographic comparison of community attitudes.
- Simple and inexpensive to deploy at scale.
- Provides a candid aggregate indicator complementing surveys.
Intuition
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How it works
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When to use it
Use the lost letter technique when you want an unobtrusive, behavioral measure of aggregate community attitudes toward causes or groups, free of social-desirability bias and capable of geographic comparison (for example across neighborhoods or regions). It is valuable for sensitive political or intergroup attitudes where surveys are suspect. It is less appropriate when individual-level attitudes are needed (it yields aggregate rates), when ethical or legal concerns about distributing mail arise, or when low and noisy return rates make precise estimation difficult. Careful matching of letters, randomized distribution, and adequate numbers across locations are essential, and modern variants include lost emails and online analogues.
Strengths & limitations
- Unobtrusive and behavioral, avoiding social-desirability bias.
- Enables geographic comparison of community attitudes.
- Simple and inexpensive to deploy at scale.
- Provides a candid aggregate indicator complementing surveys.
- Yields aggregate, not individual-level, attitudes.
- Return rates are low and noisy, requiring many letters.
- Confounds such as location traffic and finder characteristics can bias results.
- Raises practical and ethical questions about distributing deceptive mail.
Common pitfalls
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Applications
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Frequently asked
How does the lost letter technique measure attitudes?
Researchers drop stamped, addressed letters in public as if lost, with letters addressed to organizations representing different causes. Finders decide whether to mail them, and the return rate for each addressee indexes community sentiment: letters to favored causes are mailed more often than letters to disfavored ones, giving a behavioral, unobtrusive measure of attitudes.
Why is it considered unobtrusive?
Finders do not know they are participating in research; they simply encounter what appears to be a genuinely lost letter and make a private choice. Because there is no survey, no observer, and no awareness of being studied, the measure avoids social-desirability bias and captures behavior people would not necessarily report honestly on a questionnaire.
What are its main limitations?
It yields aggregate rather than individual attitudes, return rates are low and noisy so many letters are needed, and confounds such as foot traffic and the demographics of different locations can bias results. Careful matching of letters, randomized distribution across comparable locations, and large numbers are required to draw valid conclusions.
Sources
- 1.Milgram, S., Mann, L., & Harter, S. (1965). The lost-letter technique: A tool of social research. Public Opinion Quarterly, 29(3), 437-438.
- 2.Ross, L., Greene, D., & House, P. (1977). The 'false consensus effect': An egocentric bias in social perception and attribution processes. Journal of Experimental Social Psychology, 13(3), 279-301.
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Cite this page
ScholarGate. (2026, June 23). Lost Letter Technique. ScholarGate. https://scholargate.app/social-psychology/lost-letter-technique