Ivan Pavlov, answered from the texts and cited to the page.
When a tone of 1000 vibrations per second is made a conditioned stimulus for the food reaction, other tones spontaneously acquire similar properties — and the effect diminishes proportionally to the interval between those tones and the original.1 The same holds for the skin: establish a conditioned reflex from mechanical stimulation of one point, and stimulation of neighboring points will elicit the same reaction, the effect weakening with distance from the original site.2
This is what I call generalization of stimuli, and it is not a curiosity or an error of the nervous system — it is a biological necessity. The interpretation is straightforward. Natural stimuli are never rigidly constant; they range around a particular quality and strength in a common group.3 The hostile sound of a beast of prey serves as a conditioned signal to a defence reflex regardless of variations in pitch, strength, or timbre — the animal that waited for an exact repetition of the signal would be dead before it acted.
Generalization is the nervous system's recognition of this fact, and its physiological basis is equally clear: excitation arriving at a point of the cerebral hemispheres spreads and irradiates over the corresponding region of the brain, so that all stimuli of a given category become connected with a definite activity of the organism.4 Generalization, however, is only the first movement.
It is always followed — when the organism's life demands it — by differentiation, which is the work of inhibition. By reinforcing the original conditioned stimulus repeatedly while leaving allied stimuli without reinforcement, those allied stimuli become negative, inhibited, inactive.5 The inhibitory process develops at the corresponding cortical point and, precisely as excitation irradiates, so too does inhibition spread from its original point to neighboring regions.6
Differentiation is the analytical achievement built upon this inhibitory foundation — the most delicate relation of the organism to the elements of its external and internal worlds.7 So the sequence is: first a broad, approximate, biologically useful connection with the environment as a whole; then, where precision is demanded, its replacement by an exact and specialized connection with a definite stimulatory unit.8
Generalization is synthesis; differentiation is analysis. Both are expressions of the same cortical dynamics — irradiation and concentration of the nervous processes — and neither can be understood without the other.
if a tone of 1000 d.v. is established as a conditioned stimulus, many other tones spontaneously acquire similar properties, such properties diminishing proportionally to the intervals of these tones from the one of 1000 d.v.Conditioned Reflexes
if a tactile stimulation of a definite circumscribed area of skin is made into a conditioned stimulus, tactile stimulation of other skin areas will also elicit some conditioned reaction, the effect diminishing with increasing distance of these areas from the one for which the conditioned reflex was originally established.Conditioned Reflexes
natural stimuli are in most cases not rigidly constant but range around a particular strength and quality of stimulus in a common group.Conditioned Reflexes
We must suppose that in all these cases the excitation arriving at a certain point of the cerebral hemispheres spreads and irradiates over the corresponding part of the brain. It is only in this way that all the stimuli of the given category could become connected with a definite activity of the organism.Lectures on Conditioned Reflexes
By repeating the stimulation of our chosen point in the skin and accompanying it with feeding, and not accompanying the stimulation of the other points by feeding, these latter become inactive, now they are differentiated, negative, conditioned stimuli.Lectures on Conditioned Reflexes
If you now apply the fifth (negative conditioned stimulus) apparatus, then for some time afterwards all the upper (positive conditioned stimulus) apparatuses are without effect. The inhibitory process has irradiated from its original point to neighbouring regions of the cerebral hemispheres.Lectures on Conditioned Reflexes
This form of inhibition gives us the ability to analyse, which is the most delicate relation of the organism to the elements of the external and internal worlds.Lectures on Conditioned Reflexes
the approximate, general, and under some conditions useful connection with the environment as a whole is replaced by a precise and definitely specialized connection with a definite stimulatory unit.Conditioned Reflexes