Ivan Pavlov, answered from the texts and cited to the page.
Not all my dogs were alike, and the differences were not caprice. Some were bold, quick, and steady; some timid and easily undone; some sluggish; some volatile. I traced these differences to the fundamental properties of the nervous system — the strength of the excitatory and inhibitory processes, the balance between them, and their mobility, the speed with which one gives way to the other — and I found in the combinations of these properties the physiological ground of what the ancients, with a truer instinct than they knew, called the temperaments: the sanguine, the choleric, the phlegmatic, the melancholic.12
These types are largely inborn, the given constitution of the nervous system, and they decide, among other things, how much strain an animal can bear before it breaks. And break they do. When I set a dog a task that overstrains its nervous processes — forcing an ever-finer discrimination between a circle and an ellipse until the difference is past its power, or clashing excitation and inhibition in the same instant — the animal's whole behavior is deranged, lastingly: an experimental neurosis, produced to order and studied like any other physiological effect.3
From these breakdowns I read the physiology of nervous illness in man: the neuroses are the overstraining of a nervous system, and which system breaks, and how, depends on its inborn type.4
This is certainly an astonishing combination of the processes of excitation and inhibition. Thus all our dogs fall into four definite groups Two extreme groups of markedly excitatory and inhibitory animals, and two central groups of well balanced, equilibrated animals, but also different — one being quiet and the other exceedingly lively. We may consider this an exact statement Now can we apply this to man?Lectures on Conditioned Reflexes
In ith the more resistant nervous system it leads to a predo ce of excitation; in dogs with the less resistant nervous, to a predominance of inhibition.Conditioned Reflexes
He retains only excitatory processes, and all the inhibitory ones disappear almost completely. Such a condition we in our laboratory call neurasthenia, and it sometimes lasts for months. If in a dog standing at the opposite pole to this type, I apply the same procedure, conversely the excitatory processes are weakened, while the inhibitory prevail This state we think represents hysteria.Lectures on Conditioned Reflexes
Those that approximate to the first type@re ely and active, and in most cases aggressive; those that ah finito to the second type are quiet and restrained. I re er in particular one dog of the latter type whose re was in many respects extraordinary. I have never noticed it down on the floor while it waited for the experiment afte NEE tched from the kennel to the laboratory.Conditioned Reflexes
A major and influential part of Pavlov's system and the foundation of an experimental physiology of individual differences and of neurosis. The typology of nervous-system properties fed directly into the twentieth-century study of temperament — the Soviet differential-psychophysiology of Teplov and Nebylitsyn, and Hans Eysenck's biologically-based personality dimensions both build on Pavlovian nervous strength and balance — and the production of experimental neuroses founded the laboratory modeling of stress and breakdown that influenced behavior therapy and the physiology of psychiatric illness. It also raises, as sharply as any classic work, the ethical question of deliberately inducing lasting neurotic derangement in the experimental animals, a question the modern regulation of animal research answers very differently than Pavlov's laboratory did.