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•Conditioned reflex
activity of the organism.

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Pavlov and Classical Conditioning
• Ivan Pavlov was a physiologist who
won a Nobel Prize for his research on
digestion.
• His original description of classical
conditioning was a by-product of this
research. He did not set out to
discover classical conditioning.

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The classic experience of Pavlov is that of the dog, the bell
and the salivation to the view of a piece of meat. Whenever we
present to the dog a piece of meat, seeing and sniffing it and
makes the animal salivate. If we ring a bell, what is the effect
on the animal? An orienting reaction. It simply looks around
and turns its head to look for where that sound stimulus
comes from. If we repeatedly ring the bell, and immediately
after show the meat and give it to the dog, after a certain
number of times, simply ringing the bell provokes salivation
in the animal, preparing its digestive system to receive the
meat. The bell becomes a sign of the meat that will come later.
The whole body of the animal reacts as if the meat was
already present, with salivation, digestive secretions, digestive
motricity, etc. An stimulus that has nothing to do with
feeding, a mere sound, becomes then capable to induce
digestive modifications.

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Classical Conditioning
• Pavlov noticed that the dogs he used to do his
research salivated upon the sight of the lab
workers who fed them.
– He concluded that this reflex was
“psychological” because it was based on the
dog’s previous experiences.
– Further testing demonstrated that the sight of
food produced the same effect as giving the
same amount of food to the dog.

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• Pavlov started with the unconditioned reflex of
salivation to food. He hypothesized that this was
an automatic connection.
– The dogs had an unconditioned reflex between
food and secretion of digestive juices.
• A buzzer is called a neutral stimulus because it
elicits attention to the sound, but no automatic
connection.
– The dogs would lift their ears and look around
when the buzzer sounded, but no salivation
was produced

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• He conjectured that animals develop new
connections by transferring a response
from one stimulus to another.
– He hypothesized that if a buzzer always
preceded the food, the buzzer would
begin to elicit the reflex of salivation.
• After a few pairings of the buzzer with the
food, the dogs would begin to salivate as
soon as the buzzer sounded.

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• Terminology
–Unconditioned Stimulus (UCS) 
An event that consistently and
automatically elicits an
unconditioned response.
–Unconditioned Response (UCR) 
An action that the unconditioned
stimulus automatically elicits.

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• Terminology
– Conditioned Stimulus (CS)  Formerly
the neutral stimulus, having been paired
with the unconditioned stimulus, elicits
the same response. That response
depends upon its consistent pairing with
the UCR.
– Conditioned Response (CR)  The
response elicited by the conditioned
stimulus due to the training. Usually it
closely resembles the UCR.

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Classical conditioning: acquiring a new response (the
conditioned response) to a previously neutral stimulus (the
conditioned stimulus) that reliably signals the arrival of an
unconditioned stimulus.
Ivan Pavlov: Russian physiologist who initially was
studying digestion; first identified mechanisms of classical
conditioning
Also known as Pavlovian or Respondent Conditioning
Classical Conditioning

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Pavlov’s Experimental Setup

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Some Terms
• Reflex: a stimulus-response pair in which the stimulus
automatically elicits the response
• Unconditioned stimulus (UCS): the stimulus in a
reflex that automatically elicits a response
• Unconditioned response (UCR): the response in a
reflex that occurs automatically after the occurrence of
the unconditioned stimulus
• Example: physician strikes below knee with little
hammer (unconditioned stimulus)  knee jerk
(unconditioned response)

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Phases of classical conditioning: Classical conditioning
proceeds through
several phases, depending on the time of presentation of the two
stimuli.
If the conditioned stimulus regularly precedes the unconditioned
stimulus,
acquisition occurs. If the conditioned stimulus is presented by
itself, extinction
occurs. A pause after extinction yields a brief spontaneous
recovery.

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Reflex Action Conditional reflex Voluntary Action
(1) Inborn , instinctive Acquired via experience /
learning
Acquired via thinking /
reasoning
(2) Cerebrum not involved Cerebrum involved Cerebrum involved
(3) Involuntary &
unconscious
Voluntary & less conscious Voluntary & conscious
(4) Fast action Slow action Slow action
(5)Same stimulus same
response
Unrelated stimulus same
response
Same stimulus different
response

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Unconditioned stimulus: a stimulus that elicits a response
without training
Conditioned stimulus: A stimulus that elicits a response
because it has been repeatedly paired with an unconditioned
stimulus
Unconditioned response: An innate response elicited by an
unconditioned stimulus; usually either a reflex or an emotional
response
Conditioned response: Term used to refer to a reflex response
after learning has occurred to elicit the response by a
conditioned stimulus
Components of
Classical Conditioning

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There are two different stimuli:
• the unconditioned stimulus, which elicits the response
reflexively, without an training [the smell of food]
• the conditioned stimulus, which can only elicit the response
after training [the sound of the bell]
There is only one response [salivation]. What the response is
called depends on which stimulus elicited it:
• It is the unconditioned response when elicited by the
unconditioned stimulus [the smell of food]
• It is the conditioned response when elicited by the conditioned
stimulus [the sound of the bell]
More on Stimuli & Responses

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Stimulus Generalization: A tendency to respond to stimuli
that are similar, but not identical, to a conditioned stimulus
(e.g., responding to a buzzer or a hammer banging when the
conditioning stimulus was a bell)
Stimulus Discrimination: The ability to respond differently to
various stimuli (e.g., Rudy will respond differently to various
bells [alarms, school, timer])
Principles, continued

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Operant Conditioning: Learning based
on the consequences of responding; we
associate responses with their
consequences
Operant Reinforcer: Any event that
follows a response and changes its
likelihood of recurring
Operant Conditioning
(Instrumental Learning)

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Skinner Box
(conditioning chamber)
Apparatus
designed to study
operant
conditioning in
animals

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Operant reinforcement most effective when
given immediately after a correct response
Effectiveness of reinforcement is inversely
related to time elapsed after correct
response occurs
Timing of Reinforcement

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The training of dolphins by rewarding them with food is
an example of positive reinforcement operant
conditioning.

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Types of Conditioning
consequence:
desirable
(appetitive)
undesirable
(aversive)
given positive reinforcement positive punishment
taken away negative punishment negative reinforcement
yellow increases behavior; blue decreases behavior

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Comparison: Classical & Operant
Conditioning

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Comparison: Classical & Operant
Conditioning, 2
classical operant
behavior involuntary (reflexive) voluntary (nonreflexive)
association of events (CS & UCS) of response & reinforcer
expectation
that CS signals arrival of
UCS
that behavior will be
reinforced

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Primary Reinforcer: Unlearned and natural; satisfies
biological needs (e.g., food, water, sex)
Secondary Reinforcer: Learned reinforcer (e.g.,
money, grades, approval, praise)
Token Reinforcer: Tangible secondary reinforcer
(e.g., money, gold stars, poker chips)
Social Reinforcer: Provided by other people (e.g.,
learned desires for attention and approval)
Types of Reinforcers

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Continuous Reinforcement: A reinforcer
follows every correct response
Partial Reinforcement: Reinforcers do NOT
follow every response
Partial Reinforcement Effect: Responses
acquired with partial reinforcement are very
resistant to extinction
Continuous & Partial
Reinforcement

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Review: Types of Reinforcers

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Synaptic theory of creation
conditioned reflex

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ECG recording in sleep

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ECG stages of sleep

40. THE END!