n8 



THE QUARTERLY REVIEW OF BIOLOGY 



proper pigeon hole, to the greater happi- 

 ness and prosperity of the race. 



Unfortunately, there are serious objec- 

 tions to the whole test procedure. As yet, 

 we have no agreement on a definition of 

 what intelligence is. Which mental ac- 

 tivities involve it, and which do not? 

 For example, shall we include memory? 

 We find no general agreement. Some 

 testers include it, others exclude it. We 

 even find such authorities as Terman and 

 Thorndike including it at one time and 

 omitting it at others. Again, what about 

 imagination? Or language? Or the 

 power of attention? Or even motor abil- 

 ity? All these are included or omitted, 

 depending on the individual tester. Even 

 sensory perception has advocates on both 

 sides. There is, in short, no agreement 

 as to what constitutes intelligence, or in 

 what mental operations it is to be looked 

 for. 



We even find the plea advanced by Ter- 

 man that it is unreasonable to expect us 

 to define intelligence; that we can measure 

 it without knowing anything about its 

 ultimate nature, just as a physicist can 

 measure an electric current by means of 

 a galvanometer without knowing what 

 the ultimate nature of electricity is. But, 

 as Spearman points out, the physicist 

 knows where to look for his current; he 

 knows that he must read the galvanom- 

 eter which is in circuit with his current. 

 If he did not know which of his galva- 

 nometers was really in the circuit, and had 

 no means of finding out, he could deter- 

 mine very little about his current. In the 

 same way, if we do not know which tests 

 involve intelligence, we can hardly ex- 

 pect to measure it. 



Naturally, attempts have been made to 

 remedy this ambiguity. Definitions have 

 been proposed, but without great success. 

 Spencer's definition has often been used — 

 intelligence is that mental power which 



produces "conscious adaptation to new 

 situations." But we have here introduced 

 two more terms — "adaptation" and 

 "situation" — which, as Spearman shows, 

 are themselves interpreted according to 

 the fancy of the individual psychologist. 

 But even without this, the definition does 

 not tell us what kind of operation pro-J 

 duces adaptation, and we are as much at 

 sea as before. Other definitions, to which 

 the same objections apply, are the follow-, 

 ing: "The power of good responses from 

 the point of view of truth;" "the ability 

 to act effectively under given conditions;" 

 "that which can be judged by the degree 

 of incompleteness of the alternatives in. 

 the trial and error life of the individual;" 

 "a biological mechanism by which the 

 effects of a complexity of stimuli are 

 brought together and given a somewhat 

 unified effect in behaviour." One feels 

 that Professor Spearman is right when he i 

 advocates abandoning the term "intelli- 

 gence" as having lost any definiteness it 

 may once have possessed. 



But in addition to all this, and sup- 

 posing that we have denned our ' 'intelli- 

 gence" satisfactorily, still we have the task 

 of establishing the unity of function of 

 intelligence. But this is just what is 

 probably not true, if we are to accept the 

 results of the tests; for these tests are 

 reported to measure many different func- 

 tions, so that a high total score tells us 

 nothing about which functions are work- 

 ing well. And worse, each investigator 

 has his own set of functions into which 

 ' 'intelligence' ' may be analyzed. 



The forced abandonment of the unitary 

 "intelligence" leads naturally to the the- 

 ory that there are broad mental powers, 

 such as "judgment," "memory," "inven- 

 tion," "attention," each of which func- 

 tions as a unit. Here, again, we have a 

 doctrine which is widely held in the popu- 

 lar mind. In fact, in practice most of us 





