Conditioned reflexes and habit formation / by W. Horsley Gantt.

  • W. Horsley Gantt
Date:
[1932?]
Catalogue details

Licence: In copyright

Credit: Conditioned reflexes and habit formation / by W. Horsley Gantt. Source: Wellcome Collection.

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    food centre being of more physiologic importance to the animal than the destructive pain stimulus. No agent is really indifferent, because even though it may not natur¬ ally call forth any reaction, and though it may be new for the dog and have no performed connexions, it always provokes the orienting or investigating reflex. Then the conditioned stimulus must precede the unconditioned. This was thought to be essential until recently, when Pavlov showed that the conditioned stimulus following the unconditioned may eventually acquire a slight con¬ ditioned value. However, this may cause a hypnotic state in the animal. Formation of Conditioned Reflex What is the mechanism of the formation of the con¬ ditioned reflex? Not simply the repetition alone. Pavlov explains it by saying that the excited food centre draws all simultaneous stimuli to itself, and so a path is made in the cortex between all changes in the milieu and the excited centre. Then the organism must be in the proper state ; for example, we cannot form a conditioned food reflex if the animal has just satiated itself. Now we come to the formation of the conditioned reflexes. The conditioned stimulus—that is, any change in the internal or external milieu of the dog—must be repeated one or more times with the unconditioned stimulus. The number of repetitions varies with the species, the intelligence, age, etc. In fish it may be necessary to repeat the laboratory stimulus three hundred times to form the conditioned reflex, for the dog ten to fifty times, and in a child four to ten times. Old animals elaborate conditioned reflexes very slowly or not at all. An idiot may not form the conditioned reflex as quickly as a fish. These cortical reflexes about which we are speaking are continually coming into existence, fluctuating in intensity, diminishing, increasing, and disappearing— that is, they are conditional. This brings us to the question of inhibition. Indirect Inhibition The conditioned reflex may be subject to two kinds of inhibition. One sort is that described by Sherrington, and is analogous to spinal inhibition. It occurs when two centres are in activity at the same time ; a conflict arises ' for the dominance of the field. As the activity is in a different centre from the one with which we are working, Pavlov calls it external or indirect inhibition. Examples are occurring every minute of our lives. We have given
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