Chapter 2: Habituation & Other Forms of Stimulus Learning
PSY 445: Learning & Memory
The act of attending to novel or unexpected stimuli “Investigative reflex”
Composite of several possible physiological and behavioral reactions Startle response
▪ Several different body movements may be involved here
Sense receptors are activated ▪ This orienting of receptors has evolutionary
basis▪ Defensive behaviors are primed
Increase in arousal ▪ Physiological▪ Psychological
Affected by:Stimulus intensityExpectancyRelevancePotential for danger
Q: Is OR learning?A: No--there is no permanent change in
behavior or knowledge. The OR is an innate response.
A decrease in the magnitude of the OR as a result of repeated stimulationOrganisms decrease responding to a stimulus after repeated exposuresA simple form of learning in which the organism learns something about a single stimulusCommon examples:
Noises in your houseTrafficAir conditioning/furnace
Most pervasive form of learningHas received little attention compared to more complex forms of learningOversight may have resulted from belief that habituation is not “real” learningMany theorists believe that learning only occurs in situations where connections are formed between two or more events: “associative learning”
Habituation is considered by most to be a learned decrease in responding to repeated stimulationHowever, there are some alternative explanationsWe will discuss these later
Whole-Body Startle ReactionReaction to loud sounds is studied using laboratory animalsIn rats, we can measure startle in a stabilimeter chamberRat jumps, chamber bounces and sensors detect the amount of movement
Skin Conductance ResponseElectrodes placed on bodies of humans
Siddle, Kuiack, & Kroese (1983)
Eye Fixations to Novel StimuliMeasurement of change in duration or number of eye fixationsNovelty Recognition TaskNew objects added to test environment; active exploration indicates orienting
Thompson & Spencer (1966)Parametric: taking one dimension of an independent variable and systematically varying it to map out the changes that occurThese researchers derived several parametric features of habituationSee next few slides
Number of repetitions of a stimulusExact number required for OR decrement varies considerablyAnywhere from one, to hundreds of presentations
If stimulus is not presented for a period of time, the OR tends to spontaneously recoverIf the delay interval is sufficiently long, the OR may recover completely
Habituation occurs more quickly on each successive occasion
Savings EffectAmount of recovery of the OR is less after each delay interval
The shorter the interval between stimulus presentations, the more quickly responding decreases
Gatchel (1975)One group tone presented every 20 seconds; another group every 100 secondsBy last 15 presentations, 20 second group had less responses to the tone
Massed Practice: more habituation in the short run
Spaced Practice: habituation lasts longer - less spontaneous recovery
Habituation to a stimulus can be temporarily blocked by a novel stimulusThe novel stimulus increases the OR to the original stimulus when the original is re-presented
Siddle (1985)Participants receive 15 presentations of 4-second tone
OR decreases to almost nothing as the result of habituation
New stimulus (patch of red light) is presented New OR specific to light occurs
Tone is then presented again (16th time overall) OR increases as compared to 15th
presentation; dishabituation has taken placePresenting the tone again will lead to the reappearance of habituation; OR returns to previous low level
Habituation may spread to similar stimuliThe more similar the stimuli, the greater the degree of generalization
Nonlearning Explanations Dual Process Theory Aplysia: A Model System Cognitive Theories
Habituation is due to sensory adaptation Sense receptors simply become less sensitive
with repeated stimulus presentationNot a decrease in motor responsivity:
but it is simply fatigue Response system has become depleted; we
become too tired to respond Recovery after rest does not prove that
response decrement was learned
Very questionable explanationsSeems that if you change the stimulus, an increase in responding will occur
See study by Siddle, Kuiack, & Kroese (1983) (mentioned earlier) as evidence of this
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 (dishabituation)
Repeated stimulation of Spinal-Reflex (S-R) pathway leads to a decline in ability of stimulus to evoke response: habituation
However, it also leads to activation of the state system, increasing the general tendency to respond: sensitization Two competing tendencies are occurring
SensitizationAn increase in the magnitude of the OR as a result of repeated stimulationTypically occurs only with very intense stimuli accompanied by physiological arousalMultiple experiences to a stimulus may enhance responding
Q: Is sensitization learning?A: No.
Thompson & Glanzman (1976)Two types of spinal neurons involved in reacting to repetitive eliciting stimuli
Type H Type S
Overall behavioral response depends on the balance between these two factorsSeveral variables involved but stimulus intensity appears to be the most influential
Davis (1974)ProcedureTwo groups of rats tested for startle response
Similar startle-eliciting tones (110 decibels)Background noise level
Different levels – either 60 or 80 decibelsResultsQuieter background showed habituation; louder background showed sensitization
See next slide
Davis (1974)
InterpretationLoud background noise level activated the Type S neurons to a degree that counteracted the habituation that was occurring in the Type H neurons
Results
A second physiological approach looks at underlying synaptic events related to learning
Aplysia, ocean-dwelling slug
Aplysia Simple snail with few neuronsHowever, nerve cells are relatively large; functions are knownUses a siphon to take in sea water from which food is filtered; can be withdrawn back into the body in times of dangerStimulation of siphon (touch or squirt from water jet) elicits this withdrawal
Kandel (2006)Both dishabituation and spontaneous recovery of siphon withdrawal to tactile stimulation was witnessedAfter six touches, responding nearly ceased (habituation)A light is then flashedResponding occurs to next touch (dishabituation)Later light is flashedNot much response60:00 rest interval – responding occurs to next touchShortly, later rehabituationLight stimulus again presented with same results as before
Sokolov (1963)We have a comparator mechanism in our brain which compares current sensory input to the model stored in memory to determine whether the stimulus is familiar
Theories of Wagner (1976; Whitlow & Wagner, 1976) and Olson (1976) elaborate on memory systemDual Memory TheoryPosit that a stimulus could be represented in short-term memory (STM), long-term memory (LTM), or bothDurable habituation seen across sessions or long interstimulus intervals reflects the formation of a long-term representation of the stimulusAlso, stimulus may be recognized if it has just occurred (STM)
Dual Memory Theory
Habituation: Massed presentations > Spaced presentations
Massed (STM & LTM) Spaced (LTM)
Because habituation is a relatively enduring change in central nervous system that occurs in many species and response systems, it demands much greater attention by experimental psychologists than it has received so farThe ability to disregard often-repeated, largely unimportant stimuli is likely linked to survival Habituation may pave the way for animals to attend to more important events: novel stimuli or those heralding significant events like food, mates, and predators
Exposure to a stimulus can affect later learning of that stimulusEasier to use a familiar stimulus for new learning than attempting new learning with an unfamiliar stimulusOnce we have learned to perceive a particular stimulus, we are better able to learn other things about that stimulusBut sometimes its not so easy to recognize and identify a stimulus See next slide
Nickerson & Adams (1979)
Presenting contrasting stimuli Different presentations help with
distinctionTransfer from easy to difficult
stimuli Easy trials seem to help with the more
difficult onesAttention and feedback
Intention to focus on differences and feedback concerning correctness helps
Preference for familiar stimuliPriming facilitationPotentiated startle
Mere exposure effect Increased liking of familiar stimulus
Herman Miller Aeron Chair
Wiggs (1993)ProcedureTested the “liking” of Japanese ideogram stimuliParticipants: College-aged and elderly from USComplex symbols originally presented for two seconds Later these and new symbols were presentedResults Stimuli seen three times previously were more liked than stimuli seen once or never before
Examples of ideogram stimuli used in this experiment
Wiggs (1993)
InterpretationWe seem to be attracted to things we are familiar with
Results
Kunst-Wilson & Zajonc (1980)ProcedureFlashed pictures at subliminal speedsLater shown some pictures that were previously presented and some that were notResultsIdentification was at chanceLiking was consistent for previously shown picturesInterpretationConscious recall not necessary for perceptual learning to occur
Priming occurs when one when presentation of a stimulus facilitates the processing of a closely following repetition of the same or a related stimulus
Startle can be magnified when the startle stimulus occurs in the presence of other, background sources of arousalFor example, neural arousal elicited by the startle noise can combine with arousal due to nervousnessIn lab, high anxiety people produce larger startle responses to loud noises
Exposure used to help with phobiasSystematic desensitizationEmotional flooding (implosion)Virtual reality exposure therapies
Some slides of this presentation prepared with the help of the following websites:www.psychology.iastate.edu/~./.../aobrien/.../8-30-05.pptdogsbody.psych.mun.ca/2250/lecture%201.pptdogsbody.psych.mun.ca/2250/lecture%202.pptwww.psychology.nottingham.ac.uk/staff/cmb/.../mlp2.ppt
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