Conditioning
For many years the measurement of hearing in small children had been a serious challenge. Hearing is the most important of our sense organs, the basis of language and communication. I used to tell my students in Medical School that we remember learning to read and write, but we do not remember learning to speak, which is much more complicated. Reading and writing is simply a representation of our speech with symbols. Learning to speak is a much more difficult task for our nervous system, a task that starts when we are born. The period of time from two months to 30 months of age is the most intense activity in acquiring language.
In the old days most of the hearing tests in young children could only be done by conditioning.
There are two types of conditioning, the classical, or pavlovian type, developed by Ivan Pavlov in 1927, and the instrumental type, developed by Edward Thorndike and extensively revised by B. F. Skinner. In Pavlov’s classical experiment the dogs were conditioned to salivate when they heard the sound of a bell. Before the conditioning they would only do that when they saw, or smelled, food. The capacity for salivation, however, was something that the animal already possessed before the conditioning sessions.
In instrumental conditioning the animal learns. It jumps from one side of the Skinner box to the other because it learned that it will get a reward for that behavior, or will be punished for not doing it. This concept led to behaviorism, a concept that all the things we learn may have resulted from some type of conditioning.
Instrumental conditioning is still used today in testing the hearing of two to three-year-old children, using simple toys the child can move only after hearing a sound. Complicated systems do not work. Dr. Margaret Dix, in England, designed a system that she named peep show, an interesting device that showed pictures from children’s books, and in order to move the slides the child had to hear a sound. But the peep show did not work well when the child was not interested in the pictures. Here in São Paulo an audiologist decided to use a car race track. The child controlled the button to start the car, but it only worked after the sound was presented. The children wanted to play with the cars and the test irritated them enormously. So we had to go back to very simple toys.
During my training years pavlovian conditioning was also used. It was called psychogalvanometry, or electrodermic audiometry. The principle was similar to the lie detector, the system measured the skin resistance between two surface electrodes. This resistance is reduced with the activity of the sweat glands. Sound does not change the skin resistance, as lies do, so we had to condition the response by stimulating the child with subliminal electrical shocks and simultaneous sounds (the shocks had to be subliminal, otherwise the child would start to cry and we lost the chance to make the test). After a few simultaneous electrical and sound stimuli we would use sound only and if we had a response it meant that the child was conditioned. Then we would gradually reduce the intensities to find our thresholds.
I tested many children with psychogalvanometry. It worked well, although it was very time consuming.
It is definitely easier, and much more precise, to use electrocochleography, brainstem audiometry and otoacoustic emissions. But all of these tests are relatively recent. And sometimes behavioral tests give us important clinical information. One of the good things of the new techniques is that we can now perform screening tests in newborn babies, enabling us to detect deafness much sooner.
There is a classical joke regarding instrumental conditioning. It is about a mouse, in a Harvard University laboratory, telling another:
“I succeeded in conditioning Professor Skinner. I press this bar and he gives me water.”
In the old days most of the hearing tests in young children could only be done by conditioning.
There are two types of conditioning, the classical, or pavlovian type, developed by Ivan Pavlov in 1927, and the instrumental type, developed by Edward Thorndike and extensively revised by B. F. Skinner. In Pavlov’s classical experiment the dogs were conditioned to salivate when they heard the sound of a bell. Before the conditioning they would only do that when they saw, or smelled, food. The capacity for salivation, however, was something that the animal already possessed before the conditioning sessions.
In instrumental conditioning the animal learns. It jumps from one side of the Skinner box to the other because it learned that it will get a reward for that behavior, or will be punished for not doing it. This concept led to behaviorism, a concept that all the things we learn may have resulted from some type of conditioning.
Instrumental conditioning is still used today in testing the hearing of two to three-year-old children, using simple toys the child can move only after hearing a sound. Complicated systems do not work. Dr. Margaret Dix, in England, designed a system that she named peep show, an interesting device that showed pictures from children’s books, and in order to move the slides the child had to hear a sound. But the peep show did not work well when the child was not interested in the pictures. Here in São Paulo an audiologist decided to use a car race track. The child controlled the button to start the car, but it only worked after the sound was presented. The children wanted to play with the cars and the test irritated them enormously. So we had to go back to very simple toys.
During my training years pavlovian conditioning was also used. It was called psychogalvanometry, or electrodermic audiometry. The principle was similar to the lie detector, the system measured the skin resistance between two surface electrodes. This resistance is reduced with the activity of the sweat glands. Sound does not change the skin resistance, as lies do, so we had to condition the response by stimulating the child with subliminal electrical shocks and simultaneous sounds (the shocks had to be subliminal, otherwise the child would start to cry and we lost the chance to make the test). After a few simultaneous electrical and sound stimuli we would use sound only and if we had a response it meant that the child was conditioned. Then we would gradually reduce the intensities to find our thresholds.
I tested many children with psychogalvanometry. It worked well, although it was very time consuming.
It is definitely easier, and much more precise, to use electrocochleography, brainstem audiometry and otoacoustic emissions. But all of these tests are relatively recent. And sometimes behavioral tests give us important clinical information. One of the good things of the new techniques is that we can now perform screening tests in newborn babies, enabling us to detect deafness much sooner.
There is a classical joke regarding instrumental conditioning. It is about a mouse, in a Harvard University laboratory, telling another:
“I succeeded in conditioning Professor Skinner. I press this bar and he gives me water.”
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