Chapter 2: Elicited behavior, Habituation, and sensitization

• Elicited Behavior– behavior is a reaction to a stimulus in the

environment. • Food salivation• Bright light pupil dilation.

• The simplest form of elicited behavior is the reflex.• Components of a Reflex Arc• All reflex arcs have five essential components

– 1. receptor • reacts to a stimulus.

– 2. The sensory (afferent) neuron • conducts message to CNS

– 3. The integration center • consists of one or more synapses in the CNS.

– 4. The motor (efferent) neuron • conducts from CNS to an effector.

– 5. The effector, • muscle fibers or glands,

– contracts or secretes.

• The reflex arc just described = simplest situation. – Often other neural connections are involved.

• Notice that the Reflex arc does not require any willful conscious act – Thus - elicited

• Reflexes appear to have evolved to protect the well being of the organism.– withdrawal from pain– eyeblink– pupillary reflex– Sneeze, cough, vomit– patellar reflex– rooting reflex.– salivation– release of digestive fluids.

• Animals with reflexive tendencies had an advantage

• Ethology and Modal Action Patterns– Ethologists study the role of behavior within

the context of species-specific behaviors.• This is in contrast to the general processes

approach used by most psychologists• Ethologists

– behavior is generally instinctive.– often study animals in the wild rather than the

laboratory

• Consummatory behaviors– behaviors that are crucial for survival.

• feeding, courting, reproducing, and care for offspring.– innate, genetically determined survival behaviors.

• For Example– Imprinting.

• Konrad Lorenz•  Why do geese imprint, but other birds/animals

(robins) do not?– Precocial vs Altricial?

• Ethologists try to find the variables that are responsible for eliciting the behavior.– imprinting = two important factors.

• 1. The object must be moving• doesn’t matter if it is living or not

– ultra lights

• 2. The imprinting must occur within a critical period• (13-16 hours after hatching).

• Critical Period for learning some things for humans?– language

• Modal Action Patterns. (MAP’s)– modern Ethology abandoned the term instinct

• MAPs vs Reflexes– MAPs are

• more complex• consist of a long series of reflex-like acts• more variable, though still stereotypic• less likely to be evident at or soon after birth.

• In addition, to qualify as a MAP, a behavioral sequence must meet four specific criteria according to Moltz (1963)– 1. Stereotyped

• occurs the same way each time– 2. continue to completion once begun

• difficult to disrupt– 3. latent period

• once completed, some time must pass before behavior appears again

– 4. innate• the animal must perform the full integrated behavioral sequence the

first time its elicited

• Like Reflexes MAPs are highly adaptive• Protection from predators

– Cat – arch back, fluff hair, hiss• Protection against the elements

– Migration– hibernation

• getting food– Pigs rooting– spider webs

• courtship and mating– Big Horn Sheep– Ducks

• care for young– Birds

• Nests• Gathering food

– Wasps that capture spiders

• Modal Action Patterns are released by a sign stimulus – Sign stimulus

• a specific environmental event that triggers an MAP– Female pheromones often trigger mating behavior in males

• The sign stimulus works like a key to unlock an innate releasing mechanism– innate releasing mechanism

• a neural mechanism that is stimulated by a sign stimulus.• controls the modal action pattern

• Examples– Geese with Eggs

• Rolling away?• What if it slips on way back?

– stereotyped• Larger eggs?

– Supernormal stimuli

– Birds feeding young• Cowbirds

– Herring gull studies• Which beak works best?

• Do humans exhibit Modal Action Patterns?– sleep?

• Stereotyped?• continue to completion once begun?• latent period?• Innate?

– emotions?– sex?

• Effects of Repeated Stimulation– Descartes thought that a reflexive response

would occur the same way each time it was elicited

– However – elicited behavior are not invariant• Habituation.

– repeated exposure to a stimulus reduces responding to that stimulus.

• Habituation is a very simple form of learning

• Very useful tool for understanding animal and infant behavior.

• Can you distinguish between “ba” and “pa”– Infants?– Used suck rate as response

• Pacifier with an embedded switch

• As simple as habituation is, it can be used to tell us a lot about a nonverbal organism

• Other race effect– Caucasian infants (3.5 months old)– Group 1 (Caucasian faces)

• shown a Caucasian face until habituated– Group2 (Asian faces)

• Shown an Asian face until habituated– Test

• Both groups shown novel faces– New Caucasian face for group 1– New Asian face for group 2

Other-race effect in Caucasian infants

• HOWEVER,• Repetitive stimulation does not always cause habituation.

– sometimes you get sensitization. • My father and motorcycle

– emotional response• flee

– do not habituate– likely to be more responsive to other stimuli.

• tap on the shoulder• drop a wrench. 

• My dog and car AC

• Davis (1974)– sensitization and habituation to the same stimulus.– 110 db noise = loud.

• Gp1 = rats housed in a quiet chamber = 60 db• Gp 2 = rats housed in a loud chamber = 80 db

• One of the groups decreased their startle response to the 110 db noise after repeated presentations.

• The other group increased their startle response to the 110 db noise after repeated presentations.

– Which group is which?– What phenomenon does each group demonstrate?

• What determines whether we get habituation or sensitization?– Dual process theory

• Two simultaneous processes– S-R system

• Reflex arc – State system

• Involves additional parts of the nervous system that regulate levels of arousal

• The S-R system and State system are additive – but in opposite directions– The more active system will determine whether

habituation or sensitization is displayed• Example

– Checkerboard study in book.– Infants shown checkerboards

• 4 x 4• 12 x 12

• Habituation versus Sensory Adaptation and Response Fatigue

• Sensory Adaptation– Bright light – blinded– Loud noise – can’t hear

• Response Fatigue– Too tired to move

• Stimulus specificity– Habituation is stimulus specific

• Stop responding to one thing, but if there is a change in the stimulus the habituation goes away.

– Dishabituation

– Sensitization is not stimulus specific• If working in a loud factory you may be more reactive to

other stimuli– Tap on the shoulder

– This is consistent with dual process theory• S-R system = specific to sensory input• State system = general arousal

• Time course for habituation – Short-term = seconds to minutes– Long-term = may persist for many days– Leaton (1976)

• Startle response in rats to loud high pitched tone