The puff test. An attempt to assess the intelligence of young children by use of a conditioned reflex.

Krasnogorski (1913), who was working with Pavlov in St. Petersburg, described his experiments on establishing conditioned reflexes in children. His methods were expanded by Mateer (1918) whose paper will be described later. No further relevant work on the subject was published until Pavlov's famous book on Conditioned Reflexes (Pavlov, 1927). This work is well known and only a brief summary of it will be given here. Pavlov distinguished between inborn and conditioned reflexes. If food is placed in a dog's mouth, the dog salivates. That is an inborn reflex. If the dog salivates when he hears the footsteps of his master coming to feed him, that is a conditioned reflex. A conditioned reflex must be founded on an inborn reflex or a new stimulus can be used for a well-established conditioned reflex. There are three components of a conditioned reflex: the unconditioned stimulus, which gives rise to the unconditioned reflex, and the conditioned stimulus which, after being paired with the uncon-ditioned stimulus, elicits the same response. In the example given above the unconditioned stimulus is the food, the reflex the salivation and the conditioned stimulus the footsteps. When conditioning is established the reflex will appear if the conditioned stimulus alone is exhibited. Pavlov stressed that successful conditioning could only be expected under optimal circumstances. Irrelevant stimuli such as fear, noise or the desire to micturate tend to prevent the establishment of conditioned reflexes in animals. If a conditioned reflex is not periodically reinforced by the reintroduction of the unconditioned stimulus it gradually becomes extinct. This fading away of the reflex is known as deconditioning. Even after deconditioning, however, the reflex may spontaneously regenerate with the passage of time. Pavlov's book referred only to experiments on animals, but other workers tried similar experiments on children. One of the earliest attempts to utilize the concept of the conditioned reflex in diagnosis was reported by Aldrich (1928). He conditioned pain, in the form of a pin-scratch on the sole of the foot, and the sound of a dinner gong, in order to demonstrate hearing in a 3-month-old infant. It was found that the younger the child, the harder he was to condition. Wenger (1943) described some controlled experiments in which he tried to condition infants to blink in response to an electric shock which had been coupled with a bright light shining into their eyes. Later some of the infants blinked with the …