METHODS OF STUDYING VISION IN ANIMALS 3 



recommended for the study of " light vision.'" To Professor 

 Watson chiefly belongs the credit for the method and apparatus 

 herein described and recommended for the study of " color 

 vision.'" 



We have attempted, in this report, first, to indicate pointedly 

 the principal merits and defects of several of the more important 

 and commonly employed methods of studying vision, and, 

 second, to perfect and recommend, for all intensive quantitative 

 investigations, a procedure for testing light, size, form, and 

 distance perception, and a procedure for testing the various 

 aspects of color perception. It is our hope that this monograph 

 may prove of service to other investigators by enabling them 

 to avoid the use of eminently unsatisfactory, although commonly 

 used, methods, and by facilitating the adaptation to their 

 special needs of what we judge to be the more promising types 

 of procedure. 



At the outset, it is essential that we emphasize the ground 

 upon which we recommend certain procedures for standard- 

 ization. We have neither discovered nor devised perfect methods ; 

 we have merely done our best to propose methods whose scien- 

 tific value is obvious and whose possibilities of improvement 

 seem almost unlimited. Our standard procedures are recom- 

 mended only for thoroughgoing, intensive, quantitative work. 

 Simpler and more conveniently manipulated apparatus may 

 be used in the case of preliminary exploratory work. We do 

 not wish to discourage the use of crude and relatively uncon- 

 trollable methods for the study of vision, but we do most em- 

 phatically recommend that these methods be abandoned as 

 soon as the rough problem-defining portion of an investigation 

 has been completed. The employment of colored papers, 

 colored yarns, painted backgrounds, and similar conditions, 

 for the testing of color vision may yield valuable qualitative 

 results, and they may be used to advantage if the experimenter 

 realizes and clearly states that his control of the visual con- 

 ditions of his tests is extremely imperfect. In this methodological 

 investigation, it has been our aim to perfect procedures which 

 shall vastly increase the experimental control and describability 

 of the visual stimuli to which an organism is subjected. 



Without further introduction, we shall present our results 

 in accordance with the plan given in the table of contents. 



