Pavlovs Discovery

Classical Conditioning: Learning Signals and Associations
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Learning is a relatively permanent change in behavior or knowledge due to experience. We are born with some behaviors and knowledge, we acquire others automatically
as we grow (through maturation), and we learn still others. Some of our sayings, such as
“Once burned, twice shy” and “Fool me once, shame on you; fool me twice, shame on
me,” reflect this vital learning process. In fact, learning plays a central role in most aspects
of human behavior. If you want to know who you are and how you became the person
you are today, examining what and how you have learned is a good place to start.
This chapter describes what psychologists now know about the fundamental principles of learning. These include a form of learning called operant conditioning, in which
rewards and punishments affect the frequency of observable behavior. There is also classical conditioning, a form of learning in which specific signals come to trigger behavior. In addition, there are cognitive processes that underlie some of the most complex
forms of learning, such as the ability to learn from watching others. Some learning takes
place consciously, as when you study for an exam; but as mentioned later, you can also
learn things without being aware that you are doing so (Watanabe, Náñez, & Sasaki,
2001). Let’s begin by considering classical conditioning.
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Tutorial: Classical
Conditioning—
Pavlov’s Study
Classical Conditioning: Learning
Signals and Associations
䉴 How did Russian dogs teach psychologists about learning?
At the first notes of the national anthem, an athlete’s heart may start to pound, because
those sounds signal that the game is about to begin. A flashing red light on the instrument panel might raise your heart rate, too, because it means that something is wrong
with your car. People are not born with these reactions. They have learned them by
observing relationships, or associations, between events in the world. The experimental
study of this kind of learning was begun, almost by accident, by Ivan Petrovich Pavlov.
Pavlov’s Discovery
learning The modification of preexisting behavior and understanding.
Pavlov is one of the best-known figures in psychology, but he was not a psychologist.
He was a Russian physiologist who won the Nobel Prize in 1904 for his research on the
digestive system of dogs. In the course of this research, Pavlov noticed a strange phenomenon. His dogs sometimes salivated, or drooled, when no food was present. For
instance, they salivated when they saw the assistant who normally brought their food,
even if he was empty-handed.
Pavlov devised a simple experiment to determine why salivation occurred without
an obvious physical cause, such as food. First he performed an operation to divert a
dog’s saliva into a container so that the amount of salivation could be measured. Next
he placed the dog in an apparatus similar to the one shown in Figure 5.1. The experiment had three phases.
In the first phase, Pavlov and his associates confirmed that when meat powder was
placed in the dog’s mouth, the dog automatically salivated (Anrep, 1920). They also
confirmed that the dog did not automatically salivate in response to a musical tone.
The researchers had now established the two basic components of Pavlov’s experiment:
(1) a quick, automatic response called a reflex and (2) a neutral stimulus that does not
trigger that reflex.
In the second phase of Pavlov’s experiment, the tone was sounded, and then meat
powder was placed in the dog’s mouth. The dog salivated. This pairing of the tone and
the meat powder was repeated several times. So the tone always preceded the arrival of
the meat powder, but had the dog learned that relationship? It had. In the third phase
of the experiment, the tone was sounded, but no meat powder was presented. Even so,
the dog still salivated. The tone alone was now enough to trigger salivation. You may
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Chapter 5
Learning
FIGURE 5 .1
Apparatus for Measuring
Conditioned Responses
In this more elaborate version of Pavlov’s
original apparatus, the amount of saliva
flowing from a dog’s mouth is measured
precisely and then recorded on a slowly
revolving drum of paper.
Pen recording
on cylinder
have seen a similar process if you regularly open pet food with an electric can opener.
The sound of the opener probably brings your pet running (and salivating) because
that sound means that food is on its way.
Pavlov’s experiment demonstrated what we now call classical conditioning. In this
procedure, a neutral stimulus is repeatedly paired with a stimulus that already triggers
an automatic, reflexive response. As a result of this pairing, the previously neutral stimulus itself comes to trigger a response that is similar to that reflex. Figure 5.2 shows the
basic elements of classical conditioning. The stimulus that naturally elicits a response
without conditioning, such as the meat powder in Pavlov’s experiment, is called
the unconditioned stimulus (UCS). The automatic, unlearned, reflexive response to this
stimulus is called the unconditioned response (UCR). After being paired with the
unconditioned stimulus (meat powder), the previously neutral stimulus becomes
the conditioned stimulus (CS), and the response it comes to trigger is a learned or
conditioned response (CR).
FIGURE
5.2
Classical Conditioning
Before classical conditioning has occurred,
meat powder on a dog’s tongue produces
salivation, but the sound of a tone—a
neutral stimulus—brings only orienting responses such as turning toward the sound.
During the process of conditioning, the
tone is repeatedly paired with the meat
powder. After classical conditioning has
taken place, the sound of the tone alone
acts as a conditioned stimulus, producing
salivation.
PHASE 1: Before conditioning has occurred
UCS
(meat powder)
UCR
(salivation)
Neutral stimulus
(tone)
Orienting
response
PHASE 2: The process of conditioning
Neutral stimulus
(tone)
followed
by
UCS
(meat powder)
UCR
(salivation)
PHASE 3: After conditioning has occurred
CS
(tone)
CR
(salivation)