Chapter Outline

Chapter Outline

1. THE INSTINCTIVE BASIS OF BEHAVIOR

   Lorenz proposed that instinctive systems promote adaptation to the environment. Moreover, the ability to learn is programmed into species by their evolutionary histories. Therefore, the ability to learn is an innate characteristic.

   1. The Search for Knowledge: Lorenz emphasized that organisms are "built" through evolution to process environmental information that is important for their survival.

   2. The Interaction of Energy and Environment: Lorenz and his colleague Tinbergen spent many years observing animal behavior in natural habitats. From these observations, Lorenz developed an energy model of instinctive behavior.

      1. Energy Model

         Lorenz proposed action-specific energy as the internal force that accumulates within the organism and provides the motivation for behavior. It is action-specific in the sense that each behavior (action) requires its own specific energy. As the energy builds, it is prevented from being released by an innate releasing mechanism (IRM). The increasing pressure stimulates appetitive behavior and energizes overall behavior, increasing the likelihood that an animal will encounter an environment that contains a sign stimulus. This stimulus is a "trigger" that releases the accumulated energy. The result is a fixed action pattern, which might be considered an instinctive behavior.

      2. Environmental Release

         The releaser (sign stimulus) for a fixed action pattern may be simple or complex. The probability that a fixed action pattern will occur depends upon several factors, including (1) the intensity of the sign stimulus and (2) the accumulated level of action-specific energy.

      3. Hierarchical System

         Although some simple behaviors involve only a few movements, many "higher-level" instincts, such as reproduction, require many fixed action patterns. In such cases, Lorenz assumed that energy, in the form of neural/hormonal events, builds up at this high level, and is released to lower levels. The specific fixed action pattern that occurs at any moment depends upon which sign stimulus is present. Presumably, separate brain areas control each action. Thus, complicated sequences of behaviors, such as in reproduction, are controlled by both brain and environmental events in a coordinated fashion.

      4. Conflicting Motives

         Because separate fixed action patterns have their own action-specific energy and sign stimuli, conflicts can arise when two opposing systems are triggered by the two sign stimuli. In this case, energy may spill over and release some other behavior, called displacement.

   3. The Importance of Experience: Lorenz recognized that instinctive behavior is not necessarily rigid and unmodifiable. He suggested that experience (learning) can alter the form of appetitive behaviors, and/or the sensitivity of the IRM to the sign stimulus. Although there are many parallels between Lorenz's energy model and the way environmental cues can release behaviors, the model is not a perfect one of how brain controls behavior.

2. HABITUATION AND SENSITIZATION

   Habituation and sensitization are two fundamental learning processes. In each case, animals change their reactions to a stimulus with repeated stimulation. Habituation is defined as a decrease in responsiveness to a stimulus, as is seen in ingestional neophobia (decreased avoidance of a novel food over time). Sensitization refers to an increase in reactivity to the stimulus.

   1. The Nature of Habituation and Sensitization: Groves and Thompson suggest that habituation involves decreased reactivity of innate reflexes, so that with repeated stimulation, the animal's nervous system reacts less to the stimulus. Conversely, sensitization may occur because of increasing nervous activity with repeated exposures to the particular stimulus and perhaps to all stimuli.

   2. The Conditions Affecting Habituation and Sensitization: Not only are habituation and sensitization different behaviorally, they differ in how various conditions affect them. Some of these factors include (1) the intensity of the stimulus and (2) the consistency of the stimulus (e.g., whether its shape changes from stimulation to stimulation). Both habituation and sensitization can be transient phenomena. If habituation lasts over a long time, it suggests some learning has occurred. Sensitization appears to result from an increase in overall arousal level.

   3. Dishabituation: Support for increased arousal as a cause of sensitization is the phenomenon of dishabituation, defined as the recovery of an habituated response as a result of encountering a sensitizing stimulus. Thus, even though an animal has habituated to a stimulus, some other arousing stimulus can reinstate the response to the habituated stimulus. It is adaptive for our nervous systems to habituate to irrelevant stimulation. It is also adaptive to be more alert to our environment when some sensitizing (arousing) stimulus appears.

3. OPPONENT-PROCESS THEORY

   Solomon and Corbit proposed an opponent-process theory of emotion to describe how we react to emotional stimuli, and how our responses change with repeated exposure to the stimuli.

   1. Our Initial Reaction: An emotional stimulus can elicit a primary emotional response (A state), which then instigates an opposite emotional response (B state). The A state may be pleasant (thus evoking an unpleasant B state), or it may be unpleasant (thus evoking a pleasant B state). The intensity of A is tied to the intensity of the stimulus, and a given stimulus will always produce the same A state. The intensity of B is determined by the intensity of A. Compared to the A state, B is initially less intense than A, is sluggish in intensifying, and is also sluggish in terminating. The overall emotional response to a stimulus is the summation of A and B over time.

   2. The Intensification of the Opponent B State: The theory suggests that repeated stimulation (and thus repeated A states) causes changes in B that include its (1) more rapid onset, (2) greater intensity, and (3) slower offset. This may help explain tolerance and withdrawal in drug addiction. Tolerance involves reduced reactivity to a drug with repeated exposure to the drug. Withdrawal refers to the adjustment of the body and a drug craving when the drug is not present. The development of tolerance is the weakening of the A state (because B increases). Withdrawal is the intensification of the B state, especially when no drug is present.

   3. The Addictive Process: Addiction does not always develop in people who use drugs. But when it does, Solomon says it is because addicts recognize that drug abstinence produces withdrawal symptoms (B state). Thus addicts seek the drug (which increases the A state) simply to overcome the unpleasant feelings of withdrawal.

   4. The Influence of Other Aversive Events: The theory may help explain why addictions are difficult to cure. The addict's B state is a generalized discomfort. Thus, any other situation that arouses a similar general discomfort might motivate the addict to seek out the drug again to decrease the discomfort.

   5. The Search for Pleasure: Addiction to most drugs is based on the drug producing a pleasant A state, which is followed by an unpleasant B (withdrawal) state. But some behaviors, such as thrill-seeking, may represent a situation that produces an unpleasant A state with a pleasant B state that intensifies with repeated stimulation.