PS261 Chapter Notes - Chapter 2: Habituation, Efferent Nerve Fiber, The Reflex
Chapter Two – Elicited Behaviour, Habituation, and Sensitization
Chapter 2.2 − The Nature of Elicited Behaviour
- Elicited Behaviour:
o Occurs in response to stimuli
▪ Reflexive
o Ex. irritation of respiratory passages causes sneezing and coughing
2.2.a: Reflexes
- Concept of the Reflex
o Involves two closely-related events
▪ Eliciting Stimulus
▪ Corresponding Response
• Stimulus and response are linked
o The specificity of the relation between the stimulus and accompanying reflex
response is a consequence of nervous system organization
o Environmental stimulus for the reflex activates sensory organ – afferent neuron
▪ Transmits sensory message to spinal cord
• Neural impulses related to motor neuron – efferent neuron
o Activates muscles involved in reflex response
o Sensory and motor neurons rarely communicate directly
▪ Impulses from one to the other are relayed through at least one interneuron
o Neural circuitry ensures that particular sensory neurons are connected to the
corresponding set of motor neurons
▪ Restricted Wiring: restricted set of stimuli elicits particular reflex response
..b: The Reflex Arc
o Reflex Arc: represents the fewest neural connections necessary for reflex action
▪ Afferent neuron, interneuron, and efferent neuron
o Respiratory Occlusion Reflex: stimulated by reduction of air flow to baby
▪ When cloth covers babys face or accumulation of mucus in nasal passages
▪ Reactions:
• Pull head back
• Face-wiping motion
• Crying involves vigorous expulsion of air
▪ Essential for survival
..c: Modal Action Patterns
- Modal Action Patterns
o Simple reflex responses are evident in many species
▪ Papillary constriction to bright light
▪ Mammalian infants suck in response to object being placed near mouth
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▪ Herring-gull chicks are just as dependent on parental feeding
• Chicks peck at tip of parents bill
o Parents regurgitate
▪ Chicks peck regurgitated food
o Modal Action Patterns (MAP): response sequences that are typical for a particular species
▪ Identified in many aspects of animal behaviour
• Sexual Behaviour
• Territorial Defense
• Aggression
• Prey Capture
o The threshold for eliciting these activities varies
▪ Same stimuli have different effects depending on the physiological state of
the animal and its recent actions
o Lorenz and Tinbergen:
▪ Species-specific action patterns as fixed action patterns to emphasize the
activities that occurred pretty much the same way in all members of a species
- Eliciting Stimuli for Modal Action Patterns
o Fairly easy to identify in case of simple reflexes
▪ The stimulus responsible for modal action pattern can be more difficult to
isolate if the response occurs in the course of complex social interactions
o Pecking by chicks may be elicited by:
▪ Colour and shape/length of parents bill, noises parent makes, head
movements of the parent or other stimuli
▪ Tinberg and Perdeck:
• Beak had to be a long, thin, moving, downward-facing object with a
contrasting red patch near tip
o Sign Stimulus or Releasing Stimulus
▪ Specific features are found to be required to elicit pecking behaviour
▪ Once identified, they can be exaggerated to elicit especially vigorous response
• Supernormal Stimulus: exaggerated sign stimulus
▪ Sign stimuli play a major role in the control of human behaviour
• Also play a major role in social and sexual behaviour
..d: Behaviour Sequences
- Sequential Organization of Behaviour
o Responses do not occur in isolation of one another
o All motivated behaviour involves systematically organized sequences of actions
o Appetitive Behaviour: early components of behaviour sequence
▪ Occur early in behaviour sequence and serve to bring organism into contact
with stimuli that will release consummatory behaviour
▪ Less stereotyped and can take variety of different forms, depending on situation
▪ More variable and can be shaped by learning
o Consummatory Responses: end components of behaviour sequence
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▪ Completion of a species typical response sequence
▪ Highly stereotyped, specific behaviours of a species
• Have specific eliciting or releasing stimuli
▪ Species-typical modal action patterns
o Ex. Foraging for Food
▪ Appetitive Response
• General Search Mode: occurs when the subject does not know
where to look for food
• Focal Search Mode: once it finds a source, it begins to search for the
food in/on the source only
▪ Consummatory Response
• Food Handling and Ingestion Mode: once the food has been found,
then this mode activates
Chapter 2.3 − Effects of Repeated Stimulation
- Reflex Mechanism – according to Descartes
o Each occurrence of eliciting stimulus would produce the same reflex reaction,
because the energy of the eliciting stimulus was transferred to motor response
through direct physical connection
▪ If this was true, it would be of limited interest to researchers
..a: Four Examples of Variation in Elicited Response Over Time
1. Salivation & Hedonic Ratings of Taste in People
- Epstein et al., 1992
o The taste of food elicits salivation as a reflex response
o Salivation and hedonic ratings are decreased with repeated trials
▪ Habituation Effect: decline in response with repeated stimulus presentation
• Prominent feature of elicited behaviour is evident in virtually all
species and situations
• Decrease in response specific to habituated stimulus only
o Stimulus-specific
▪ The taste of stimulus influences the rate of taste habituations
o Having attention directed to non-food cues keeps food from losing flavour through
habituation
2. Visual Attention in Infants (4-month old)
- Bashinski et al., 1985
o Visual cues elicit a looking response and can be measured by how long they keep
their eyes on one object before shifting their gaze
o The nature of the change is determined by the nature of the stimulus
▪ Sensitization is observed depending on the complexity of the stimulus
o People are experts at recognizing and remembering faces
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