Pavlov's typology of higher nervous activity was the first systematic approach to the psychophysiology of individual differences.
Ivan Pavlov's ideas of nervous system typology came from work with his dogs and his realization of individual differences.
Pavlov started using observations and then used many experiments to show that there were many different distinguishing ways the nervous systems of dogs worked.
Pavlov introduced the ideas of strength of excitation and inhibition, as well as mobility, irradiation, and generalization in the central nervous system.
[3][4][5] Strength of excitation was considered to be the most important of the nervous system properties by Pavlov because we are often confronted by stimuli in the environment that grab our attention immediately.
[4] Pavlov looked at the balance between excitation and inhibition and determined that there were different types of nervous systems.
These second signals are, at their core, abstractions of reality and a method of generalization that is distinctive of human higher thought.
Pavlov's typology has been compared to psychologist Hans Eysenck's theory of the physiological bases of extraversion and introversion.
This is principally due to Eysenck's use of the Pavlovian concepts of excitation, inhibition, and equilibrium of cortical nervous processes.