Motivation is the hidden urge within us which impels us to behave in certain ways. This urge may be purely instinctive, like the need for food, it may arise from a rational decision to achieve a certain end or it may be the result of a combination of both these factors. Motivation is difficult to study directly, and its nature has to be inferred from a range of indirect sources. It develops in childhood, and from then on it is a vital part of our everyday experience. First published in 1969, Professor Vernon's book is an exposition of the fundamental psychology of human motivation, as opposed to motivational processes in animals, with which most books at the time of publication dealt. The principal effects of motivational frustration and conflict are also discussed. Experimental evidence is introduced whenever possible. The author has here drawn on her considerable experience as a lecturer and teacher to provide students with a sound basic knowledge of this important topic in psychology.