An Automatic Technique for Establishing Conditioned Reflexes

Abstract

A serious limitation of the usual conditioned-reflex techniques is the small number of animals which can be used by a single experimenter. To increase efficiency, a system has been developed in which the administering of stimuli and food and the recording of reactions are entirely automatic. Advantages of this procedure are: (a) that it offers the possibility of working simultaneously with several dogs (i.e. where two or more sound-shielded rooms are available); (b) that training which involves merely the repetition of stimuli will not necessitate the experimenter's concentrated attention but will leave him relatively free for other work; and (c) that, when the need arises, such training can be left to the supervision of a laboratory assistant.2 Motor-driven timer or circuit-closer. It is frequently desirable in conditionedreflex investigations to utilize rhythmical stimuli, e.g. a flashing light, an intermittent tactual prick, or a metronome beat. In Pavlov's laboratory the first of these stimuli is produced manually by closing a switch at the desired rate; and the intermittent tactual stimulus is administered by pressing a bulb. Pneumatically started metronomes provide rhythmical auditory stimuli, separate instruments being used for different rates. In the present arrangement, all intermittent stimuli are controlled by one device, a motor-driven timer. A brass disk driven by an electric phonograph motor is studded with small rivets arranged in concentric circles.3 A small rider can be set to trail over rivet-heads in any one of these circles. Each time the rider passes over a rivet-head it is lifted, thereby causing two flexible strips to touch. In a circle with 30 rivets, 30 contacts are made per revolution, and if a light is connected in the circuit it will flash 30 times. (See Fig. i, B.) 1National Research Fellow in the Biological Sciences. This technique has been worked out in the Conditioned Reflex Laboratory of the Henry Phipps Psychiatric Clinic, Johns Hopkins Medical School. The writer is greatly indebted to Dr. Adolf Meyer for extending the facilities necessary to carry on the project. He is also greatly indebted to Dr. W. Horsley Gantt for clarifying numerous questions regarding Pavlov's training procedures in the light of Dr. Gantt's intimate contact with the Russian work. Dr. Gantt, who established the Laboratory, has elsewhere described the sound-shielded room. The present paper should be read in conjunction with Dr. Gantt's more comprehensive description (forthcoming). 21n Pavlov's laboratory, work is carried on with the aid of a large number of medical students who train animals for credit toward a degree. Pavlov, or more accurately, one of his principal collaborators, takes these students in hand and sets them to work with one or two dogs on a specified problem. At the end of the training period, Pavlov comes and spends perhaps as much as a fortnight in personally verifying the results. 3A synchronous motor was not used because the city current was not at first telechronized.