Chapter 2 - Elicited Behavior, Habituation,
Elicited behavior is behavior
which happens in response to some environmental event. This chapter
looks at changes in innate behaviors. Throughout the rest of the course,
we will talk about changes in learned behavior.
The Nature of Elicited Behavior
You will see that the the term "reflex"
typically refers to innate behaviors that are elicited by stimuli. This
first section discusses the simple reflex arc,
which consists of a sensory, or afferent,
neuron, at least one interneuron, and a motor,
or efferent, neuron.
Some types of reflexes can be quite complex and specific
to individual species. These are then called modal
action patterns (MAPs) or fixed action patterns
(the more common, but less preferred name). These reflexes are elicited
by sign stimuli, or releasing
stimuli, in the environment, and many very cleverly designed
experiments have been conducted to determine exactly what the sign stimulus
is in any given situation. You would learn more about this in a course
on comparative psychology, or ethology.
Effects of Repeated Stimulation
This section introduces the notion that even innate reflexes
can be modified by experience. Repeated exposure to the eliciting stimulus
can either decrease or increase the size of the response. The section
is basically setting the stage for the next section.
The Concepts of Habituation and Sensitization
In general, habituation is a
decrease in the size of an innate response to a stimulus resulting from
exposure to the stimulus. Sensitization is
an increase in the size of the response. We will talk about these processes
in detail in class. Be sure to understand the distinction between habituation
and sensory adaptation and response
Habituation and sensitization are controlled by different
mechanisms, as described in the dual-process theory.
Habituation is a function of the S-R system,
or changes in the neurons controlling the response, whereas sensitization
is a function of the state system, or changes
in the state of arousal of the organism. Most changes in behavior as
a result of repeated exposure to the stimuli are a combination of the
Characteristics of Habituation and Sensitization
Understand the distinctions between short-term
habituation and long-term habituation.
The obvious difference is the durability of the habituation; habituation
lasts either for a short time or a long time. Long-term habituation
is what we typically think of as learning, because it represents a relatively
stable and enduring change in behavior. These two types of habituation
may be products of different neural mechanisms.
The descriptions of stimulus generalization
and stimulus specificity of habituation are
important and straightforward.
Dishabituation can occur when
the animal's state of arousal is enhanced. If so, we see an increase
in the response that had become habituated.
Changes in Complex Emotional Responses
This final section introduces an interesting theory about
how emotional states that are elicited by stimuli can change as a result
of repeated exposure to the stimuli. We will talk about this theory
in class, discussing in detail the interactions of the a
and b processes.