This question refers to the experiment famously known as "Little Albert experiment". It was conducted in 1920, by Watson and Rayner, two American psychologists. The experiment studied the phenomenon of classical conditioning, where a conditioned stimulus (a loud noise produced by a hammer) is paired to an unconditioned stimulus (a sweet furry animal) until they produce the same result. The scientists used for their experiment a 9 months old baby, little Albert. According to our standards today, this is unethical since Albert was not protected by all this trauma induced by this constant state of fear. Also, Albert's psychological welfare after the end of the experiment was never restored.