PSYC 2330 Chapter Notes - Chapter 2: Supernormal Stimulus, Reflex Arc, Posttraumatic Stress Disorder

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Chapter 2
Afferent Neuron a neuron that transmits messages from sense organs to the central nervous system; also called a sensory neuron.
Efferent Neuron a neuron that transmits impulses to muscles; also called a motor neuron.
Interneuron a neuron in the spinal cord that transmits impulses from afferent (or sensory) to efferent (or motor) neurons.
Appetitive Behaviour behaviour that occurs early in a natural behaviour sequence and serves to bring the organism in contact with a
releasing stimulus
1. General Search Mode earliest component of feeding behaviour sequence, in which organism engages in non-directed
locomotor behaviour (form of appetitive behaviour)
2. Focal Search Mode second component of feeding behaviour sequence, in which organism engages in behaviour focused on
particular location/stimulus that is indicative of the presence of food (form of appetitive behaviour)
Consummatory behaviour behaviour that serves to bring a natural sequence of behaviour to consummation or completion.
Consummatory responses usually species-typical model action patterns
3. Food Handling Mode last component of feeding behaviour sequence, in which organism handles and consumes food.
Fatigue temporary decrease in behaviour caused by repeated/excessive use of muscles involved. (see figure below)
Habituation Effect progressive decrease in vigor of elicited behaviour that may occur with repeated presentations of eliciting stimulus.
Habituation process neural mechanism activated by repetitions of stimulus that reduces magnitude of responses elicited by that
stimulus.
Modal Action Pattern (MAP) a response pattern exhibited by most, if not all, members of a species in much the same way. Modal
actions patterns are used as basic units of behaviour in ethological investigations of behaviour.
Opponent Process a compensatory mechanism that occurs in response to the primary process elicited by biologically significant events.
The opponent process causes physiological behavioural changes that are the opposite of those caused by the primary process. (also called
b process) (see figure below)
Primary Process the first process that is elicited by a biologically significant stimulus. (also called a process)
Reflex Arc neural structures consisting of sensory neuron, interneuron, and motor neuron that enables stimulus to elicit reflex response.
(see figure below)
Sensitization Effect increase in vigor of elicited behaviour that may result from repeated presentations of eliciting stimulus/exposure to
strong extraneous stimulus.
Sensitization Process a neural mechanism that increases the magnitude of responses elicited by a stimulus.
Sensory Adaptation temporary reduction in sensitivity of sense organs caused by repeated/excessive stimulation. (see figure below)
Sign Stimulus specific feature of object/animal that elicits modal action pattern in another organism. (also called releasing stimulus)
Spontaneous Recovery recovery of a response produced by a period of rest after habituation or extinction.
S-R System shortest neural pathway, connects sense organs stimulated by eliciting
stimulus and muscles involved in making elicited response.
State System neural structures that determine general level of
responsiveness/readiness to respond of organism.
Supernormal Stimulus artificially enlarged/exaggerated sign stimulus that elicits
unusually vigorous response.
The concept of reflex
A reflex involves 2 closely related, linked events: an eliciting stimulus and a
corresponding response. Presentation of the stimulus is followed by the response and
the response rarely occurs without the stimulus. (ex. Puff of air causes eye to blink, tap
on knee causes leg to kick, etc.)
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The environmental stimulus for a reflex activates a sensory neuron (afferent neuron), which transmits the sensory message to the spinal
cord. The neural impulses are then relayed via the interneuron to the motor neuron (efferent neuron) which activates the muscles
involved in the response. These make up the reflex arc which represents the fewest neural connections necessary for reflex action.
Reflexes constitute much of the behavioural repertoire of a newborn. Head-turning reflex; if you touch your finger to a newborns face
they will reflexively turn towards it, probably evolved to facilitate finding the nipple. Respiratory occlusion reflex; which is stimulated by
a reduction of airflow (by something covering their face, mucous buildup, etc.). In response the baby first pulls head back, then wipes face
and then cries (vigorous expulsion of air) all to remove whatever was obstructing the airway. Milk-letdown; triggered initially by suckling
but eventually can also be stimulated by cues that reliably predict the infants suckling (ex. Time of day, crying).
Modal Action Patterns (MAPs)
These are species-typical response sequences that include sexual and nursing behaviours, territorial defense, aggression and prey capture.
The threshold for eliciting such behaviours varies and is dependent on the physiological state of the animal and its recent actions. Initially
identified as fixed action patterns to emphasize that the activities occurred pretty much the same way in all members of a species (Lorenz
and Tinbergen), but have since be seen that they are not performed in exactly the same fashion each time.
The stimulus responsible for a MAP can be difficult to isolate than that of simple reflexes if the response occurs in the course of complex
social interactions. For example, herring-gull chicks pecking the parent’s beak to stimulate food regurgitation what stimulates the
pecking behaviour? Is it the colour, shape or length of the bill, noises made, head movements, etc. or maybe none of them. The specific
features that were found to be required to elicit the pecking behaviour are called the sign stimulus (releasing stimulus) for this behaviour.
Once a sign stimulus had been identified, it can be exaggerated to elicit an especially vigorous response called a supernormal stimulus.
An example in humans is post-traumatic stress disorder (PTSD) or any other traumatic event. Cosmetic and perfume industries take
advantage of sign stimuli that elicit human attraction and affiliation (olfactory stimuli, red lipstick, breast enhancement, etc.).
Sequential Organization of Behaviour
Individual actions are organized into functionally effective behaviour sequences (ex. squirrels steps to obtain food). Motivated behaviours
foraging for food, finding a potential mate, defending a territory, feeding young, etc. Ethologists called early components of a
behaviour sequence appetitive behaviour and then end components consummatory behaviour (completion). Examples: chewing and
swallowing = foraging for food, hitting and biting =defensive. Consummatory behaviours are highly stereotyped, tending to be species-
typical MAPs while appetitive behaviours are less stereotyped, more variable and apt to be shaped by learning. As is evident of ethnic
cuisine, people of different cultures have many different ways of preparing food (appetitive), but all pretty much chew and swallow the
same way (consummatory). Important to understanding how behaviour is altered by learning.
In considering how animals obtain food, ex., now common to subdivide appetitive behaviours into a general search mode (doesn’t know
where to look for food) followed by a focal search mode (found a pecan tree) and then ending with consummatory behaviours or food
handling and ingestion mode.
Effects of Repeated Stimulation
Descartes thought, reflexive behaviour was unintelligent in the sense that it was automatic and invariant. According to his reflex
mechanism, each occurrence of the eliciting stimulus would produce the same reflex reaction because the energy of the eliciting stimulus
was transferred to the motor response through a direct physical connection. Elicited behaviour is not invariant!
Salivation and Hedonic (like/dislike food) Ratings of Taste in People
Study: A small amount of one flavor (lemon or lime) was placed on the tongues of 8 women for 10 trials. They were asked to rate how
much they liked/disliked sample and salivation was measured. Salivation in response to taste increased slightly from trial 1 to 2 but then
systematically decreased from trail 2 to 10. A similar decrease was seen in hedonic ratings. Trial 11 the flavor was changed (switched
lemon/lime) and a dramatic recovery in salivation and hedonic ratings was seen.
The decline in responding that occurs with repeated presentation of a stimulus is called habituation effect. The study showed us a
number of important things: 1) elicited behaviour is not invariant across repetitions of the eliciting stimulus. 2)habituation was stimulus
specific.
Helps chefs in preparing foods avoiding habituation effects providing each bite with a different flavor.
Weight loss - to reduce eating then promote habituation effects avoid variation in flavours.
Another study was completed which showed that if a child’s attention was diverted from the taste presentations, they showed much less
habituation to the flavor, helps us understand why people eat more infront of the TV.
Visual Attention in Human Infants
Visual cues elicit a looking response, which can be measured by how long the infant keeps his/her eyes on one object before shifting gaze
elsewhere.
Study: 4-month old infants were situated in front of two panels one 4x4 checkerboard, one 12x12 checkerboard for 10 seconds. 4x4
elicited a response that gradually decreased after each exposure (habituation). 12x12 checkerboard initially elicited an increase in
attention (sensitization) and then habituated. Showed us that visual attention elicited by a novel stimulus changes as babies gain
familiarity with the stimulus.
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