PSYC 2330 Chapter Notes - Chapter 2: Startle Response, Supernormal Stimulus, Reflex Arc

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January 24th, 16
Principles of Learning
Chapter 2: Elicited Behaviour, Habituation, and Sensitization
Habituation and sensitization are important because they are potentially
involved in all learning procedures
The Nature of Elicited Behaviour
Most behaviour occurs in response to stimuli
Much of behaviour is elicited
Simplest form of elicited behaviour reflexive behaviour
The Concept of the Reflex
Reflex:
o Involves two closely related events: an eliciting stimulus and a
corresponding response
o Stimulus and response are linked
o Presentation of the stimulus is followed by the response and the
response rarely occurs without the stimulus
Specificity of the relation between a stimulus and its reflex response is a
consequence of the organization of the nervous system
In vertebrates (including humans) simple reflexes are normally mediated by
three neurons:
o Environmental stimulus for a reflex activates a sensory neuron
(also called afferent neuron) transmits sensory message to the
spinal cord neural impulses relayed to an interneuron relays
the impulses to the motor neuron (also called the efferent neuron)
activates the muscles involved in the reflex response
Sensory and motor neurons rarely communicate directly
o Impulses from one to the other are relayed through at least one
interneuron
o Neural circuitry ensures that particular sensory neurons are
connected to a corresponding set of motor neurons
o Because of this restricted wiring a particular reflex response is
elicited only by a restricted set of stimuli
Afferent neuron + interneuron + efferent neuron = reflex arc
o Reflex arc in vertebrates represents the fewest neural connections
necessary for reflex action
o BUT sometimes additional neural structures may be involved
o Sometimes the occurrence of even simple reflexes can be influenced
by higher nervous system activity
Reflexes keep us alive
o Ex. Suckling in infants one of the most prominent reflexes in infants
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Modal Action Patterns
Simple reflex responses (ex. Startle reactions to loud noises) are evident in
many species
BUT other forms of elicited behaviour occur in just one species or in a small
group of related species
Modal action patterns (MAPs): Response sequences that are typical of a
particular species
Species-typical MAPs have been identified in many aspects of animal
behaviour including sexual behaviour, territorial defence, aggression, and
prey capture
Important feature of MAPs: threshold for eliciting such activities varies
o The same stimulus can have different effects depending on the
physiological state of the animal and its recent actions
Eliciting Stimuli for Modal Action Patterns
Stimulus responsible for an MAP can be difficult to isolate if the response
occurs in the course of complex social interactions
Essential features called sign stimulus or releasing stimulus
o Once a sign stimulus is identified it can be exaggerated to elicit an
especially vigorous response
o An exaggerated sign stimulus is called a supernormal stimulus
Sign stimuli originally identified in studies with non-human subjects but
they also play a major role in the control of human behaviour
Responding effectively to danger has been critical in the evolutionary history
of all animals (including humans)
o Traumatic events have come to elicit strong defensive MAPs
o Early components of the defensive action pattern include eyeblink
reflex and the startle response
Sign stimuli and supernormal stimuli also have a major role in scoail and
sexual behaviour
o MAPs involved in sexual arousal and copulation are elicited by visual,
tactile, olfactory, and other types of sign stimuli that are specific to
each species
The Sequential Organization of Behaviour
Individual actions are organized into functionally effective behaviour
sequences
All motivated behaviour involves systematically organized sequences of
actions
According to ethologists:
o Appetitive behaviour: early components of a behaviour sequence
o Consummatory behaviour: end components of a behaviour
sequence
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Consummatory meant to convey the idea of
consummation or completion of a species’ typical response
sequence
Appetitive responses occur early in behaviour sequence
serve to bring the organism into contact with the stimuli that
will release the consummatory behaviour
Consummatory responses highly stereotyped species typical
behaviours that have specific eliciting or releasing stimuli
Appetitive behaviour more variable and can take a variety of
different forms depending on the situation
Ex. A squirrel can run up one side or the other or jump
from a nearby tree (appetitive behaviour) BUT the
chewing and swallowing responses that it makes are
fairly stereotyped (consummatory responses)
Ex 2. People of different cultures have many different
ways of preparing food (appetitive behaviour) but they
all pretty much chew and swallow in the same way
(consummatory behaviour)
Ex 3. Actions that are considered to be rude and
threatening (appetitive defensive responses) differ
from one culture to another BUT people hit and hurt
one another (consummatory defensive behaviour) in
pretty much the same way regardless of culture
Consummatory responses tend to be species-typical MAPs
Appetitive behaviours are more variable and more apt to be
shaped by learning
Ex. Animals obtaining food:
o Common to characterize the foraging response sequence as:
1. General search mode
Animal does not yet know where to look for food
Not spatially localized
Once the animal has found a food source it will switch to
the next mode
2. Focal search mode
Begin to search for food only in that location (ex. Only in
that pecan tree)
Characterized by greater spatial specificity than general
search
3. Food handling and ingestion mode
Once focal search behaviour has led to food behaviour
changes to food handling and ingestion mode
(consummatory behaviour)
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