Interaction of Learning and Instinct

Studies of habituation and sensitization have been especially helpful in clarifying
the physiological and genetic mechanisms that control various forms
of learning. Such investigations have also shown that habituation and sensitization
are widespread phenomena with tremendous adaptive significance
throughout the animal kingdom.
Ethologists, in marked contrast with psychologists (especially behaviorist
psychologists), historically have emphasized the importance of underlying
physiological mechanisms in the regulation of various behavioral phenomena.
Traditionally, they argued that many forms of behavior are not only genetically
determined, or innate, but further constrained by the physiological
hardware of the organism. They held that psychologists completely
ignored these factors by focusing on only the input and output of experiments.
Psychologists, on the other hand, have maintained that nearly all
forms of behavior are influenced in some way by learning. These contrasting
views, which developed largely as a result of different experimental approaches,
eventually gave way to a more modern and unified picture of behavior.
One area of research that greatly facilitated this unification was the study
of habituation and sensitization. By discovering the chemical and neurological
changes that take place during these simple forms of learning, neurobiologists
succeeded in demonstrating how the physiological environment
is modified during the learning process and that such modifications are remarkably
similar throughout the animal kingdom. Thus, it became quite
clear that an understanding of proximate physiological mechanisms was
central to the study of behavior and learning.
In addition, other studies on sensitization and habituation helped establish
the generality of these processes among various groups of animals. They
showed that simple forms of learning can occur in nearly all major animal
phyla, and that these learning processes often result in modification of simple
innate behaviors as well as a variety of more complex responses. From these and other studies, it was soon evident that learning and instinct are
not mutually exclusive events but two processes that work together to provide
animals with maximum adaptability to their environment. The kind of
learning that occurs during habituation and sensitization allows animals to
modify simple, fixed behaviors in response to repeated exposure to environmental
stimuli. Habituation allows an organism to filter irrelevant background
stimuli and prevent sensory overload and interference of normal activities
critical to its survival. Sensitization helps increase an organism’s
awareness of stimuli in the face of potentially dangerous situations.
These two forms of learning represent important behavioral adaptations
with tremendous generality in the animal kingdom. Even in humans, a variety
of seemingly complex behaviors can be attributed to interactions between
sensitization and habituation and the simple neurological changes
that accompany them.
Sources for Further Study
Domjan, Michael. Principles of Learning and Behavior. 5th ed. Belmont, Calif.:
Thomson/Wadsworth, 2003. Provides a complete treatment of the psychological
basis and mechanisms of learning. Chapter 3 is devoted entirely
to habituation and sensitization, and it provides several specific examples
of these processes in both human and animal subjects. Includes
many original data tables and graphs and a thorough review of the literature.
Grier, James W. Biology of Animal Behavior. 2d ed. New York: McGraw-Hill,
1992. This college-level text provides comprehensive treatment of the
study of animal behavior. Clearly written and well illustrated; should provide
a good introduction for the layperson. Six chapters are devoted to
the physiological control of behavior, and one chapter deals entirely with
learning and memory.
McFarland, David, ed. The Oxford Companion to Animal Behavior. Rev. and enlarged
ed. New York: Oxford University Press, 1987. Intended as a reference
guide, this comprehensive survey of behavior was written by a team
of internationally known biologists, psychologists, and neurobiologists. It
contains more than two hundred entries covering a variety of topics. Provides
a detailed summary of various forms of learning, including habituation
and sensitization. The index provides cross-references organized by
both subject and species lists.
Manning, Aubrey, and Marian Stamp Dawkins. An Introduction to Animal Behavior.
5th ed. New York: Cambridge University Press, 1998. A concise
handbook offering a light introduction to many general aspects of animal
behavior and learning. Provides a discussion on stimulus filtering, an
entire chapter on the physiological basis of behavior and motivation, and
a complete summary of various forms of learning. Well researched,
clearly written, and effectively illustrated.
Raven, Peter H., and George B. Johnson. Biology. 6th ed. Boston: McGrawHill, 2002. Chapter 56 of this general text on the science of biology offers
an excellent first introduction to the general concepts of ethology and
animal behavior. Includes a brief summary of learning and detailed coverage
of habituation, sensitization, and conditioning in Aplysia. A concise
summary, suggestions for additional reading, and review questions appear
at the end of each chapter.
Shepherd, Gordon Murray. Neurobiology. 3d ed. New York: Oxford University
Press, 1997. This somewhat advanced college-level volume on neurobiology
offers an in-depth account of the physiological basis of learning
and memory. A portion of chapter 30 is devoted to the neurological
changes associated with habituation and sensitization. Detailed diagrams,
data summaries, and complete literature reviews are provided.
Michael A. Steele
See also: Conditioning; Learning; Motivation; Pavlovian Conditioning; Reflexes.