Reflexive Organization

Much of a dog's behavior is under the reflexive control of involuntary mechanisms. As discussed in Chapter 2, neonatal puppies exhibit a great variety of reflexes that are predominately geared to maintaining contact with the mother to secure basic survival needs. These early neonatal reflexes gradually disappear and are replaced by more centrally controlled behaviors as puppies mature. Neonatal reflexive behavior has been carefully studied and cataloged (Fox, 1964). Understanding how the body's reflexes work was the primary emphasis of Sherrington's (1906) experimental work. He discovered that many of the dog's apparently voluntary behaviors were to some extent under the control of involuntary reflexive mechanisms. A dog's scratch reflex, for example, could be elicited by applying an electrical "itch" to its skin. Although mechanical and stereotypic, the scratch response was organized and well directed toward the source of the itch. What makes this noteworthy is that the dogs involved were decerebrate, having undergone previous surgeries to cut nervous pathways going to (afferent) or leaving (efferent) the brain. Other surprising abilities of decere-brate dogs included unsteady treadmill walking, withdrawal and crossed extensor reflexes to pain (the stimulated leg flexes while the opposing leg extends in order to push away from the noxious stimulus), and differential gustatory responses (a swallow reflex was elicited by milk whereas noxious substances were expelled).

The Russian physiologist Ivan Sechenov, the father of reflexology, made several discoveries about reflexive behavior that anticipated the findings of Sherrington. The following is a description of one of his famous experiments with frogs:

Cut off the head of a frog and place the decapitated animal on the table. For a few seconds it seems to be completely paralyzed; but before a minute has passed you see that it has recovered and assumed the posture peculiar to the frog when in a state of rest on dry land: its hind legs are tucked under it and it supports itself on the front legs like a dog. If you leave it alone, or to be more precise, if you do not touch its skin, it will remain motionless for a very long time. But the moment you touch its skin, it starts and then resumes its quiet posture. Pinch it somewhat stronger and it will, in all likelihood, jump as if trying to escape from pain. (1863/1965:6-7)

The above reflex actions (and many others) do not require voluntary effort but result from the wiring of nervous connections between sensory receptors, motor neurons, and interneurons (a simple neural relay system) located in the brain stem and spinal cord.

Sherrington divided reflexive behavior into two broad categories: phasic and tonic. Phasic reflexes are those that occur quickly with a brief response, such as the patellar reflex (knee jerk). Tonic reflexes are those that involve sustained adjustments and equilibrating efforts over flexor/extensor dominance. An interesting example of tonic reflex action is thigmotaxis. Two instances of thigmotaxis can be readily observed in dogs. Fearful dogs tend to lean against their owner's body or may lay down on the ground as though pushing into it. This reaction is called positive thigmotaxis and is a common tonic reflex in fearful animals. Another example involves a dog's reaction to opposing pressure or force. Whenever a dog's body is pushed or pulled, the dog tends to react reflexively by responding in an opposing direction to the direction of the force applied to its body. Oppositional reflexes enable dogs to maintain physical equilibrium or to sustain a course of action when exposed to opposition. An especially common instance of this effect is seen when a dog pulls during walks, a tendency that is evoked by the owner's habit of pulling against the dog's forward movement. Such reflexive oppositional reactions explain why most trainers recommend that the leash be held in a slack manner and that the dog be corrected with a snapping action rather than a slow continuous pull.

Sherrington described several factors influencing the elicitation of reflexive action:

Threshold refers to the minimum stimulus intensity sufficient to elicit the reflex. A high threshold means that a relatively strong stimulus is needed to elicit a response, whereas a low threshold suggests that a relatively weak stimulus is needed to elicit a response. Altering response thresholds is an important part of effective behavior modification, especially involving emotional systems under the regulation of reflexive mechanisms.

Latency refers to the duration from the moment of stimulation to the onset of the reflexive action. Latency depends on the intensity of the stimulus involved and on the readiness of the animal to respond.

Irradiation refers to the tendency of an especially strong stimulus to elicit a generalized reaction extending to surrounding or associated neural systems.

Reciprocal inhibition neural systems refers to the tendency of elicited muscle actions to inhibit the actions of an opposite type. The elicitation of muscle reflexes involves three possible actions: flexion, extension, or a tonic combination of the two. Stimulating a group of muscles to flex causes the simultaneous inhibition of opposing extensor muscles. The concept of reciprocal inhibition was later adopted by Wolpe (1958) to describe the effect of counterconditioning and the process of systematic desensitization. Wolpe argued that relaxation/appetite and anxiety/fear are mutually exclusive affects that regulate each other through a mechanism of reciprocal in-hibition—that is dogs cannot simultaneously feel anxious while relaxed or fearful while eating. The third characteristic of reciprocal inhibition (flexor/extensor tonic equilibrium) is analogous to situations in which opposing emotional alternatives are held in a stasis of conflict between the available options.

Fatigue occurs when repeated elicitation of a reflex action causes it to weaken or habituate. Habituation is the most basic form of learning observed in all animals from humans to sea snails.

Many basic biological functions are under the control of reflexive mechanisms. Although some reflexes can be influenced by voluntary efforts, most reflexes occur automatically, given the presence of a sufficiently salient stimulus. For instance, one can resist and possibly inhibit or slow the blink reflex elicited by touching the eyelashes, but it is much more difficult (if not impossible) to control pupillary constriction in the presence of bright light, stop salivation in the presence of food, or inhibit heart rate acceleration while in a fear-eliciting situation. Pavlov (1927) discovered that these sorts of behavioral and physiological events could be brought under the control of normally neutral stimuli through a conditioning process. The basic procedure was carried out by pairing the sound of a bell with the presentation of food. After a number of such contiguous pairings between the neutral stimulus (bell) and the unconditioned stimulus (food), the previously neutral bell becomes a conditioned stimulus that is able to elicit a conditioned response—that is, a response that is similar to the original or unconditioned response. As is discussed in Chapter 6, classical conditioning is an important tool in a trainer's armamentarium for managing and controlling dog behavior.

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