The "Little Albert" experiment was a famous psychology experiment conducted by behaviorist John B. Watson and graduate student Rosalie Raynor. Previously, Russian physiologist Ivan Pavlov had conducted experiments demonstrating the conditioning process in dogs. Watson was interested in taking Pavlov's research further to show that emotional reactions could be classically conditioned in people.

The participant in the experiment was a child that Watson and Raynor called "Albert B.", but is known popularly today as Little Albert. Around the age of nine months, Watson and Raynor exposed the child to a series of stimuli including a white rat, a rabbit, a monkey, masks and burning newspapers and observed the boy's reactions. The boy initially showed no fear of any of the objects he was shown.

The next time Albert was exposed the rat, Watson made a loud noise by hitting a metal pipe with a hammer. Naturally, the child began to cry after hearing the loud noise. After repeatedly pairing the white rat with the loud noise, Albert began to cry simply after seeing the rat.

Watson and Raynor wrote:

The instant the rat was shown, the baby began to cry. Almost instantly he turned sharply to the left, fell over on his left side, raised himself on all fours and began to crawl away so rapidly that he was caught with difficulty before reaching the edge of the table."

This is a classical conditioned stimulus and response experiment. And this is quite similar to bullet theory.