The Ishihara Color Test is a color perception test administered for the purpose of diagnosing red-green color deficiencies in patients. Essentially, it consists of a set of colored plates, each of which contains a circle of variously colored dots – the dots differ in size and color. Somewhere within the dots is some form of a figure – typically a number; this is usually visible to those with normal color vision and difficult or impossible to see for those with red-green defects. The reverse is true with some other plates. In addition, there are four different kinds of plates: those on which individuals with a defect will see different things than will individuals with normal vision (transformation), those that may only be recognized by normal color vision individuals (vanishing), those that only individuals with defects can view (hidden digit), and those intended to distinguish between protanopia and deuteranopia (diagnostic).
If one “incorrectly” recognizes a certain number of the first fifteen plates (four, by Australian standards), then one is termed to have a color vision defect. However, I’ve begun thinking that this could be problematic for young children, who in some cases may be slightly hazy where numbers are concerned. Others have considered this, too – according to studies conducted in Sydney in 2005, it appears that about 75.8% of children with normal color vision make significant errors on some plates. This could be a fundamental flaw of the test.
How could the Ishihara Color Test be modified to reduce the risk of numerical confusion errors? It seems quite possible to me that young children might, say, mistake a “1” for a “7” if both numbers are given with serifs. Perhaps a sans serif “1” would be of help, but then, the effectiveness of plates like Ishihara 9 is based on “4” becoming “1”; this can only be accomplished with serifs. Perhaps including a component of the test that involves reproducing the figure on paper instead of identifying it verbally could circumvent the problems caused by younger children’s poorer communication skills.