E. GARCIA-AUSTT, J. BOGACZ AND A. VANZULLI 



615 



The interruption of the flicker by regular periods of darkness contri- 

 buted a new motive oi' interest to the flashes. Persons subjected to these 

 tests stated that owing to the monotonous repetition ot the continuous 

 flicker their attention decreased (habituation). In these circumstances when 



40 200 560 »0 680 840 lOOOnbflOJOIWHWO ( 5 5 7 9 ^1 15 <5 1 

 FLASHE:S(CF5) TBIAL5(DFS) 



(DFS 



5 ? 7 ; 



TRIALS 

 + TACTIL STIMULI) 



Fig. 6 

 Climiges of the visual evoked response hy effect of continuous and discontinuous flicl<er stinuilation and 

 through tactile-flash association. Ordinates, percentage of initial peak to peak amplitude of the 

 evoked response. Abscissas, times, represented by the number of flashes during the continuous 

 flicker stnnulation (CFS) at a frequency of 4/sec. and by trials carried out every 10 seconds witli 

 discontinuous flicker stimulation (DPS) at the same frequency for 10 seconds. Lead 02-right 

 mastoid. Stroboscope at a distance of 3 m. from the retina. Eyes open. In the first part of the 

 experiment with CFS an irregular reduction of the amplitude is observed. But if under these 

 conditions of habituation a DFS is employed the amplitude increases quickly. However, after 

 a few trials it tends to decrease again. If under these new conditions during the DFS every flash 

 is simultaneously associated with a brief tactile stimulus (tactile-flash association) the response 

 again increases in amplitude until the end of the e.xperiment. 



the flicker was suspended for the first time for a few seconds they beheved 

 the experiment to have terminated. However, after a few trials associating 

 darkness and flicker they realized that after a certain constant period of 

 darkness the flashes were always resumed and then their attention to the 

 flashes increased. In other words the interruption of the flicker gave new 



