2021 Reprint of the 1925 Edition. Facsimile of the original edition and not reproduced with Optical Recognition Software. A class of educators, social workers, lawyers, and businesspeople at the New School for Social Research asked Mr. Overstreet to tell them "How human behavior can actually be changed, in the light of the new knowledge gained through psychology." He obliged, and the present book is his lectures, refined, amplified, and chastened by class discussion. Mr. Overstreet has achieved something of a triumph in the field of popularization. His book is readable and shrewd. This has become a classic of applied psychology and methods for influencing human behavior.