Science: Feeling and Hearing

Sensory perception in animals is a major preoccupation in the psychology laboratories of the University of Rochester. There young John Warkentin, by recording the eye movements of animals placed inside a striped, revolving cylinder, has tested visual acuity in such difficult subjects as snakes, frogs, toads, turtles, alligators, gophers, Gila monsters. Some months ago Rochester’s psychology department chairman, Dr. Leonard Carmichael, left to become president of Tufts College. He was replaced by trim, twinkly, soft-spoken Elmer Augustine Kurtz Culler, formerly of the University of Illinois, who has made profound studies of the “conditioned response” and whose specialty is the mechanism of hearing in mammals. By last week Dr. Culler had finished installing his battery of gadgets and he was able to show Rochester newshawks how he determines the threshold of hearing in a dog, cat or guinea pig.

The animal is placed inside a big squirrel cage which revolves when the creature runs. A faint musical tone sounds, followed after a short interval by a mild electric shock administered through the bars of the cage. If the animal runs the turning of the cage switches off the current, thus sparing the subject further shock. After a few experiences the dog, cat or guinea pig learns to avoid shock by running the moment it hears the musical signal. When this conditioned response is set up Dr. Culler can easily find the threshold of hearing by steadily diminishing the loudness of the signal until the animal no longer responds by running. Dogs, which hear best, have about the same acuity as human beings.

Irrespective of their individual hearing abilities, dogs learn most quickly how to avoid shock and guinea pigs are slowest. The scientist found one genius of a guinea pig, however, which learned what to do after only one experience.

One of Dr. Culler’s research programs has resulted in a tentative explanation of a bizarre phenomenon known as the “XRay Effect.” Several clinicians had noticed that when human heads were exposed to X-rays, a temporary improvement in hearing frequently occurred. Dr. Culler confirmed and explained this phenomenon. Studying X-rayed dogs, he found that the irradiation weakened the pituitary control of the pancreas, which thereupon released more insulin in the blood. The insulin excess lowered the blood’s sugar content, which in turn lowered the density and viscosity of the fluids in the hearing mechanism of the inner ear. The ear thereby became more susceptible to sound vibrations.

Dr. Culler also pointed out last week that diabetic humans find they can hear better after a dose of insulin has reduced their blood-sugar level. He also declared that normal people hear less well after their sugar level has been raised by “a good square meal.” This would indicate that, for best reception, speeches should be made before banquets instead of afterward.