Classical conditioning (also Pavlovian or respondent conditioning, Pavlovian reinforcement) is a form of conditioning that was first demonstrated by Ivan Pavlov

Ivan Pavlov

Ivan Petrovich Pavlov was a famous Russian physiologist. Although he made significant contributions to psychology, he was not in fact a psychologist himself but was a mathematician and actually had strong distaste for the field....

 (1927). The typical procedure for inducing classical conditioning involves presentations of a neutral stimulus

Stimulus (physiology)

In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....

 along with a stimulus of some significance, the "unconditional stimulus." The neutral stimulus could be any event that does not result in an overt behavioral response from the organism under investigation.