J.— PSYCHOLOGY 219 



Table II. 



Ishihara Test. 



Frequency in percentages of normal and colour-blind responses for N, N — , 



and colour-blind groups. 



The frequency of responses other than normal and colour blind has 

 been omitted. 



N = 286 males : N— = 48 males : C. B. = 45 males. 



Table II shows the results from the Ishihara test when given to these 

 three groups. The percentage frequency of the responses in each group 

 has been calculated with regard to normal responses and colour-blind 

 responses. The table is read thus : in plate V, 56 per cent, of group N 

 read the figures correctly as the normal do, that is, read them as 74, whereas 

 1 1 per cent, of group N read the figures as the colour blinds do, that is, 

 read them as 21. The frequency of responses other than normal and 

 colour-blind has been omitted. In the N— group, 29 per cent, gave the 

 normal response, 31 per cent, the colour-blind response. In the colour- 

 blind group, o per cent, gave the normal response, 81 per cent, gave the 

 colour-blind response. 



Plates II and III are never wrongly read by either the N or N — group, 

 but Plate III seems the better diagnostic test of colour blindness, as 71 

 per cent, of the colour blinds failed on it, and only 21 per cent, passed. 

 Plate IV is equally good, although • 5 per cent, of the N group and 4 per 

 cent, of the N— group gave the typical colour-blind responses. Plate V 

 which is read as 74 by the normal and as 21 by the colour blind is said by 



