Transcript The Modification of Instinctive Behavior

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THE MODIFICATION OF
INSTINCTIVE BEHAVIOR
Elicited or Unconditioned Behavior
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

Occurs without past experience
Modifiable with experience (examples: habituation
and sensitization
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Some Types of Elicited Behaviour
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

An eliciting or unconditioned stimulus elicits a
response without any prior learning
Types of Elicited Behaviour
 Simple
Reflex
 Orienting Reflex
 Taxis (taxes)
 Kinesis (kineses)
 Fixed/Modal Action Patterns
FAPs/MAPs
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Sequence of behaviors directed at the eliciting (sign
or releasing) stimulus
Sometimes requires underlying drive
(hydraulic/energy model)
Vigor of response depends on how closely the sign
stimulus corresponds to the ideal stimulus (e.g., cute
baby)

Small (non-ideal), Normal (ideal), Supernormal (exaggerated
ideal)
Releasing Stimuli
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Supernormal stimulus
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An accurate 3-dimensional model of a herring gull's
head (a), and a 'supernormal' bill (b).
Supernormal stimulus
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Supernormal stimulus?
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versus
1950s
1990s
Lorenz – Tinbergen Model
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Energy Model
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
Action-specific energy: an internal force that
motivates a specific action
 Builds
up “internal pressure” that motivates animal to
behave in a certain way
 IRM

(innate releasing mechanism) releases stored
energy
Appetitive behavior: instinctive or learned response
motivated by action-specific energy and attracted
to a sign stimulus
Environmental Release
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Sign stimuli are environmental stimuli
Some are simple
 Others are quite complex


Likelihood of eliciting a FAP depends on
Accumulated level of action-specific energy
 Intensity of the sign stimulus


The relationship is inverse

The greater the level of accumulated energy, the weaker
the sign stimulus that can release the FAP
Conflicting Motives
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When two incompatible sign stimuli are
encountered, the response may be different from
the FAP from either acting alone
A
third instinct system, different from either of the two
conflicting systems, is activated

Displacement: in a conflict situation, the occurrence
of a behavior unrelated to that conflict
Habituation
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


a simple type of learning which is shown by a
change in elicited behaviour over trials
defined as a reduction in responsiveness (frequency,
magnitude) over successive trials
sometimes short-lasting and sometimes long lasting
Habituation-One Type of Modifiability
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Eric Kandel and Aplysia
Kandel`s Experiments
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Touch
Siphon
Gill
Withdrawal
Habituation
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gill withdrawal
touch
Forms of Habituation
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
Short-Term
 lasts
only a few minutes
 best if stimulus applied at short intervals (2-s)
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Long-Term
 lasts
weeks
 best if stimulus applied at longer intervals (30-s)
Simplified Circuit
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Mechanism of Short-term?
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decreases in
synaptic transmission
loss of skin
sensitivity
decrease in motor
synapse
fatigue
Not Muscle Fatigue
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Spontaneous
Evoked
Pinsker et al., (1970) Science 167:1740
Mechanism of Short-term?
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decreases in
synaptic transmission
loss of skin
sensitivity
decrease in motor
synapse
fatigue
Not Motor Synapse
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Before
skin
SN
After
electrical
MN
record
gill
Kupfermann et al., (1970) Science 167:1743
Mechanism of Short-term?
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decreases in
synaptic transmission
loss of skin
sensitivity
decrease in motor
synapse
fatigue
Skin Sensitivity?
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touch
skin
SN
MN
record MN
activity to assay
habituation
Trials 1 to 8
gill
Kupfermann et al., (1970) Science 167:1743
Not Skin Sensitivity
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touch
skin
SN
block
MN
record MN
activity to assay
habituation
Trials 10 -20
gill
Kupfermann et al., (1970) Science 167:1743
What’s the Mechanism of Short-term?
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decreases in
synaptic transmission
loss of skin
sensitivity
decrease in motor
synapse
fatigue
Mechanism:Short-term Habituation
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Decrease in neurotransmitter
released at the synapse with
both the motor neuron and the
interneuron!
Mechanism of Long-Term Habituation
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Change in the number of synapses!
Properties of Habituated Responses
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1. Spontaneous Recovery
2. Dishabituation
3. Generalization
Spontaneous Recovery
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Hi
Response
Stimulus
Time
Passes
Lo
Number of Presentations
Dishabituation
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Hi
Response
Stimulus
Novel
Event
(no time
passes)
Dishabituation
Lo
Number of Presentations
Generalization
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Sensitization- Another Type of
Modifiability

enhanced response to a “benign” stimulus after exposure to a
“noxious” one (most common)


for example, startle
enhanced response after repeated presentations of a “not so
benign” stimulus (less common)
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Rat
Startle
Human Startle
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Thompson/Groves Dual Process Theory
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Competition between two separate processes
1. S-R System: Habituation
2. State System: Sensitization
Conditions Favouring Habituation
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1.
2.
3.
4.
5.
6.
7.
Calm organism
Shorter interstimulus intervals
Less variable interstimulus intervals
Low intensity
Less complexity
More trials
More Stimulus Specificity
Interstimulus Interval
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Complexity
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Looking
Time
Trials
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One example of habituation is when animals
gradually eat more of a novel food after initial
ingestional neophobia
 Ingestional
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neophobia: the avoidance of novel foods
Habituation of the neophobic response can lead to
increased consumption of novel foods
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Animals can also show an increased neophobic
response
 If
an animal is ill when it ingests a novel food, it may
avoid the food in the future
 The greater neophobic response when animals are ill is
due to sensitization process
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Experience can also influence the properties of a
reward
Homeostasis has traditionally been considered
responsible for either increased or decreased
effectiveness of a reward
 Decreased
effectiveness due to satiation
 Increased effectiveness due to deprivation
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However, it appears that habituation and
sensitization can also influence
 Habituation
leads to decreased effectiveness
 Sensitization leads to increased effectiveness
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Habituation and sensitization can explain changes in
reward effectiveness that cannot be explained by
homeostasis
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Habituation is the process that filters out external
stimuli of little relevance by raising the sensory
threshold to those stimuli
Sensitization decreases sensory thresholds to
potentially relevant external events
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Thus, habituation and sensitization are processes
that optimize an animal’s likelihood of detecting
significant external events
The Dishabituation Process
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Dual process theory states that the arousing effect
of the sensitizing stimulus causes the habituated
response to return
In the absence of the sensitizing stimulus, habituation
remains
The Nature of Dishabituation
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
Pavlov suggested that dishabituation is a reversal
of habituation
 Thus,
the dishabituation of the withdrawal response in
Aplysia would be a return to the pre-habituation level
of neurotransmitter released from the sensory neuron
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In contrast, Grether proposed that dishabituation
results from a process similar to sensitization
superimposed on habituation
 In
Aplysia, this would suggest two processes
 Decreased
neurotransmitter release as a result of
habituation
 Increased neurotransmitter release produced as a result of a
sensitization experience
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Most research supports Grether’s view
Habituation and sensitization are simultaneously
independent and interdependent processes
The interdependence of habituation and sensitization
has adaptive value
Habituation allows us to ignore unimportant stimuli
 Sensitization reinstates the response in case those stimuli now
have become important

Opponent-Process Theory
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Opponent process theory: the theory that an event
produces an initial instinctive affective response,
which is followed by an opposite affective response
Our Initial Reaction
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All experiences, both biological and
psychological, produce an initial affective
reaction
A
state: the initial affective reaction to an
environmental stimulus in opponent process theory
 The strength of the A state is influenced by the
intensity of the experience
 The
more intense, the stronger the A state
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The A state arouses a second affective reaction
B
state: the opposite affective response that is elicited
by the initial affective reaction in opponent process
theory
 The B state is opposite the A state
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Initially, the B state is less intense than the A state
The B state also intensifies more slowly than the A
state
After an event has terminated, the B state
diminishes more slowly than the A state
The opponent affective response will be
experienced only when the event ends
Intensification of the Opponent B State
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Repeated experience with a certain event often
increases the strength of the opponent B state
This reduces the magnitude of the affective reaction
experienced during the event
 Thus,
the strengthening of the opponent B state may
well be responsible for the development of tolerance
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Tolerance: reduced reactivity to an event with
repeated experience
When the event ends, an intense opponent affective
response is experienced
 Withdrawal:
an increase in the intensity of the effective
opponent B state following the termination of an event
The Addictive Process
The Addictive Process
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Opponent process theory offers an explanation for
the development of addiction
Addictive behavior is a coping response to an
aversive opponent B state
Addictive behavior is an example of behavior
motivated to terminate (or prevent) the unpleasant
withdrawal state
Parachute jumpers – create a B state in order to feel
the A state.