Narrator: Behavioral psychologists have come up with new views,
not only of animal behavior, but of human nature as well.
And these views all concern a process that we take for granted: learning.
Because we are all truly born to learn.
Ironically, one of the most important figures in the study of learning, Ivan Pavlov,
wasn't concerned with the subject at all.
At least, not at first.
Pavlov, a noted Russian scientist,
won the Nobel Prize for Physiology and Medicine in 1904.
As this original footage shows, Pavlov was initially interested in digestion
and the action of the salivary glands.
By diverting the saliva of dogs into test tubes, he could precisely measure
if and how much they salivated during digestion.
When food was presented, the dog salivated quickly,
an inherited salivary reflex.
But over repeated testings, a strange thing happened.
The dog salivated before contact with the food.
Just the sight of the food was enough to stimulate their drooling.
Then, just seeing the food dish, or even hearing the footsteps of Pavlov or his assistants,
was enough to trigger this built-in reflex.
What was going on to elicit this response?
Pavlov decided to find out, by systematically varying the stimuli
and measuring the dogs' reaction.
[Metronome clicking]
Metronomes, lights, and bells were all used as stimuli,
and they all worked as stand-ins for the food.
What mattered was not the kind of stimulus that was used,
but the fact that it reliably signaled that food was on the way.
♫ Electronic Music ♫
Pavlov had discovered a fundamental type of learning called "Classical Conditioning."
An original stimulus elicits an automatic unlearned response.
Both stimulus and response happen naturally. They are unconditioned.
Then a second, neutral stimulus, that never elicits the unconditional response by itself,
is introduced just before the presentation of the original stimulus.
[bell rings]
If the neutral or signaling stimulus is presented alone,
and a response occurs, as if the original stimulus were still there,
we say that conditioning has taken place.
[bell rings]
The arbitrary neutral stimulus becomes a conditioned stimulus.
[bell rings]
The reverse is also true.
Pavlov and others studied the extinction over time of such conditioned responses.
[bell rings]
When the subject learns that the conditioned stimulus no longer signals a desired event,
[bell rings]
the acquisition process is reversed as the learned connection is gradually weakened.
[bell rings continuously]
Pavlov's work, and the work of those who followed him, led to a remarkable conclusion,
and that is, any stimulus an organism can perceive
is capable of eliciting any reaction the organism is capable of making.
This means that virtually any sound, sight, or smell can influence the way our muscles tense or relax,
our moods fluctuate, or even the way our attitudes are formed.
For instance, if I say "Relax," and then do this,
[gun shot]
you're going to be startled and upset.
After five or six pairings of "relax", [gun shot]
just saying the word "relax"
is going to generate a negative response, rather than its usual learned reaction.