In the late 1910s, behavioral scientist John B. Watson was studying whether emotional reactions could be conditioned in humans, after the manner of Pavlov’s dogs. One of his subjects was a baby named Albert, aged nine months. Albert was exposed to a series of stimuli, including a white rat, a rabbit, a monkey, masks, and burning newspapers. Initially, Albert showed no fear of any of these objects. Then, as Albert was exposed to the rat, Watson made a loud noise by hitting a metal pipe with a hammer, whereupon Albert cried. After being repeatedly presented the white rat followed by the loud noise, Albert began to cry as soon as he saw the rat.

   Watson must have conducted the experiment many times because he collected enough data to discover that not only did the kid cry at white rats, but he also began to cry at anything that might possibly look like a rat, including a variety of white objects and an equally large assortment of furry objects (including, at one point, a Santa Claus beard). Even those objects which he had previously played with began to frighten him if they bore any resemblance to a rat (or if they were handed to him by a man wielding a hammer).

   Watson didn’t bother to decondition Little Albert at the end of the experiment, and it is unknown whether his fear of white rats, loud noises, or psychologists remained with him. Sadly, Albert died at the age of six. It is unknown whether his mother, who was paid a grand total of $1 for his participation, ever realized what they were doing when they came to play with her son.