28 ROBERT M. YERKES 



Problem 4. Third from right end. 



1-6 (4); 5-8 (6); 3-12 (10); 1-3 (1); 7-11 (9); 

 2-10 (8); 1-7 (5); 3-5 (2); 2-9 (7;) 1-5 (3). 



Problem 5. Alternately left end and right end. 

 8-12 (8); 1-10 (10); 3-8 (3); 6-9 (9); 1-9 (1); 

 3-5 (5); 7-11 (7); 5-12 (12); 2-8 (2); 4-6 (6). 



Problem 6. Progressively from right to left end of apparatus — 



toward left bv ones. 

 10-12 (12); 6-12 (11); 3-10 "(10); 8-12 (9); 8-10 (8); 

 1-9 (7); 5-8 (6); 4-9 (5); 2-11 (4); 3-7 (3). 



Problem 7. One place to left of middle key. 

 6-12 (8); 3-5 (3); 8-12 (9); 1-9 (4); 2-12 (6); 

 10-12 (10); 5-11 (7); 1-5 (2); 3-9 (5); 1-3 (1). 



Problem 8. Alternately second from right and second from left. 

 6-12 (11); 2-5 (3); 1-8 (7) ; 5-9 (6); 1-5 (4); 

 4-12 (5); 5-10 (9); 9-11 (10); 2-9 (8); 1-5 (2). 



Problem 9. To the right of mid-point in even group; or first 



member of second-half of group. 



3-10 (7); 1-4 (3); 2-7 (5) 1-2 (2); 3-12 (11); 

 8-11 (10); 5-12 (9); 1-10 (6); 5-10 (8) 11-12 (12). 



Problem 10. Alternately to left of middle key and to right of it. 

 1-7 (3); 8-12 (11); 2-10 (5); 10-12 (12); 1-9 (4); 

 3-9 (7); 1-3 (1); 6-10 (9); 6-12 (8); 3-7 (6). 



The various forms of problem serviceable in' connection with 

 the different methods and the detailed procedure for each remain 

 to be worked out. The methods have been thoroughly tried 

 out and have already yielded such valuable results that further 

 development and application is obviously desirable. There is 

 no reason why the same apparatus should not henceforth serve 

 for studies of reactive tendencies and ideational behavior by 

 the method of quadruple choices, that of delayed reaction, that 

 of multiple choices, and that of conditioned reflexes. 



We experimenters shall . doubtless do well to use our devices 

 to the limit of their applicability, seeking no less assiduously 

 new ways of employing existing experimental equipment than 

 we seek to invent new mechanisms. 



