Watson conditioned a baby to fear everything — and never undid it

In 1920, Johns Hopkins University psychologist John B. Watson and graduate student Rosalie Rayner conducted an experiment that would become infamous in the history of psychology. They selected a 9-month-old infant, known as 'Albert B.,' and placed him in a controlled environment where a white rat was presented alongside a loud, jarring noise — a steel bar struck with a hammer behind his head. After several pairings, Albert cried and tried to crawl away at the mere sight of the rat. The fear generalized to other furry objects: a rabbit, a dog, a fur coat, and even a Santa Claus mask.

Watson and Rayner planned to later decondition Albert, but he left the hospital at about one year of age before they could do so. Watson never followed up. The conditioned fear was never extinguished. For decades, Albert's identity was unknown, and the experiment was taught as a pioneering demonstration of classical conditioning in humans — with a footnote about the ethical issues of not reversing the conditioning.

In 2009, researchers identified Albert as Douglas Merritte, who had severe hydrocephalus and neurological impairments from birth — conditions Watson either did not know or did not disclose. Merritte died at age 6. The revelation added a deeper ethical dimension: the subject was a vulnerable child with a medical condition, experimented on without informed consent from a parent who could not have understood the risks. The experiment violated nearly every modern ethical standard for research with human subjects.

The Little Albert experiment became a canonical case in research ethics education, illustrating the necessity of informed consent, the right to withdraw, and the obligation to undo harm caused in the course of research. It contributed to the regulatory framework that would become the Belmont Report and institutional review boards — though Watson himself faced no consequence for the experiment, and left academia for a career in advertising.