Do not in any way 'prove the rule,' but on the contrary are completely valid disproofs, even though they are rare, indeed, so long as one single exce… - Kurt Zadek Lewin

In its present state of development psychology must be thought of as a young science. There is only one field in which it is relatively well established and in which it has advanced steadily: this is the psychology of sensation and perception. The scientific character of this field is fully recognized. Its findings are based almost entirely on experimental evidence, and even when its theories are in conflict one feels that as far as method is concerned it stands on relatively firm ground. The situation is different with the psychology of will, of needs, and of personality despite the fact that these fields have always attracted popular interest. As recently as fifteen years ago it was assumed that they, by their very nature, were not amenable to scientific methods. The little experimental work that had been done seemed too artificial and abstract to give an insight into the real processes. It was generally accepted that experimental investigations of these elusive and highly complicated processes were intrinsically impossible, at least in so far as human beings are concerned. Thus in Europe these problems were treated in a half-literary, half-philosophical way, and in America the tendency was to study individual differences by means of tests.

The choice between two pleasant things is generally easier than that between two unpleasant unless questions are involved which cut deeply into the life of the individual. Such a conflict situation can upon occasion also lead to an oscillation between two attractions. It is of considerable importance that in these cases a decision between two attractions. It is of considerable importance that in these cases a decision or one goal alters its valence in such a way as to make it weaker than that of the renounced goal.

Only a few years ago one could observe, at least among German psychologists, a quite pessimistic mood. After the initial successes of experimental psychology in its early stages, it seemed to become clearer and clearer that it would remain impossible for experimental method to press on beyond the psychology of perception and memory to such vital problems as those with which psychoanalysis was concerned. Weighty 'philosophical' and 'methodological' considerations seemed to make such an undertaking a priori impossible.