A great deal of experimental attention has been focused on the etiology of abnormal behavior and neurosis in animals (Patton, 1951; Broadhurst, 1961). The term neurosis is used here in a narrow sense, not to be mistaken for the condition described in human psychiatry, although parallels do exist between human and animal neuroses. To limit confusion, a working definition of neurosis is needed. In the Oxford Companion to the Mind, Gregory defines neurosis as a maladaptive habit: "Neurosis is a habit that is either maladaptive in some obvious respect and/or distressing, yet more or less fixed and resistant to modification through the normal process of learning" (1987:549). The value of this definition is its conceptualization of neurotic behavior in terms of habit and learning. It falls short of being a complete definition because it fails to emphasize the role of emotional disturbance in the etiology of neurotic habits. In general, neuroses result from underlying emotional disturbances collectively impacting on various behavioral, cognitive, and somatic systems. Therefore, the definition is supplemented to include a recognition of the emotional aspect of neurotogenesis: A neurosis is an emotionally maladaptive and persistent habit or compulsion that resists modification through normal processes of learning.
Neurotic disturbances are most likely to occur in situations where an animal's ability to predict and control the environment is rendered by varying degrees independent of what actually happens (Mineka and Kihlstrom, 1978). Like many human neu rotics, neurotic animals seem to be "possessed by" a negative expectation that causes them to "believe" that what they do or intend to do will have little discernible impact on what occurs. In extreme cases, the effect can be described as a generalized state of powerlessness or futility, or what Seligman has called learned helplessness. Knowing that neuroses are precipitated by cognitive or behavioral failures to adequately predict and control significant events, it is not surprising to find that most neurotic disorders present comor-bidly with chronic anxiety (a generalized emotional state associated with inadequate prediction) or depression (a generalized emotional state associated with inadequate control).
The laboratory induction of disturbed behavior is referred to as experimental neurosis. Most experimental neurosis studies have been based on the prevailing assumption that neurotic behavior disorders are of a learned origin. Several animal models based on this premise have been developed (Keehn, 1986), with the aim of clarifying the etiology and treatment of neurotically disorganized behavior. The discovery of experimental neurosis is credited to Pavlov's laboratory, in particular, to the Russian researchers Yerofeyeva and Shenger-Krestovnikova, who observed that some dogs when confronted with certain experimental arrangements exhibited dramatic disturbances of previously conditioned behavior. The dogs also exhibited a variety of collateral deviations from the norm both inside and outside the experimental setting. Pavlov considered these disturbances to be of a neurotic origin, that is, elaborations of internal conflict arising from the dysfunctional collision of excitatory and inhibitory processes.
The first example of experimental neurosis produced in Pavlov's laboratory was obtained by Yerofeyeva. In this instance, a dog was shocked and then presented with food, which the dog was forced to eat if necessary. The intensity of shock was gradually increased over several conditioning trials, until it was strong enough to cause "severe burning and mechanical destruction of the skin." Following conditioning, the dog showed no signs of defensive behavior or autonomic changes in res piration or heart rate, even when stimulated with the maximum level of current. The experimenters observed that the dog simply salivated and approached the food to eat when shock was turned on. This state of affairs persisted for several months, until the site of stimulation was moved to other places on the dog's skin. When the number of sites increased to a certain saturation point, the previously conditioned response to shock drastically changed. The dog now exhibited an explosive defensive reaction whenever and wherever the shock stimulus was delivered. Even electrical stimulation of the original location resulted in uncontrollable defensive behavior, with no sign of appetitive interest or salivation. The conditioned alimentary reflex to shock was permanently lost, and the previously calm dog became extremely agitated and hyperactive.
Pavlov's workers employed many other experimental methods to induce neurosis (Cook, 1939; Kurstin, 1968). The procedures included the following: (1) The repeated presentation of a conditioned stimulus (CS) that simultaneously elicits both an excitatory and a competing inhibitory reflex. Presumably, the effect is a collision of opposing emotional intentions, producing motivational conflict. (2) Difficult discrimination tasks in which similar stimuli control mutually incompatible responses (e.g., the experiment by Shenger-Krestovnikova discussed below). (3) Exceptionally long presentations of conditioned stimuli before being followed by unconditioned stimulus (US) reinforcement of excitatory conditioned reflexes—that is, disturbances produced by overstrain of anticipatory processes. Petrova (Pavlov, 1927/1960), for example, trained two dogs (one tending toward excitability and the other a more inhibited type) to respond to six different stimuli as salivary conditioned stimuli. Initially, the interstimulus interval between the CS and US was very brief, but as training proceeded this interval gradually increased by 5 seconds daily. Disturbances (in the excitable dog) began to appear after 2-minute intervals were reached. Dramatic disturbances of behavior were observed with 3-minute delays between the CS and US. Pavlov writes that the excitable dog "became quite crazy, unceasingly and violently moving all parts of its body, howling, barking, and squealing intolerably. All this was accompanied by an unceasing flow of saliva, so that although the secretion increased during the action of the conditioned stimuli all traces of the delay completely disappear" (1927/1960:294). The more inhibited dog was able to cope with the delay without signs of behavioral disturbance. (4) An abrupt shift from an excitatory stimulus to an inhibitory one and vice versa. (5) Unpredictable expectancy reversals—for example, a CS that had been previously associated with food is followed by shock instead. (6) The occurrence of any intense, unusual, or traumatic stimulation—for example, the effect of the Leningrad flood reported by Pavlov or the laboratory dog fight reported by Gantt (see the following section on post-traumatic stress disorder).
The disturbances produced by the foregoing procedures can be divided into three general categories: (1) disturbances of normal learning abilities (e.g., some previously learned habit is no longer exhibited, loss of conditioned inhibition, or an impairment of an animal's ability to reacquire the lost habit or association); (2) autonomic disturbances (e.g., cardiac, respiratory, sexual, and secretory changes), and excessive emotional displays, like fear and aggression; and (3) elaboration and generalization of unusual behavioral changes, both inside and outside of the experimental context (e.g., increased shyness and aggressiveness toward other dogs and people as well as long-term autonomic disturbances). Hebb (1947) argued that many of these symptoms of neurosis could actually be viewed as adaptive species-typical responses to traumatic stimulation and nervous overstrain. He argued that true neurotic disturbance led to persistent learning deficits (e.g., a failure to perform acquired discriminations).
Shenger-Krestovnikova induced neurotic symptoms by exposing a harnessed dog to a series of difficult visual discriminations. In her famous experiment, she alternately presented the dog with a circle and an ellipse. The shapes were projected onto a screen located directly in front of the dog. The appearance of the circular shape was immedi ately followed by the presentation of food. After several trials, the circle became a conditioned excitatory stimulus (CS+) capable of eliciting salivation. Next, the elliptical shape was introduced. On each occasion that the ellipse appeared, food was withheld. Gradually, the ellipse became a conditioned inhibitory stimulus (CS-) predicting the absence of food. As the experiment proceeded, the ellipse was progressively modified, so that it gradually approximated the shape of a circle. At a critical point where the susceptible dog could no longer consistently differentiate the circle from the ellipse, it was either seized by hyperactive reactivity or despondency. The response exhibited depended on the dog's temperament and predisposition. Pavlov described the disorganized behavior of a dog exposed to this experimental arrangement:
After three weeks of work upon this differentiation not only did the discrimination fail to improve, but it became considerably worse, and finally disappeared altogether. At the same time the whole behaviour of the animal underwent an abrupt change. The hitherto quiet dog began to squeal in its stand, kept wriggling about, tore off with its teeth the apparatus for mechanical stimulation of the skin, and bit through the tubes connecting the animal's room with the observer, a behaviour which never happened before. On being taken into the experimental room the dog now barked violently, which was also contrary to its usual custom; in short it presented all the symptoms of a condition of acute neurosis. (1927/1960:291)
A few dogs exhibited cataleptic immobility. This behavior was often associated with the refusal of food and with aggressiveness toward familiar persons with whom the dogs were previously friendly. Some dogs moved from a stupor into a state of furious rage. Others exhibited a cyclic, bipolar alternation of intense excitability followed by pronounced inhibition. Astrup (1965) noted that such symptoms are similar to those exhibited by human psychiatric patients with bipolar mood disorders.
Thomas and DeWald (1977) performed a series of experiments employing Shenger-Krestovnikova's procedure with cats. The cats were exposed to light and tone discrimina tion tasks in which the CS+ and CS— became progressively similar. They were trained under both classical and instrumental paradigms. Special controls and methods of quantification were also added to obtain more objective data of experimental neurosis. Their results are consistent with the aforementioned results reported by Pavlov, both in terms of dysfunctional learning symptoms (especially nonresponding) and collateral behavioral disturbances:
All subjects in both paradigms [i.e., classical and instrumental] showed a very similar sequence of collateral behavior concomitant with the interruption of responding. As a rule subjects discontinued responding and suddenly became aggressive and attempted to escape. Many attacked objects within the chamber, such as the house light. The degree of emotionality may be inferred from the urination and defecation that often occurred in the chamber only during the specific periods of nonresponding. A number of animals developed diarrhea after at least two days of experimental neurosis. The initial symptoms, then, may be characterized as severe agitation. However, over a period of several successive days in the apparatus, the agitation abated and generally yielded to depression. Animals sat or lay immobile with their shoulders rigidly hunched in a distinctively depressive posture that is characteristic of experimental neurosis. Some animals crouched as if to urinate and remained in this position for long periods of time. ... Three animals refused food when the food magazine was operated. The other three animals approached the food very lethargically and often waited for several minutes after the food was presented before approaching and eating. (1977:222)
Pavlov found that not all dogs were equally susceptible to develop neurotic symptoms. A dog's degree of vulnerability to neurosis was dependent on its temperament. Pavlov divided dogs into four broad types, two of which he believed were particularly prone to the elaboration of neurotic disturbances. The temperament types that he recognized are (1) sanguine: very active, socially demonstrative and flexible; (2) phlegmatic: less active, socially retiring and stable; (3) choleric: highly unstable, manic, and prone to develop neuroses involving excitatory processes; and (4) melancholic, low activity, socially withdrawn and susceptible to neuroses involving inhibitory processes. Dogs with weak, unbalanced temperaments (choleric and melancholic) were found to be more easily stressed and at greater risk of developing learning and behavior disturbances than sanguine and phlegmatic dogs possessing balanced and flexible temperaments (Fig. 9.1). Pavlov believed that dogs were at an increased risk of developing neuroses during puberty and following castration (Windholz, 1994). Surprisingly, young puppies were found to be the least affected by adverse conditioning. Combining these basic temperament types with Eysenck's introversion (socially withdrawn, reserved, and passive) and extraversion (socially outgoing, impulsive, and active) dimensions (see Gray, 1971) produces a number of interactions of interest for understanding some aspects of dog behavior (Fig. 9.2). Traits on the upper half of Fig. 9.2 show signs of progressive neuroticism, with dysthymic (Eysenck's terms) instability affecting melancholic introverts (introverted neuroti-cism), whereas hystericopsychopathic instabilities present in the case of choleric extraverts (extraverted neuroticism) (see Gray, 1971).
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