A research design where neither participants nor researchers know who is receiving the experimental treatment versus the control condition. This method prevents both participant and experimenter expectations from influencing the results.
The term 'double-blind' emerged in medical research in the 1940s, combining 'double' (meaning both parties) with 'blind' (meaning unaware). It evolved from earlier 'single-blind' studies where only participants were kept unaware, as researchers recognized that investigator bias was equally problematic.
The double-blind method was actually inspired by wine tasting competitions in the 1800s, where judges' cloth hoods prevented them from seeing the wine labels. Modern pharmaceutical companies spend millions creating identical-looking sugar pills that are indistinguishable from real medications, sometimes even adding bitter flavoring to match the taste of active drugs!
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