Transcript Introduction to Learning and Cognition

EFFECTS OF
REPEATED STIMULATION:
HABITUATION
HABITUATION
•LEARNING NOT TO RESPOND TO A PREVIOUSLY
MEANINGFUL STIMULUS
•THE STIMULUS USED TO PREDICT SOMETHING.
•NOW THE STIMULUS LOSES ITS
PREDICTABILITY AND YOU IGNORE IT
•ALLOWS EFFICIENCY IN LEARNING
HABITUATION
•LEARNING NOT TO RESPOND TO A PREVIOUSLY
MEANINGFUL STIMULUS
•THE STIMULUS USED TO PREDICT SOMETHING.
•NOW THE STIMULUS LOSES ITS
PREDICTABILITY AND YOU IGNORE IT
•ALLOWS EFFICIENCY IN LEARNING
HABITUATION
•LEARNING NOT TO RESPOND TO A PREVIOUSLY
MEANINGFUL STIMULUS
•THE STIMULUS USED TO PREDICT SOMETHING.
•NOW THE STIMULUS LOSES ITS
PREDICTABILITY AND YOU IGNORE IT
•ALLOWS EFFICIENCY IN LEARNING
HABITUATION
•LEARNING NOT TO RESPOND TO A PREVIOUSLY
MEANINGFUL STIMULUS
•THE STIMULUS USED TO PREDICT SOMETHING.
•NOW THE STIMULUS LOSES ITS
PREDICTABILITY AND YOU IGNORE IT
•ALLOWS EFFICIENCY IN LEARNING
HABITUATION
•LEARNING NOT TO RESPOND TO A PREVIOUSLY
MEANINGFUL STIMULUS
•THE STIMULUS USED TO PREDICT SOMETHING.
•NOW THE STIMULUS LOSES ITS
PREDICTABILITY AND YOU IGNORE IT
•ALLOWS EFFICIENCY IN LEARNING
DISHABITUATION
When the stimulus changes
Signals a change in the situation or setting
No longer appropriate to ignore, as changed stimulus may
have meaning
Why? Something has changed in environment
•
•
check to see if it is meaningful
react to new situation, adapt!
CHARACTERISTICS OF
HABITUATION
Response decrement: response strength decreases with
repeated stimulation.
Spontaneous recovery: if the stimulus is withheld and then represented, the organism will react to the stimulus
Repeated series: with repeated series of exposure, response
strength is less ad less
Generalization: similar stimuli may exhibit habituation when
presented
Dishabituation: what has been habituated can be dishabituated
Habituation and Dishabitation
Reaction measure
120
100
80
60
40
20
0
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Trials
EXAMPLES OF
HABITUATED BEHAVIOR
• Salivation responses
• Visual attention in human infants
• Startle response in rats
• Attention to your mother
• Reaction to fire alarms in college dorms!
SENSITIZATION
When aroused, even light stimuli elicit strong reactions
Are sensitized: opposite of habituation
• Over-react to stimuli
• Over vigilance or hypervigilance
When do we see this?
•
•
•
•
Overly hungry/thirst
Sexual behaviors
Aggression
Fear
WHY DO WE SHOW
HABITUATION AND SENSITIZATION?
It is adaptive!
Ignore what is irrelevant
Attend or hyper-attend to what is important
Is habituation and sensitization passive or active learning?
ISN’T THIS JUST FATIGUE OR
EXCITEMENT?
• Is habituation/sensitization the same or different from
sensory adaptation or response fatigue?
• Sensory Adaptation: occurs when you overstimulate a
sense system: overuse the receptors; must wait our
refractory period
• Response fatigue: the muscles are tired from responding
• How is learning to habituate or become sensitized
different than this?
EXAMPLE: VISITS TO
A NUDIST COLONY
•
when first get there- S (naked people) --> R (lots of blushing)
•
staring behavior decreases over your stay: repeated exposure
•
if leave and come back (repeated series) gets easier with each trip:
you adjust faster the more often you leave and come back
•
the more nude bodies- the easier to habituate: Frequency of
stimulation
•
might generalize: less embarrassed in locker room, etc.
•
some one comes in with a camera- suddenly embarrassed again dishabituation
OTHER EXAMPLES:
Solomon's research on dogs supports this:
• Dog presented with series of shocks
• with repeated presentations of shock, the dog's overt
behaviors and heart rate response was smaller
• however, the after reaction (decrease in heart rate at
cessation of shock) was greater
• it took longer for the heart rate to return to normal
OTHER EXAMPLES:
Visual attention in infants
• Depending on size/complexity of stimulus
• Infants showed simple habituation to simple visual stimuli
• But: when shown stimulus again, showed increased
sensitization (looked at it more)
Drug addiction: will talk about this with classical conditioning
Thrill seeking: go from frightened to adrenaline rush then
recovery
CONTEXT IS IMPORTANT
Depends on how/when/where stimulus is presented
• That is, reaction varies depending on context
Startle response:
• Sitting talking with friends
• Knowing that someone is about to jump out at you and
beating them to the “boo”
• Watching a scary movie
• A startle will produce different levels of reaction across these
settings
CONTEXT IS IMPORTANT
Touch and sexual responses are another good example
• Touch by a doctor
• Touch by your mom
• Touch by your lover
All can touch your face, ear, arm, etc., but it is context that
regulates how you react to it.
WHY HABITUATION
AND SENSITIZATION?
Adaptive: Learn what to attend to and ignore
Things are more exciting the first time they happen!
Can’t attend to everything: need to learn what the important
stimuli are
• Important stimuli change depending on context and
experience
• If don’t learn, die!
WHAT HAPPENS
PHYSIOLOGICALLY?
•
Simple Systems Approach: Eric Kandel
•
•
•
•
Look for similarities in process of habituation across species
See strong similarities in terms of behavior
Are physiological correlates also similar?
Why is this important?
•
•
If there are strong physiological AND behavioral similarities,
suggests that there are generalizable principles and
structures that underlie habituation
Suggests that this is a very basic and critical type of learning
•
•
If all organisms show it, must be very robust
Must be necessary for survival
THE SEA APLYSIA
• A large marine snail
• Contains only a few thousand neurons so can map
the neurons much more easily than larger animal
• Examine siphon or fleshy spout withdrawal
response
• When you poke the siphon, it withdraws into the
snail
• http://www.youtube.com/watch?v=wE54PPXgstM
GILL-WITHDRAWAL
REFLEX
• Siphon contains 24 sensory neurons that respond to
tactile stimulation
• 6 motor neurons control the gill-withdrawal response
• Each sensory neuron has a monosynptic connnection
• Direct connection that involves just one synapse
• Connects to EACH of the 6 motor neurons
• Axons from other sensory neurons involved in
polysynaptic connections
• indirect connections mediated by 1 or more interneurons
• Also connect to these motor neurons
HABITUATION OF THE
SIPHON
 Stimulate by touching once every minute for 10-15 trials
 Get habituation within this time
 Habituation lasts about 1 hour but can extend to 24 hours
 If continue this stimulation for 3-4 days: long term
habituation
 Lasts several weeks
 Change in way withdrawal reflex occurs
 Think of the parameters of habituation: what would you
expect?
WHAT IS HAPPENING
TO NEURONS?
•
During habituation: decrease in
excitatory conduction always occurs in
synapses involving the axons of the
sensory neurons
•
NO change in postsynaptic neuron’s
sensitivity to the neurotransmitter
•
What changed?
•
•
•
•
Amount of transmitter released by
presynaptic (sensory) neurons
With repeated stimulation: LESS
transmitter released into synapse
Similar process found in other
animals as well
Won Nobel prize for this work!
CHEMICAL MECHANISMS
IN HABITUATION?
• Each time a neuron fires, is an influx of calcium (Ca+) ions into
the axon terminals
• Calcium responsible for release of neurotransmitter
• Calcium current into axon terminals becomes progressively
weaker with repeated stimulation
WHY IMPORTANT?
• Physiological demonstration of learning
• Later work shows LTP and LTD of axons
• Able to pinpoint neural changes responsible for
habituation
• Habituation does not necessarily involve long term
anatomical changes, but temporary chemical changes
• Thus appears that learning is flexible:
• In short term, is likely due to chemical changes
• For more permanent memories: anatomical changes
EXPLANATION: OPPONENT
PROCESS THEORY
For every action there is a reaction (wait, isn’t that physics?)
Solomon and Corbitt (1974)
• lots of attention
• made very "broad"- tried to apply to everything
• Undermined their own theory
TWO (OKAY 4) EFFECTS
Primary affective reaction: initially excited by unexpected
event• get euphoria from this
• which will peak:
• E.g., Think have won the lottery
Adaptation phase and steady level: euphoria levels off
Peak of after-reaction: a let-down occurs- you were one
number off- get "depressed“
Decay of after reaction: return to baseline levels
CHURCH, ET AL., 1966
Dogs receive 10-s shock while restrained in harness
at first- many overt responses
•
•
•
freezing
escape behaviors
pain behaviors
at termination of shock: stealthy, hesitant, unfriendly behavior
after short time: friendliness reappeared heart rates paralleled
these changes
MODEL ASSUMES THAT:
For every hedonic reaction (state A) will come opposing reaction
(state B)
Decline in hedonic value from peak of state A to steady level will
result from state B's effect of reducing state A
Steady level of hedonic intensity is state A minus state B
When stimulus creating state A stops, full force of state B is felt
State B slowly decays until hedonic intensity turns to 0
TWO MAIN STATES
CRITICALLY DIFFER:
usually are opposite reactions
State A develops quickly, closely associated w/intensity of
stimulus that produces it
• when stimulus triggering state A is removed, state A ceases
state B develops slowly, produced as reaction to A
• is slow to decrease, when state A ceases, decays
EFFECTS OF REPEATED
STIMULATION
repeated presentation of stimulus eliciting state A habituation
occurs in state A
repeated elicitation of state B strengthens state B and reduces
intensity of state A
thus: REPEATED presentations of the stimulus that triggered
state A will actually lead to a reduction of state A --> because
state B increases in intensity
that is: w/extended experience:
•
•
the reaction to the initial stimulus will be smaller than before,
but the after reaction will be larger and of longer duration
CRITIQUE OF OPPONENT
PROCESS THEORY
Great deal of older research to support the basic phenomenon
common criticism: little actual evidence as to actual physiological
mechanisms that might correspond to hypothetical a and b states
various research shows vastly different time course between
examples: immediate to months long
CRITIQUE OF OPPONENT
PROCESS THEORY
Several Good aspects of theory
• as long as emotional responses conform to predictions of theory,
not matter whether these are based on single or multiple
physiological mechanisms
Theory is basically predictive
• good descriptive model, fairly well supported by research
greatest virtue may be its attempt to unite diverse emotional
situations into single framework
• allows for commonalities between emotional responses
HABITUATION AND
EATING
•
Eating involves repeated presentation of visual, olfactory,
gustatory and tactile cues
•
Habituation involves decreases in physiological and
behavioral responses to food
•
We eat in food bouts:
•
•
Begin a bout, often a brief increase in intake rate, followed by
a decreasing rate until cessation
Time between bouts can vary
•
•
•
Presence of other foods
Presence of other activities
Physiological states: physical and emotional/affective
HABITUATION AND
EATING
• What factors affect rate of habituation when eating?
• Dishabituation: presentation of another food increases
eating (but not necessarily for original food)
• Variety of foods at meal slows habituation
•
•
Different foods act as novel stimuli inbetween bites of
original food
Different foods slows habituation to one another
• Distractors: adding a distractor task slows habituation
LONG TERM
HABITUATION
• Often studied for startle, fear responses
• Think fire alarms:
• Repeated presentation with no cause
• Stop paying attention to fire alarm
• Generalizes to other settings
• VERY little research on LTH in humans or even other
animals
• Little evidence that it occurs for eating/food
AFFECTIVE/EMOTIONAL/
MOTIVATIONAL STATES
•
Classical conditioning is part of eating:
•
•
•
Comfort foods: foods associated with comfort
•
•
•
associate food with X
these are often “motivational” or affective/emotional states
Often from childhood
Eat to make us emotionally feel better
AESOP:
•
•
affective extension of standard operating procedure
assumption that classical conditioning links emotions and
food consumption