Very practical reasons account for the introduction of motivation research in-the field of market study. When it becomes desirable to influence consumer behaviour and attitudes, a simple assessment is no longer adequate and there is an obvious need for a deeper knowledge of their roots. The word motivation expresses this concept of psychological causality. But the very concept of causality is by no means a simple one, as many Western thinkers have repeatedly observed. Aristotle felt that it was necessary to distinguish between four kinds of causes. In modern times, Malebranche and Hume have demonstrated that in the realm of psychology as well as in physics , we are utterly unable to comprehend the effectiveness of a given cause, and that, however vivid, our spontaneous intuitions of causality are hollow and meaningless.