the antecedents of Pavlov’s brain model may be traced directly to the concepts of Sechenov and Jackson, who were both pioneers in the field of neurophysiology. Sechenov and Jackson, in their turn, were influenced by the philosophical concepts of Locke and Spencer, respectively. Locke promulgated the theory that psychological development of the mind depends entirely on the activity of the sense organs, a theory expressed in his famous doctrine that the mind of a newborn child is a tabula rasa, which is written on by experience alone. Sechenov, with his reflex theory, elaborated on Locke in his monograph Reflexes of the Brain (1863). According to Sechenov, all acts of life, both physical and psychological, are basically reflex, and any voluntary, involuntary, or psychological action in the reflex arc begins with a sensory stimulus-impulse related excitation and continues by means of a definite psychophysical act ending in muscular activity. In this view, not only psychological development, but all activity, depends entirely on the activity of the sense organs.