Psychology 2250
Last class
Definition of learning
Distinction between learning and performance
Habituation and Sensitization
Dual-Process Theory
S-R system
State system
Habituation and Sensitization
Characteristics of Habituation and Sensitization
Time course
Sensitization is usually temporary
-sensitization can last for up to a week but not
generally a long-term effect.
-with a stronger stimulus, the effects last longer.
Habituation can be short-term or long-term, depending on
presentation and interval between stimuli.
Short-term habituation:
-rapid presentations of a stimulus with a short interval
between presentations
-results in habituation quickly but see spontaneous
recovery
-the degree of spontaneous recovery depends on length
of rest interval.
Long-term habituation:
-one stimulus presentation a day
-see more long-term effects
-see less spontaneous recovery
Tones Once a Day
Tones
Tones Every 3
seconds on 1 day
Blocks of 30 Tones
Leaton, 1976; see page 46 of Domjan
Tones Once a
Day
Tones
Stimulus specificity
Habituation is stimulus-specific
-if you change the stimulus, see recovery of the
response
Sensitization is not highly stimulus-specific
-if an animal is aroused, it is usually aroused to a
variety of cues
Effects of strong extraneous stimuli
If you change the nature of the eliciting stimulus you see
recovery of the habituated response.
Can also see recovery of the response if the animal is given
a rest period = spontaneous recovery.
The response can also be restored by presenting a strong
stimulus— this is called dishabituation.
Dishabituation refers to recovery of the response to the
habituated stimulus following presentation of a different,
novel stimulus.
Habituation and Sensitization in Aplysia
Habituation of the gill withdrawal reflex results from
changes in the S-R pathway
Less transmitter
released here
Skin
SN
MN
Gill
Dishabituation/Sensitization
After the gill withdrawal reflex has habituated, a shock to
the tail sensitizes the gill withdrawal reflex elicited by
touching either the mantle or siphon
Dishabituation is a case of Sensitization
Sensitization (dishabituation) occurs because tailshock
augments the release of neurotransmitter from the
sensory neuron
Tail
Skin
SN
FN
MN
Gill
The Opponent-Process Theory of
Motivation
(Solomon and Corbit, 1974)
The concepts of habituation and sensitization have
been extended to emotions and motivated behavior
Common characteristics of emotional reactions
1. Emotional reactions are biphasic; a primary reaction is
followed by an opposite after-reaction
2. The primary reaction becomes weaker with repeated
stimulations
3. The after-reaction is strengthened
The Opponent-Process Theory is a homeostatic theory
The theory assumes that neurophysiological mechanisms
involved in emotional behavior serve to maintain emotional
stability
Drug-seeking behavior
a-b
Observed
Response
Underlying
Opponent
Processes (a
and b)
a
Observed
So primary
emotion is less affective afterreaction is greater
a-b
a
a process: same
b
b
Stimulus
Presentation
Time
First Presentation
of Arousing S
After Many
Presentations of
Arousing S
b process:
Starts earlier
Lasts longer
Is larger
Classical Conditioning
or Pavlovian conditioning
Ivan P. Pavlov
 was a Russian physiologist who accidentally discovered this
type of learning
he was studying the physiology of digestion when he noticed
a funny thing.
digestion starts in the mouth where saliva begins to break
down food. Dogs would salivate when he put the food powder
in their mouths.
But experienced dogs would also salivate when the experimenter
walked in the room or at the sight of food.
An apparatus for Pavlovian conditioning. A tube carries saliva from the dog’s
mouth to a lever that activates a recording device (far left). During conditioning,
various stimuli can be paired with a dish of food placed in front of the dog.
The device pictured here is more elaborate than the one Pavlov used in his early experiments.
Pavlov paired the clicking of a metronome with food.
Clicker
Food (never used a bell)
Dogs normally salivate with food but not with the clicker
After a few of these pairings, dogs began to salivate when the
metronome came on.
The first stimulus (clicker) triggered the memory
(or anticipation) of the second stimulus (food).
Thus, we can say the 2 events have become associated.
Association: If 2 sensations, or stimuli, repeatedly occur
together, the mental reactions to those stimuli become
associated such that when the first sensation or stimulus is
given, it triggers the memory of the associated stimulus.
Those of you with pets will have already seen this
phenomenon in action.
Formal definition of Pavlovian conditioning
2 stimuli occur together regardless of the subjects’
behavior
in Pavlov’s original experiment, food was given
even if the dogs didn’t salivate to the clicker.
In this type of conditioning we set up conditions,
or pairings, beforehand and present them regardless
of the subject’s behavior.
Decide on clicker
food pairings and then present
them a # of times regardless of what the animal does to
the clicker.
Four major terms apply to Pavlovian Conditioning experiments
Stimuli
US
Unconditioned stimulus
Biologically potent stimulus that
reliably evokes an unlearned or
reflexive reaction (i.e., food)
CS
Conditioned stimulus
Biologically weak stimulus
The CS may evoke an orienting
response, but not the strong
response evoked by the US
(i.e., metronome)
Responses
UR
Unconditioned response
The unlearned response
triggered by the US
Powerful and reflexive
(i.e., salivation to food)
CR
Conditioned response
It is elicited by the CS and
represents the learned behavior
The behavioral manifestation of the
underlying association between the
CS and the US
(i.e., salivation to the Metronome)
Pavlov’s original experiment is an example of Excitatory
classical conditioning.
Excitatory means the CS is able to excite the CR into being.
From a procedural point of view, conditioned excitation,
or excitatory conditioning occurs when presentation of the
CS is followed by a presentation of the US
(i.e., CS
US pairings).
Two types of Excitatory Conditioning
Appetitive
CS is followed by an
appetitive (good) US
(i.e., food, water, mate)
Aversive
CS is followed by an
aversive US
(i.e., mild shock, illness)