One of psychology’s darkest human experiments: ‘Little Albert’ terrified for science in infamous 1920 study

Between 1919 and 1920, John B. Watson and Rosalie Rayner conducted a controversial experiment at Johns Hopkins, conditioning fear in an infant who could not consent. Exposed to a white rat and loud noises, the child developed lasting fear responses that spread to other objects. By today’s ethical standards, the study is condemned as one of psychology’s darkest episodes, highlighting the dangers of harming vulnerable participants.