J. -PSYCHOLOGY. 189 



field. In this he has again been over-influenced by the great founders of 

 his science. Consider the work of Helmholtz and of Hering on visual 

 reactions. The former, with his very predominantly physical outlook, 

 laid the burden of explanation always upon what the stimulus and varia- 

 tions of the stimulus can do. Only when he got into tremendous difficulties, 

 as with simultaneous contrast, did he invoke processes, not directly visual, 

 seated in the observer himself ; and then, at once, his explanations 

 became confused and unconvincing. Hering, being far more dominantly 

 physiological, turned to a study of the immediately functioning mechanism. 

 He, however, seemed to set the stage for much so-called psychological 

 interpretation in later days, by elaborating a sort of speculative physiology 

 in his theory of anabolic process within a local sense organ. When a 

 psychologist takes up a problem of special sense reaction, his whole 

 training and outlook force him to lay due weight upon the wide variability 

 of such response when it takes place in its normal organic setting. If he 

 has his eye upon the physiological mechanisms this variability constantly 

 forces him back beyond the immediate peripheral functions to more 

 central processes. Then, as again and again in the history of the subject, 

 he is tempted to draw fanciful diagrams of the brain, laid out neatly into 

 all sorts of areas of function ; or, as is perhaps more common nowadays, 

 he relapses into wholly speculative physics and physiology of the central 

 nervous system. This is only trying wildly to do what the real physicist 

 and physiologist are most chary of attempting, except as a kind of game, 

 and it is no wonder that many of the more scientific psychologists are some- 

 what discouraged, while other people find it difiicult to take the psychologist 

 seriously. 



Yet it is not the psychologist's view of the problem, but his handling 

 of it, that has been faulty. Suppose we are investigating some specific 

 sensory threshold. The response of our observer will be determined by a 

 number of groups of factors. There are the physical characters of the 

 stimulus : its intensity defined physically, its duration, often its medium 

 of conduction to the sense organ concerned, relevant facts of its physical 

 and chemical structure. There is the absolute sensitivity of the local 

 responding physiological system, though this can never be absolutely 

 measured short of cutting it out of its organic setting, which is just what 

 the psychologist must not do, though the physiologist certainly may. 

 There is the order of presentation of the stimulus in its series, which 

 raises problems already touched upon in connexion with the psychophysical 

 methods ; and the correlated physiological questions of the state of adapta- 

 tion at the moment of the sensory system. Operating over and above and 

 through all of these are the tendencies, attitudes, moods, intellectual and 

 emotional habits of the observer, the states variously characterised as 

 states of confidence, hesitation, doubt, timidity, assertiveness, certainty. 

 An image, flashing out suddenly at a given point, may change the whole 

 character of a response and of succeeding responses. So may the verbalisa- 

 tion or formulation of a judgment. These so-called higher mental 

 processes are precisely the psychologist's main concern. They can be 

 experimentally set up and controlled to a large extent, while the other 

 factors are kept relatively constant. It is our business to show how they 

 are set up, and how they then powerfully determine reactions within the 



