Normally dogs snatch at food; elephants reach out their trunks for it. A man will pull his hand away from a hot plate. These are examples of unconditioned reflexes, fully developed in infancy. They constitute the equipment with which the animal faces life, according to the behaviorists.* By modifying the conditions, the simple reflexes may be changed, becoming more complicated, or conditioned. The process of changing an unconditioned reflex into a conditioned reflex was clearly demonstrated to an audience of psychiatrists at the Academy of Medicine last week, in a cinema entitled "The Mechanics of the Brain."
The cinema showed dogs which dripped saliva at the sound of a bell, monkeys which marathoned to the food box at the sight of a red card, children who opened hungry mouths when their wrists were pressed. These are examples of conditioned reflexes and upon this conditioning is based the difference between the lower and the higher animals, including man.
The unconditioned reflex is the simplest nervous reaction. A dog will smell food and turn in its direction. Nature believes in preparedness and the dog will secrete saliva as he goes for the food. Only the lower parts of the brain are concerned in this reaction. But, if a bell is rung every time the food appears, there will come a time when the dog will secrete saliva at the sound of the bell when there is no food in sight.
The simple reflex has been conditioned by the bell; the dog has associated the food with the sound; the power house of the upper brain has gone into action, and the intelligent animal now reacts to an idea. This is the learning mechanism in its elementary form. If the upper brain is now removed, the learned reaction will be lost.
Not only can animals be taught to associate widely different stimuli, but they can be taught to discriminate. Example:
Old Lady, wise ape, was presented repeatedly and alternately with a red card, and with a blue card. With the red card came, always, food in a food box. With the blue card came the food box but no food. After a while, the food box was removed to a distant corner. Red and blue cards kept flashing before Old Lady's eyes. When the blue card flashed, Old Lady gazed at it in polite boredom and went on quietly with her toilet. They couldn't fool her. But when the blue card disappeared and the red card showed, Old Lady's eyes gleamed. She swung herself from her perch, rushed down the ladder with unladylike haste and made for the food box in the corner.
Here is the rejection of one idea and the acceptance of another; a more complicated instance of learning.
The evolution of the animal depends on the development of the upper brain: the greater the development the more complicated the conditioned reflexes become. The ability to learn by experience, which is simply a matter of conditioning the reflexes, increases; the animal can adjust to ever more varied environments. Man has the most intricately convoluted upper brain of the whole animal kingdom and can therefore adapt himself to a wide range of conditions.