THINKING- An Introduction to its Experimental Psychology by GEORGE HUMPHREY. PREFACE: THIS BOOK WAS begun in 1934 at the suggestion of Professor F. C. Bartlett. 1 The first draft was practically finished when war broke out, and for various reasons the book had to be laid aside for nearly ten years. The whole manuscript has now been revised and a good deal of it rewritten. Those who have read the manuscript in duplicated form at various stages have made many suggestions about its content. Some, for instance, have urged that the section on the Wiirzburgers, which now occupies three chapters, should be deleted or at least shortened. Others have been equally urgent that these chapters should be left intact. With the exception of some pruning where the argument seemed to have become diffuse, the Wiirzburg chapters have been left substantially as they were originally written, and for the following reasons. The contribution of this group still stands in its own right as the most massive, sustained, and acute experimental attack on the problem of thought. It is true that the vocabulary, and behind it the general theory, employed by these men is now out of date, and that for this reason their work often seems arid and devoid of significance for modern psychology. But actually they were concerned with a set of general problems that are still very much alive to-day. Of these, the most important can thus be stated Can organic response be reduced without remainder to response strictly correlated with individual receptors The problem has a long history and is still being debated. At the present time, for example, Hull and his pupils are maintaining a theory of behaviour built on the foundations laid by Pavlov, and which maintains that behaviour can be explained in terms of funda mentally unchanged motor response to specific receptoral stimulation. 2 The controversy concerning imageless thought debated the same problem, couched, however, in terms of experience. The Wiirzburgers were concerned with the question whether Experience can be built up out of experiences referable to particular sense modalities. The problem is the same, though the co-ordinates have been changed. In the same way, the Wiirzburg workers found it 1 Now Sir Frederic Bartlett. 2 The controversy over the continuity theory of learning sprang of course from the original theory. For a simple statement, both of Meaning as treated in terms of the referential function and of much of the material collected in this book, see G. Humphrey, 1948, Directed Thinking Dodd Mead. necessary to postulate the Determining Tendencies and the Task to supplement their version of Associationism, which is fundamentally a peripheral hypothesis. The modern counterpart is the Motive, which has been extensively investigated during the past twenty years, and which sprang out of exactly the same difficulty as theirs. Thus, in addition to its intrinsic merit, the work of the Wurzburgers gives a kind of preview of work which is central for modern experi mental thinking. No apology should be necessary for treating it in some detail. It may be added that the original sources of both the Wurzburgers work and that of their successor, Selz, are becoming increasingly difficult to obtain. Another point of criticism has been the treatment of meaning which, in the original writing, was described by the use of the term referential function. This appeared to be at least a neutral term, stating the facts if it did not illuminate them. However, it now seems fairly clear that many of the difficulties that have surrounded the concept of meaning grew up at a time when psychologists had almost forgotten that a human being is a biological system living in a bio logical environment...