Asking questions changes behavior: Mere measurement effects on frequency of blood donation.

OBJECTIVE: This research examined the impact of completing a questionnaire about blood donation on subsequent donation behavior among a large sample of experienced blood donors. DESIGN: Participants (N=4672) were randomly assigned to an experimental condition that received a postal questionnaire measuring cognitions about donation or a control condition that did not receive a questionnaire. MAIN OUTCOME MEASURES: Number of registrations at blood drives and number of successful blood donations were assessed using objective records both 6 months and 12 months later. RESULTS: Findings indicated that, compared to control participants, the mean frequency of number of registrations at blood drives among participants in the experimental group was 8.6% greater at 6 months (p<.0.007), and was 6.4% greater at 12 months (p<.035). Significant effects were also observed for successful blood donations at 6 months (p<.001) and 12 months (p<.004). CONCLUSION: These findings provide the first evidence that the mere measurement is relevant to promoting consequential health behaviors. Implications of the research for intervention evaluation are discussed.