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 intensity  Expectancy  Relevance  Potential 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 stimulation  Organisms decrease responding to a stimulus after repeated exposures  A simple form of learning in which the organism learns something about a single stimulus  Common examples:  Noises in your house  Traffic  Air conditioning/furnace

Most pervasive form of learning  Has received little attention compared to more complex forms of learning  Oversight may have resulted from belief that habituation is not “real” learning  Many 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 stimulation  However, there are some alternative explanations  We will discuss these later

Whole-Body Startle Reaction  Reaction to loud sounds is studied using laboratory animals  In rats, we can measure startle in a stabilimeter chamber  Rat jumps, chamber bounces and sensors detect the amount of movement

Skin Conductance Response  Electrodes placed on bodies of humans Siddle, Kuiack, & Kroese (1983) 

Eye Fixations to Novel Stimuli  Measurement of change in duration or number of eye fixations Novelty Recognition Task  New 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 occur  These researchers derived several parametric features of habituation See next few slides 

Number of repetitions of a stimulus  Exact number required for OR decrement varies considerably  Anywhere from one, to hundreds of presentations

If stimulus is not presented for a period of time, the OR tends to spontaneously recover  If the delay interval is sufficiently long, the OR may recover completely

Habituation occurs more quickly on each successive occasion Savings Effect  Amount 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 seconds  By 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 stimulus  The 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 (16 th time overall)  OR increases as compared to 15 th presentation; dishabituation has taken place  Presenting the tone again will lead to the reappearance of habituation; OR returns to previous low level

Habituation may spread to similar stimuli  The 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 presentation  Not 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 explanations  Seems 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

Sensitization  An increase in the magnitude of the OR as a result of repeated stimulation  Typically occurs only with very intense stimuli accompanied by physiological arousal  Multiple 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 factors  Several variables involved but stimulus intensity appears to be the most influential

Davis (1974) Procedure  Two groups of rats tested for startle response  Similar startle-eliciting tones (110 decibels)  Background noise level  Different levels – either 60 or 80 decibels Results  Quieter background showed habituation; louder background showed sensitization See next slide 

Davis (1974) Interpretation  Loud 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 neurons  However, nerve cells are relatively large; functions are known  Uses a siphon to take in sea water from which food is filtered; can be withdrawn back into the body in times of danger  Stimulation 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 witnessed  After six touches, responding nearly ceased (habituation)  A light is then flashed  Responding occurs to next touch (dishabituation)  Later light is flashed  Not much response  60:00 rest interval – responding occurs to next touch  Shortly, later rehabituation  Light 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 system Dual Memory Theory  Posit that a stimulus could be represented in short- term memory (STM), long-term memory (LTM), or both  Durable habituation seen across sessions or long interstimulus intervals reflects the formation of a long- term representation of the stimulus  Also, 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 far  The 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 stimulus  Easier to use a familiar stimulus for new learning than attempting new learning with an unfamiliar stimulus  Once we have learned to perceive a particular stimulus, we are better able to learn other things about that stimulus  But sometimes its not so easy to recognize and identify a stimulus See next slide 

Nickerson & Adams (1979)

 Presenting contrasting stimuli  Different presentations help with distinction  Transfer from easy to difficult stimuli  Easy trials seem to help with the more difficult ones  Attention and feedback  Intention to focus on differences and feedback concerning correctness helps

 Preference for familiar stimuli  Priming facilitation  Potentiated startle

 Mere exposure effect  Increased liking of familiar stimulus Herman Miller Aeron Chair 

Wiggs (1993) Procedure  Tested the “liking” of Japanese ideogram stimuli  Participants: College-aged and elderly from US  Complex symbols originally presented for two seconds  Later these and new symbols were presented Results  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) Interpretation  We seem to be attracted to things we are familiar with Results 

Kunst-Wilson & Zajonc (1980) Procedure  Flashed pictures at subliminal speeds  Later shown some pictures that were previously presented and some that were not Results  Identification was at chance  Liking was consistent for previously shown pictures Interpretation  Conscious 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 arousal  For example, neural arousal elicited by the startle noise can combine with arousal due to nervousness  In lab, high anxiety people produce larger startle responses to loud noises

Exposure used to help with phobias  Systematic desensitization  Emotional flooding (implosion)  Virtual reality exposure therapies

Some slides of this presentation prepared with the help of the following websites:   dogsbody.psych.mun.ca/2250/lecture%201.ppt  dogsbody.psych.mun.ca/2250/lecture%202.ppt 