Mazur Chapter 2: Innate Behavior Patterns and Habituation Flashcards
Overview
Many learned behaviors are derivatives, extensions, or variations of innate behaviors
Many of the features of learned behaviors (e.g. their control by environmental stimuli, their mechanisms of temporal sequencing) have parallels an inborn behavior patterns
Most of the examples of innate behavior patterns are based on the work of ethologists – scientists who study how animals behave in their natural environments
Ethologists are interested in both learned and innate behaviors
Many of the behavior patterns they’ve studied in detail are species specific
Control Systems Theory
Branch of science that deals with goal-directed behaviors in both living creatures and inanimate objects
A common example of an inanimate goal-directed system is a house’s heating system, often called a feedback system or a closed-loop system
Components of of feedback system:
Comparator Reference Input Actual Input Action System Output Disturbance
Comparator
Thermostat, receives two types of information:
Reference input
Actual input
Reference Input
Conceptual entity
The temperature that, when reached, will be just enough to open a switch and stop the furnace
Actual Input
Measures some actual physical characteristic of the present environment
Action System
The comparator’s response to input
e.g. the thermostat’s command to activate the furnace
Output
The product of the action system
e.g. warm air entering the room from the activated furnace
Disturbance
An extraneous variable that affects the actual input
e.g. cold air coming in from an open window
Reflex
Stereotyped pattern of movement of a part of the body that can be reliably elicited by presenting the appropriate stimulus
Flexion Reflex
Very rapid withdrawal of the hand (e.g. from a hot stove) by bending of the arm at the elbow
Response is very rapid because the association between sensory and motor neurons occur directly in the spinal cord
In the flexion reflex, one or more small neurons, called interneurons, separate sensory neurons from motor neurons
The motor neurons have cell bodies within the spinal cord and their axons exit the front of the spinal cord and travel back down the arm, and synapse with individual muscle fibers in the arm
The physiology of the flexion reflex is referred to as the spinal reflex arc
Flexion Reflex & Control Systems Theory
Within the muscles of the arm are structures called stretch receptors, which serve as the comparators of the feedback system
The stretch receptors compare the reference input (command sent from the motor neurons to the muscle fibers telling them to contract) and the actual amount that the muscles have contracted
If the muscles have not contracted sufficiently for any reason, stretch receptors begin to stimulate the motor neurons until the contraction is completed
The comparators (the stretch receptors) continue to stimulate the action system (motor neurons and muscle fibers), until the goal is achieved (a successful muscle contraction)
Tropisms and Orientation
Whereas a reflex is the stereotyped movement of a part of the body, a tropism is a movement or changing orientation of the entire animal
Jacques Loeb (1900) called tropisms “forced movements” to suggest that no intelligence, will, or choice was involved
Tropisms were later separated into two major categories: Kineses and Taxes
Kinesis
The direction of the movement is random in relation to a stimulus
e.g. wood louse does not head directly toward a moist area or away from a dry one, because it has no means of sensing humidity of a distant location – it can only sense the humidity of its present location
This is an example of a feedback system: it must have a comparator that can detect the actual input (current humidity) and compare it to the reference input (the goal of high humidity)
The action system is the creature’s locomotion system – motor neurons, muscles and legs that allow it to move about
Locomotion is the output of this action system, but there is no guarantee that locomotion will lead to the goal of high humidity
Kinesis also help to keep creatures away from predators
• E.g. slugs moving when sensing chemical produced by predatory beetle
Taxis
Unlike kinesis, in taxis, the direction of movement bears some relationship to the location of the stimulus
e.g. maggot’s taxis points the organism in a single direction away from light
e.g. ants use the sun as a navigational aid when traveling to or from home
• on a journey away from home, the ant travels in a straight path by keeping the sun at a constant angle to its direction of motion
• to return home, the ant later changes the angle by 180°
Fixed Action Patterns: 3 main characteristics
A fixed action pattern is a part of the repertoire of all members of the species, and it may be unique to that species
The animal’s ability to perform the behavior is not a result of prior learning experiences
In a sequence of behaviors, the behaviors occur in a rigid order regardless of whether they are appropriate in a particular context; that is, once a fixed action pattern is initiated will continue to completion without further support from environmental stimuli
Sign Stimulus
Specific stimulus which initiates a fixed action pattern
Research has revealed which features of the stimulus are important and which are irrelevant to the initiation of a fixed action pattern
e.g. contagious yawning – only works when we see the entire face of a yawning person (not just the eyes or mouth)
e.g. stickleback fish (Tinbergen, 1951) – defends territory against other male sticklebacks, which all have a red patch on their underside
• If the red patches are not observed (either female, or obscured by experimenter), the behavior is not initiated
Sometimes an unrealistic model can elicit strong response than the actual sign stimulus – e.g. larger models of male sticklebacks are found more attractive by females; much larger oyster catcher bird eggs initate f-a-p of rolling back to nest instead of smaller, natural egg: “supernormal sign stimulus”
Reaction Chains
Whereas fixed action patterns continue to completion once started, in a reaction chain, the progression from one behavior to the next depends on the presence of the appropriate external stimulus
If the stimulus is not present, the chain of behaviors will be interrupted
If the stimulus for behavior in the middle of the chain is presented at the outset, the earlier behaviors will be omitted
o e.g. hermit crab finding a new shell
The distinguishing characteristic of reaction chains is that the performance of one behavior usually produces the stimulus that elicits the next behavior in the chain
Unlike the behaviors of the fixed action pattern, those of a reaction chan do not always occur in a complete sequence
The sequence can stop at any point if the stimulus required for the next step is not forthcoming
Innate Human Abilities and Predispositions
Although human beings have a variety of reflexes, plus a few fixed action patterns and other important behaviors, these innate responses certainly constitute a very small portion of what we do—almost all of our daily behaviors are products of our learning experiences
Steven Pinker: all human beings have in common the large set of inborn abilities, tendencies, and predispositions, which collectively might be called “human nature”
o Children of all cultures babble before they learn to speak, and even deaf children babble at an early age
• These and other cross-cultural universals have been used as evidence for an innate human ability to acquire language
Another aspect of human behavior that may be innate is the range of emotions people experience, how emotions are reflected in the facial expressions, and how others interpret these facial expressions.
Darwin (1872) first proposed the different emotions may have evolved because they help creatures survive, and that gestures and facial expressions of emotion are important means of social communication among members of a species
see: “Human Universals”
Human Universals
Abilities or behaviors that are found in all known human cultures
Anthropologist Donald Brown (1991) compiled a list of 400 items which includes very specific behavior such as dance, music, death rituals, hygienic care, jokes, and folklore, as well as some major characteristics of human life, such as marriage, inheritance rules, toolmaking into use, government, sections are crimes, and division of labor
Since these characteristics of human systems are found in all cultures, even those that are completely isolated from the modern world, they most likely reflect innate human tendencies
Habituation, general
“A decrease in the strength of a response after repeated presentation of a stimulus that elicits the response”
In principle, any elicited response can exhibit habituation, but in practice, habituation is most evident in the body’s automatic responses to new and sudden stimuli
e.g. Startle reflex in response to gunshots
Orienting Response
If a new sight or sound is presented to a dog or other animal, the animal may stop its current activity, lift its ears and head, and turn in the direction of the stimulus.
If the stimulus is presented repeatedly but is of no consequence, the orienting response will disappear.
Similarly, if an infant is played a tape recording of an adult voice, the infant will turn its head and direction of the sound
However, if the same word is played over and over, the infant will soon stop turning toward the sound
Stimulus Specific Characteristic of Habituation
Distinguishes habituation from both sensory adaptation and muscular fatigue
A basic function of habituation is to allow the organism to be able to ignore the many insignificant stimuli that it repeatedly encounters
Being continually startled or distracted by such stimuli would be a waste of the organism’s time and energy
An organism that was unable to habituate to insignificant stimuli would probably have a difficult time attending to more important stimuli
There is evidence that the rate of habituation in human infants and children is correlated with mental abilities later in life
The usefulness of habituation is also witnessed by its universality throughout the animal kingdom – habituation can be seen in hydra, which contain some of the most primitive nervous system was found on our planet
General Principles of Habituation
Course of Habituation
Effects of Time
Relearning Effects
Effects of Stimulus Intensity
Effects of Overlearning
Stimulus Generalization
Course of Habituation
The decrements in responding from trial to trial our large at first but get progressively smaller as situation proceeds
Effects of Time
The response will recover if after habituation the stimulus is withheld for some period of time
The amount of recovery of the response depends on the amount of time that elapses
Relearning Effects
Habituation should proceed more rapidly in a second series of stimulus presentations
In further series of stimulus presentations, habituation should occur progressively more quickly
Effects of Stimulus Intensity
Habituation pursues more rapidly with weaker stimuli
If the stimulus is very intense, there may be no habituation at all
Effects of Overlearning
Further learning can occur at time when there’s no longer any change observable behavior
Thompson and Spencer called this “below-zero habituation” because it occurs at a time when there’s no observable response to the stimulus
Stimulus Generalization
The transfer of habituation from one stimulus to new but similar stimuli
The amount of generalization depends upon the degree of similarity between stimuli
It is always the subject, not the experimenter, who is the ultimate judge of similarity
For this reason, psychologists can use habituation as a tool to determine exactly which stimuli an individual find similar
e.g. Johnson and Aslin (1995), understood that infants treated the original stimulus as a solid rod moving behind the box even though the middle part of the rod could not be seen
Physiological Mechanisms of Habituation
Simple Systems Approach
Simple systems approach—strategy of studying fairly primitive creatures which have nervous systems that are smaller and less complex
e.g. Kandel and the aplysia
o Habituation of gill-withdrawal reflects
o Discovered that it was a decrease in excitatory conduction which occurred at the synapses involving the axons of the sensory neurons
o Researchers found that there was no change in the postsynaptic neurons sensitivity to the transmitter
• What changed was the amount of transmitter released by the presynaptic neurons
o It is theorized that the influx of calcium ions into the axon terminals becomes progressively weaker with repeated stimulation of the sensory neuron
Kandel and the Aplysia
Habituation of gill-withdrawal reflects
Discovered that it was a decrease in excitatory conduction which occurred at the synapses involving the axons of the sensory neurons
Researchers found that there was no change in the postsynaptic neurons sensitivity to the transmitter
What changed was the amount of transmitter released by the presynaptic neurons
It is theorized that the influx of calcium ions into the axon terminals becomes progressively weaker with repeated stimulation of the sensory neuron
Physiological Mechanisms of Habituation
Research with Mammals
Experiment with rats’ startle response (Davis 1982) to a sudden loud noise show that changes during habituation take place in the early portions of the circuit
These findings are similar to those from the Aplysia:
Neurons undergo change during habituation on the sensory side of the circuit
Changes take place within the reflex circuit itself rather than being a result of new inputs from neurons elsewhere in the nervous system
There is growing evidence that many different areas of the brain and nervous system display habituation when the same stimulus is repeatedly presented: plasticity
Plasticity
The nervous system’s ability to change as the result of experience or stimulation
Plasticity—the nervous system’s ability to change as the result of experience or stimulation
Physiological studies of habituation demonstrate that plasticity is possible in many different levels of the nervous system
This sometimes results from chemical changes in existing synapses rather than from the growth of new synapses
Opponent Process Theory, Overview
Richard Solomon and John Corbit (1974)
With stimulus repetition, some emotional reactions weekend while others are strengthened
Theory is meant to apply to a wide range of emotional reactions
Stimulus produces sudden appearance of an emotional reaction, which quickly reaches a peak of intensity
This response gradually declines to a somewhat lower level, or plateau
With the offset of the stimulus, there’s a sudden switch to an emotional after- reaction that is in some sense the opposite of the initial emotion
This after-reaction gradually declines, and the individual’s emotional state returns to a neutral state
a-process
Largely responsible for the initial emotional response
Fast-acting response to a stimulus that rises to a maximum and remains there as long as the stimulus is present
When the stimulus is no longer present, the a-process decays very quickly
b-process
Totally responsible for the after-reaction
Activated only in response to the activity of the a-process, and it is more sluggish to rise and to decay
When both the a- and b- processes are active to some degree, the resulting emotional response can be predicted by simple subtraction
According to this theory, it is the rise in the b-process that causes the drop in initial emotional reaction from the peak to the plateau
When the stimulus ends, the a-process quickly decays, all that remains to b-process, which produces the emotional after reaction
Predictions offered by the opponent-process theory
With repeated exposures to stimulus, the primary emotional response exhibits a sort of habituation – it become progressively smaller
At the same time, there is a marked increase in the size and duration of the after-reaction
This changes the result of an increase in the size of the b-process
Whereas the a-process does not change, the b-process is strengthened with use, and weakened with disuse
With repeated stimulations, the b-process rises more quickly, reaches a higher maximum, and is slower to decay after the stimulus is terminated
• e.g., experienced parachutists who do not experience much anxiety but report feelings of exhilaration and euphoria that last for hours
• e.g., tolerance to the effects of drugs
Opponent Process Theory & Tolerance
According to the opponent-process theory, tolerance is the product of a strengthened b-process
The stronger b-process also explains why, with repeated opiate use, withdrawal symptoms become more severe, and they may last for weeks or longer
At this stage, the individual does not take the opiate for pleasure but for temporary relief from the withdrawal symptoms
In terms of the opponent process theory, each injection reinstates the a-process, which counteracts the withdrawal symptoms produced by the b-process
Unfortunately, each injection also further strengthens the process, so the individual is caught in a vicious cycle
Solomon & Corbit suggests that the b-process is the body’s mechanism of avoiding prolonged, intense emotions
Extremes of emotions, whether positive or negative, tax the body’s resources, so when any a-process persist for some time, the corresponding b-process is evoked to counteract it, at least in part
If this is indeed the function of the b-process, then the examples of addictive behaviors clearly demonstrate that this mechanism is imperfect
Criticism of opponent-process theory
The different examples used by Solomon & Corbit exhibit vastly different time courses
In the heart rate studies with dogs, the b-process lasts only seconds or few minutes
In an addiction, the b-process may continue for months
It may be very unlikely that the same physiological mechanisms are involved in emotional events whose durations differ by such great degrees
Defense of Opponent-Process Theory
As long as the emotional responses conform to the predictions of the theory, it doesn’t matter whether these patterns are based on a single physiological mechanism or a dozen different ones
On a descriptive level, the major characteristics of emotional episodes emphasized by opponent-process theory (the peak, the plateau, the after-effect, the changes with repeated stimulation) appear to be fairly well documented by case histories, systematic observations, and experiments
Whether or not these patterns share a common physiological mechanism, the data suggest that the theory captures some characteristics of emotional responses that are quite general
