Behavioral Responses to Stress
The stress response was initially described in the context of catastrophic events such as hemorrhage
, surgical injury, burns
, septic shock
, and intoxications. These events cause a reflex-like response that is nonspecific and depends on the importance of the deviation from homeostasis
. However, more common stressors such as daily life events do not act this way. The response depends on the evaluation
by the subject of the potential threat these factors represent. The transactional model of stress is therefore more appropriate than the stimulus–response of stress to describe what is occurring. Novelty, uncertainty, and the absence or loss of control are important dimensions in the evaluation process. An emotional response occurs if the event is recognized as discrepant, and it involves both physiological and behavioral adjustments.
Novelty occurs when the situation contains no or very few familiar elements. Subjects exposed to novelty explore the situation in order to identify potential sources of danger that need to be avoided and potentially interesting objects that can be safely approached. When novelty is too intense, fear
predominates over exploration, and escape attempts replace investigatory behavior. Uncertainty refers to the inability of predicting what is going to happen when the subject is exposed to an aversive or a potentially rewarding situation. In many cases, harmful or rewarding events do not happen all of a sudden. They are preceded by warning signals that can be used to predict their occurrence, via a process of classical (or Pavlovian) conditioning.
A tone that occurs before a painful electric shock
becomes a fear signal. Inversely, a bell that rings only when there is no electric shock is a safety signal. In an uncertain situation, the subject tries to find regularities in the succession of events to which he or she is exposed, so as to make the situation more predictable. The behavioral response to a fear signal is an anticipatory response that helps the individual to protect him- or herself from the danger. The response to a safety signal is a decrease in the tension and/or anxiety
induced by the possible occurrence of the harmful situation. Behavioral responses to a fear signal depend on the subject's proximity to the danger. When the subject is directly in contact with an uncontrollable threat, he or she usually tries to move away from the danger (active avoidance
). When the subject is at a close distance from the danger and cannot move away, he or she usually refrains from getting in contact with it (passive avoidance). This response is associated with immobility and freezing.
When the situation is rewarding rather than aversive, events that regularly precede the occurrence of the reward become positive conditioned stimuli or secondary reinforcers. They induce the development of conditioned behavioral responses that involve approach and other appetitive components of the normal behavioral response to the reward. If a secondary reinforcer is no longer followed by the occurrence of the expected reward, it induces a state of frustration that is characterized by agitation, aggression
, and other displacement activities (see below).
In situations that involve physical contact with congeners, behavioral responses to stress form part of the agonistic repertoire. Agonistic behavior refers to the complex of aggression, threat, appeasement, and avoidance behaviors that occurs during encounters between members of the same species. Attack is usually a highly ritualized behavior when it occurs in property-protective fights. The offender attacks its opponent at very specific parts of the body, such as the neck in rats, whereas the defender tries to protect these targets from bites
. When defeated, the defender adopts a submissive posture, exposing to the attacker more vulnerable body sites. Submission usually puts an end to the fight.
Confronted with a potentially harmful situation, the subject usually tries to do something in order to avoid the danger. Coping refers to the efforts undertaken to resolve the situation. Active and passive avoidance responses are examples of coping responses. Behavioral manifestations of coping vary according to the situation and the way the threat can be controlled. In laboratory animals, for instance, coping is typically studied by enabling the subjects to escape or avoid painful electric shocks when they emit a specific response such as a lever press, a wheel turn, or a move from one compartment to the other in a two-compartment cage. While animals in the escape/avoidance group are permitted to terminate electric shocks or delay their occurrence, animals in another group serve as yoked controls since they receive the same electric shocks as the previous animals, but their behavioral response has no effect on the occurrence and duration of electric shocks. As a further control, other animals are placed in the same apparatus as the animals in the other two groups, but they are never exposed to electric shocks.
Controllability can also be studied in human subjects by asking them to press a button, usually to terminate an intense noise. As in the animal experiment, the yoked group has no control over the noise. Helplessness refers to an individual's inability to control the situation when he or she has the opportunity to do so. When this happens after a previous experience of uncontrollable stress, it is referred to as learned helplessness
. Learned helplessness has cognitive, motivational, and emotional components. Coping attempts can be classified according to the strategy that is employed to confront the situation.
Active coping refers to all ways of dealing behaviorally directly with the situation, e.g., avoidance or attack. In human subjects, active coping can be cognitive (logical analysis and positive reappraisal) or behavioral. The latter case includes seeking guidance and support and taking concrete actions to deal directly with the situation or its aftermath. In an aversive context, cognitive coping comprises intrapsychic processes aimed at denying or minimizing the seriousness of the situation or its consequences, as well as accepting the situation as it is. Behavioral coping includes seeking alternative strategies to directly confronting the problem.
In general, active coping enables the subject to deal directly with the problem and is therefore characteristic of problem-oriented coping. In cases in which the problem cannot be directly dealt with, it is often preferable to engage in passive coping that focuses mainly on managing the emotions associated with it (emotion-oriented coping). In the case of passive coping, the behavioral activities that are normally elicited by the stimuli present in the situation are redirected toward more easily accessible targets.
A typical example is the redirected aggression that develops toward a subordinate when an animal in a social group is attacked by the dominant member of the group. Whereas redirected activities belong to the same behavioral repertoire as the thwarted behavioral activity, displacement activities belong to a different behavioral repertoire. This is the case for aggressive behavior
that is targeted toward peers or other objects in the environment in an animal that does not get the food it was expecting. A well-studied form of displacement activity is schedule-induced behavior. Schedule-induced behaviors, also known as adjunctive activities, typically occur when hungry animals are exposed to intermittent food rewards, delivered in very small amounts independently of the animals' behavior. Immediately after animals have eaten their allocated food, they vigorously engage in other activities depending on what is available in the situation. They drink exaggerated amounts of water if a drinking tube is accessible, attack a congener when present, or gnaw a piece of wood if available. To qualify as an adjunctive behavior, the behavioral activity must occur as an adjunct to the reinforcement schedule, not be directly involved in, or maintained by, the reinforcement contingency, and be persistent and excessive. Independently of the object toward which they are directed, adjunctive behaviors occur at a maximum rate immediately after the reinforcement and decrease in probability
when food deprivation is alleviated.
Interactions between Behavioral and
Physiological Components of the Stress Response
Compared to uncertainty and lack of control, predictability and controllability have deactivating effects on the physiological arousal evoked by the stress situation. In social conflict situations, activation of stress hormones is in general more pronounced in subordinate animals that behave defensively or passively than in offensive animals that remain active and become dominant. However, the social role is more important than the social status since dominance
is associated with a reduced arousal response only when dominant animals are recognized as such by their peers and do not need to reaffirm their status each time they are challenged by subdominant animals.
Schedule-induced polydipsia is associated with lowered plasma levels of stress hormones. This property is shared by other motor activities that involve sensory overloading from the mouth and tongue (e.g., licking or chewing) or the limbs (e.g., pacing). The de-arousal properties of coping behavior are not always that clear. Coping attempts are associated with increased activation of the sympathetic nervous system
, and they result in decreased physiological activation only when they have been successful and the threat is over.
The relationship between behavioral and physiological components of the stress responses is not unidirectional, with behavior influencing physiological responses, but truly bidirectional in the sense that the likelihood of a given behavioral response is dependent on the subject's initial physiology. Individuals with high activity of the sympathetic-adrenal-medullary axis are more likely to try to cope in an active way with a threat than individuals with a low activity of the sympathetic-adrenal-medullary axis. Inversely, individuals with a relatively higher activity of the hypothalamic-pituitary-adrenal axis
are more likely to resign and display helplessness than individuals with a normal or a lower activity of this axis.
Behavioral Sources of Stress
Most psychobiological theories of stress emphasize the previously described bidirectional relationships between the behavioral and physiological components of stress in response to stressors. However, they do not necessarily account for the powerful influence of the subject's own behavior on the probability of occurrence of the stressful situation itself. A typical example for understanding this point is represented by the type A behavior pattern (TABP).
TABP is defined as an action–emotion complex that individuals use to confront challenges. The complex involves behavioral dispositions such as aggressiveness, competitiveness, and impatience; specific behaviors such as muscle tenseness, alertness, rapid and emphatic vocal stylistics, and accelerated pace of activities; and emotional responses such as irritation, covert hostility
, and above-average potential for anger
. Type B individuals are characterized by the relative absence of type A behaviors and confront every challenge with placid nonchalance. Type A individuals have a higher risk of developing coronary heart disease
than type B individuals. The deleterious effects of type A behavior appear to be associated with a higher physiological reactivity to external demands, especially when there are elements of competition. These findings corroborate the previously mentioned influences of behavioral factors on the physiological response to stress. In accordance with the bidirectional nature of hormone– behavior relationships, type A behavior does not occur at will. It is determined at least in part by biological factors and autonomic hyperactivity
. All this makes type A behavior a typical psychobiological construct. However, this concept is not sufficient to account for what happens in the real world. Type A individuals actually create their own problems by putting themselves in situations of competition and taking all steps to transform the events they are confronted with in challenges that need to be met in a more hostile way than their peers would be inclined to do.
A similar situation occurs in sensation-seeking individuals. There is evidence that subjects with this personality
trait display enhanced responses to novelty and danger. The probability for a given individual to be a sensation seeker is determined by innate and experiential factors. However, what is characteristic of sensation seekers is their strong preference for sensation-inducing situations rather than their increased response to such situations. In sum, individuals are not passively exposed to stress; they actually create their own stress by the way they behave and perceive their environment.
the Following Entrys
Aggressive Behavior; Behavior Therapy
; Defensive Behaviors
; Evolutionary Origins and Functions of the Stress Response
; Health Behavior and Stress
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McFarland, D. J. (ed.) (1987). The Oxford companion to animal behaviour. Oxford, UK: Oxford University Press.
Ursin, H. and Eriksen, H. R. (2004). The cognitive activation theory of stress. Psychoneuroendocrinology 29, 567–592.
Appetitive stimulus A stimulus that induces approach and exploratory responses.
Aversive stimulus A stimulus that induces avoidance and escape responses.
Behavioral sequence A succession of appetitive and consummatory components. The appetitive sequence enables the subject to approach the goal object. Upon reaching the goal, appetitive behavior normally ceases and gives way to consummatory behavior that enables the subject to appropriate its goal.