2HabituationLearning not to respond to a previously meaningful stimulusThe stimulus used to predict something.Now the stimulus loses its predictability and you ignore itAllows efficiency in learning
3HabituationLearning not to respond to a previously meaningful stimulusThe stimulus used to predict something.Now the stimulus loses its predictability and you ignore itAllows efficiency in learning
4HabituationLearning not to respond to a previously meaningful stimulusThe stimulus used to predict something.Now the stimulus loses its predictability and you ignore itAllows efficiency in learning
5HabituationLearning not to respond to a previously meaningful stimulusThe stimulus used to predict something.Now the stimulus loses its predictability and you ignore itAllows efficiency in learning
6HabituationLearning not to respond to a previously meaningful stimulusThe stimulus used to predict something.Now the stimulus loses its predictability and you ignore itAllows efficiency in learning
7Dishabituation When the stimulus changes Signals a change in the situation or settingNo longer appropriate to ignore, as changed stimulus may have meaningWhy? Something has changed in environmentcheck to see if it is meaningfulreact to new situation, adapt!
8Characteristics of habituation Response decrement: response strength decreases with repeated stimulation. Spontaneous recovery: if the stimulus is withheld and then re- presented, 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
10Examples of habituated behavior Salivation responsesVisual attention in human infantsStartle response in ratsAttention to your motherReaction to fire alarms in college dorms!
11Sensitization When aroused, even light stimuli elicit strong reactions Are sensitized: opposite of habituationOver-react to stimuliOver vigilance or hypervigilanceWhen do we see this?Overly hungry/thirstSexual behaviorsAggressionFear
12WHY 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?
13Isn’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 periodResponse fatigue: the muscles are tired from respondingHow is learning to habituate or become sensitized different than this?
14Example: Visits to a Nudist Colony when first get there- S (naked people) --> R (lots of blushing)staring behavior decreases over your stay: repeated exposureif leave and come back (repeated series) gets easier with each trip: you adjust faster the more often you leave and come backthe more nude bodies- the easier to habituate: Frequency of stimulationmight generalize: less embarrassed in locker room, etc.some one comes in with a camera- suddenly embarrassed again - dishabituation
15Other Examples: Solomon's research on dogs supports this: Dog presented with series of shockswith repeated presentations of shock, the dog's overt behaviors and heart rate response was smallerhowever, the after reaction (decrease in heart rate at cessation of shock) was greaterit took longer for the heart rate to return to normal
16Other Examples: Visual attention in infants Depending on size/complexity of stimulusInfants showed simple habituation to simple visual stimuliBut: when shown stimulus again, showed increased sensitization (looked at it more)Drug addiction: will talk about this with classical conditioningThrill seeking: go from frightened to adrenaline rush then recovery
17Context is important Depends on how/when/where stimulus is presented That is, reaction varies depending on contextStartle response:Sitting talking with friendsKnowing that someone is about to jump out at you and beating them to the “boo”Watching a scary movieA startle will produce different levels of reaction across these settings
18Context is importantTouch and sexual responses are another good exampleTouch by a doctorTouch by your momTouch by your loverAll can touch your face, ear, arm, etc., but it is context that regulates how you react to it.
19Why habituation and sensitization? Adaptive: Learn what to attend to and ignoreThings are more exciting the first time they happen!Can’t attend to everything: need to learn what the important stimuli areImportant stimuli change depending on context and experienceIf don’t learn, die!
20What happens physiologicallY? Simple Systems Approach: Eric KandelLook for similarities in process of habituation across speciesSee strong similarities in terms of behaviorAre 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 habituationSuggests that this is a very basic and critical type of learningIf all organisms show it, must be very robustMust be necessary for survival
21The Sea Aplysia A large marine snail Contains only a few thousand neurons so can map the neurons much more easily than larger animalExamine siphon or fleshy spout withdrawal responseWhen you poke the siphon, it withdraws into the snail
22Gill-withdrawal reflex Siphon contains 24 sensory neurons that respond to tactile stimulation6 motor neurons control the gill-withdrawal responseEach sensory neuron has a monosynptic connnectionDirect connection that involves just one synapseConnects to EACH of the 6 motor neuronsAxons from other sensory neurons involved in polysynaptic connectionsindirect connections mediated by 1 or more interneuronsAlso connect to these motor neurons
23Habituation of the Siphon Stimulate by touching once every minute for trialsGet habituation within this timeHabituation lasts about 1 hour but can extend to 24 hoursIf continue this stimulation for 3-4 days: long term habituationLasts several weeksChange in way withdrawal reflex occursThink of the parameters of habituation: what would you expect?
25What is happening to neurons? During habituation: decrease in excitatory conduction always occurs in synapses involving the axons of the sensory neuronsNO change in postsynaptic neuron’s sensitivity to the neurotransmitterWhat changed?Amount of transmitter released by presynaptic (sensory) neuronsWith repeated stimulation: LESS transmitter released into synapseSimilar process found in other animals as wellWon Nobel prize for this work!
26chemical mechanisms in Habituation? Each time a neuron fires, is an influx of calcium (Ca+) ions into the axon terminalsCalcium responsible for release of neurotransmitterCalcium current into axon terminals becomes progressively weaker with repeated stimulation
27Why important? Physiological demonstration of learning Later work shows LTP and LTD of axonsAble to pinpoint neural changes responsible for habituationHabituation does not necessarily involve long term anatomical changes, but temporary chemical changesThus appears that learning is flexible:In short term, is likely due to chemical changesFor more permanent memories: anatomical changes
28Explanation: Opponent Process Theory For every action there is a reaction (wait, isn’t that physics?)Solomon and Corbitt (1974)lots of attentionmade very "broad"- tried to apply to everythingUndermined their own theory
29Two (okay 4) effectsPrimary affective reaction: initially excited by unexpected event-get euphoria from thiswhich will peak:E.g., Think have won the lotteryAdaptation phase and steady level: euphoria levels offPeak of after-reaction: a let-down occurs- you were one number off- get "depressed“Decay of after reaction: return to baseline levels
30Church, et al., 1966Dogs receive 10-s shock while restrained in harnessat first- many overt responsesfreezingescape behaviorspain behaviorsat termination of shock: stealthy, hesitant, unfriendly behaviorafter short time: friendliness reappeared heart rates paralleled these changes
31Model 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
32Two main states critically differ: usually are opposite reactionsState A develops quickly, closely associated w/intensity of stimulus that produces itwhen stimulus triggering state A is removed, state A ceasesstate B develops slowly, produced as reaction to Ais slow to decrease, when state A ceases, decays
33Effects of Repeated Stimulation repeated presentation of stimulus eliciting state A habituation occurs in state Arepeated elicitation of state B strengthens state B and reduces intensity of state Athus: REPEATED presentations of the stimulus that triggered state A will actually lead to a reduction of state A --> because state B increases in intensitythat 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
35Critique 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
36Critique of Opponent Process Theory Several Good aspects of theoryas long as emotional responses conform to predictions of theory, not matter whether these are based on single or multiple physiological mechanismsTheory is basically predictivegood descriptive model, fairly well supported by researchgreatest virtue may be its attempt to unite diverse emotional situations into single frameworkallows for commonalities between emotional responses
37Habituation and eating Eating involves repeated presentation of visual, olfactory, gustatory and tactile cuesHabituation involves decreases in physiological and behavioral responses to foodWe eat in food bouts:Begin a bout, often a brief increase in intake rate, followed by a decreasing rate until cessationTime between bouts can varyPresence of other foodsPresence of other activitiesPhysiological states: physical and emotional/affective
38Habituation 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 habituationDifferent foods act as novel stimuli inbetween bites of original foodDifferent foods slows habituation to one anotherDistractors: adding a distractor task slows habituation
39Long term habituation Often studied for startle, fear responses Think fire alarms:Repeated presentation with no causeStop paying attention to fire alarmGeneralizes to other settingsVERY little research on LTH in humans or even other animalsLittle evidence that it occurs for eating/food
40Affective/emotional/motivational states Classical conditioning is part of eating:associate food with Xthese are often “motivational” or affective/emotional statesComfort foods: foods associated with comfortOften from childhoodEat to make us emotionally feel betterAESOP:affective extension of standard operating procedureassumption that classical conditioning links emotions and food consumption
41Habituation and eating! Taking what we know about habituation and applying to food intake (especially in humans).Eat a single food in a meal = faster habituationDistractions reduce rate of habituationReadingWatching tvtalkingDishabituation occurs during meals:eatIng another food affects habituation for each foodShould we eat 1 food or many foods at a meal?What is the effect of drinking/beverages?In animals: eating bouts followed by drinking boutsSame in humansDoes drinking = dishabituation?Does drinking = disruption of eating?Why do bars give out free popcorn and restaurants bring drinks before ordering?
42Memory and eating Memory for food is important Do we like this food? Is it familiar? It is rich? Etc….Differences in individuals for memory for any given foodAlso individual differences in memory for intake of foodParticularly normal body weight and obeseAnorexics, bulimic individuals show differences from typical body weight individualsImportant factor is sensitization:Food tastes better to somePhysical differences: more or fewer taste budsBodily statesPersonal experiences
43Memory and eating Learning is important part of this memory Clean plate club or not?Individual differences again:Highly sensitized individuals more prone to overeating?Differences in processing of stimulus signalsIs over-eating an addiction?Differences in way we react to foodDifferences in size of DA spike for foods across individualsSome people may be physiologically primed to become “addicted”
44Isn’t overeating just sensory specific satiety? Authors argue that eating is more than simple satietySatiety = full; stop eating because you have had enoughHabituation = stop eating because you are “tired of the food”Two are not necessarily related!Habituation model assumes:Hedonic value of one food may influence hedonic value of another foodAllows for dishabituation, distraction effectsAssumes habituation is a normal nervous system processesSensory specific satiety only deals with eating and food, not other kinds of stimuliHabituation model assumes that LEARNING is critical factorAll the associative stimuli influence intakeWe eat long after it “tastes good”
45Implications of habituation model of eating: We must examine individual differences inDopaminergic/reward systemsBehavioral histories with foodEmotional/affective statesUnlike in animals, eating for most humans is NOT an energy intake regulation behavior, but a learned behaviorWe eat because we areHungryBoredUpsetReplacing a thwarted activityIt feels good
46Good eating practices? Present low fat/healthy food in variety Lots of different kinds of these foods presented at onceEncourage low rates of habituationEven encourage disruptorsPresent high fat/unhealthy food aloneEat alone in absence of disruptionsAllow for faster habituation of that foodBut: don’t assume long term habituation!