Abstract
The purpose of these experiments are to establish the conditioned pupillary reflex in human subjects. We believe it will be of value to add another report to the discussion whether it is possible or not.
Part I.
The devices for experiments are the same as that of Hudgins', except in just a few minor parts. In Experiment I, the conditioned stimulus was the sound of bell, while the unconditioned one was the light of 100 w. Both stimuli were presented simultaneously. The total number of reinforcement was about 100 over a period of 3 to 5 days. Subjects employed for this experiment were 6 adult men.
The procedure of Experiment II are very much like that of Baker and Wedell's. The conditioned stimulus, a weak tone of 1024 cycles near threshold was presented for 7 seconds through earphone. The unconditioned stimulus, light of 100 w., was presented for 4 seconds, 3 seconds after the conditioned stimulus had been given. During the 5 days of experiments, we gave the control experiment and 5 reinforcements on the first day, and from the second to the fifth day we gave 15 reinforcements every day. For this experiment 7 adults were employed.
In so far as our experiments are concerned, we could not get good results from Experiment I, though we reinforced 100 times or more in total. 3 cases among 6 could be considered to have been conditioned. In Experinent II, conditioned reflexes were established easily and surely. The results were far better than that of Experiment I. After 10 times of reinforcement we could observe the conditioned reflex with the latency of 3 seconds.
Thus we are able to conclude that, if the experimental procedure is good and adequate, it will be possible to condition human pupillary reflex.
Part II.
We further attempted to introduce a new method of conditioning pupillary reflex in human subjects. We have enough reason to believe that in conditioning any kind of human reflexes the differential reinforcement method is very efficient.
By use of this differential reinforcement method, we used a tone of 1000 cycles (20 db.) as the positive conditioned stimulus, and that of 468 cycles (20 db.) as the negative one. Duration of these stimuli were 7 seconds. The positive one was followed by the unconditioned stimulus of the light of 100 w., while the negative one was not.
In order to compare the results of the above mentioned method with the ordinary mothod of simple reinforcement using the tone of 1000 cycles (20 db.) as the conditioned stimulus and the light of 100 w. as the unconditioned stimulus, we examined 14 cases, 7 for the differential method and 7 for the ordinary method. After 40 times of differential reinforcements we could get conditioned reflex with the latent time of 4 seconds. On the other hand, it was not before 100 times of ordinary reinforcements that we could observe the conditioned reflex. Thus we may conclude that our newly introduced method is really effective and of value.
