There are three fundarnental properties of the nervous systern，the cornbination of which constitutes the type of nervous systern: the strength，balance (equilibliurn)，and mobility of the nervous
processes of excitation and inhibition.
Apperently，Pavlov consisted the strength of the nervous systern to be the most important property of the nervous systern. He suggested that the significance of the strength of nervous processes，
particularly the excitatory process，follows clearly from the fact that the environment often conveys unusual，extraordinaly events-stimuli of great intensity. Pavlov strongly related nervous system typology to the individual's ability to adapt to the environment，giving highest credit to the two strong，well-balanced types，and the lowest to the weak type. The most significant contribution to Pavlov's typology adapted to humans，especially to adults，has been made by the Moscow group working since the middle 1950s under Teplov and Nebylitsyn. The diagnosis of nervous systern properties should deal not only with CR procedures but with other psychophysiological measures as well，including sensory reactions and bioelectrical activity. These psychophysiological indicators have becorne the most important ones in the research of the Moscow group due to the fact that EEG indices enable the partiality phenornenon to be avoided. From the early 1970s，the theorising and empirical work of the Warsaw group，under the direction of Strelau，has made considerable impact on typological theory. In 1969 Strelau established a
Laboratory of Individual Differences at the University of Warsaw. Strelau defines temperament as a set of traits manifested in energy level，and in the temporal parameters of reaction. His main temperament dimension，reactivity，describes the relationship between stirnulus intensity and response amplitude，a relationship predictable from the Law of Strength. In this sense，his concept
is sirnilar to the Pavlovian notion of nervous systern strength-weakness.