DISCRIMINATIVE RESPONSES TO VISUAL STIMULI 469 



ES* and ES 5 are thrown to the left, the left side of the field, 

 partially illuminated by Li, will be darkened when PS, is opened^ 

 and that the subject will stop the chronoscope if he actuates 

 the reaction key SSi, and flash the signal lamp RL 4 and sound 



FIG. 2 



B, 50-ampere storage battery (120 volts) ; M , coils of field of chronoscope motor; 

 TF, 100 d.v. tuning fork; CCi, coil of stationary magnet of chronoscope; CC t , 

 coil of rotating magnet of chronoscope; PSi, PS 2 , PSt, switches actuated by 

 pendulum; ESi, ES t , ES S , ES<, ES 6 , switches operated by experimenter; SSi, 

 SSi, reaction-keys, pneumatic type, modified to form two-way switches, operated 

 by subject; L 3 , principal source of photometric field; LI, L 2 , auxiliary lamps, 

 whose extinction is the stimulus to reaction; Bz, buzzer actuated by subject in 

 event of incorrect reaction; RL\, RL t , RL 3 , RL 4 , lamps operated as resistances. 

 The lamps illuminating the interior of C are not shown. They were wired in 

 multiple with the rest of the system shown in figure 2, but were otherwise inde- 

 pendently controlled. 



the signal buzzer B if he actuates the right hand reaction switch 

 SS Z . If the bank of switches is thrown to the right, the functions 

 of Li and L 2 and of SSi and SS 2 are reversed. If ESi is closed, 

 the chronoscope is started by the breaking of PSi but the circuit 

 is not opened through either LI or L 2 . If the subject, from over- 



