“Color vision deficiency isn’t the end of the world. It’s just a different view of it.”

Karen Rae Levine

One of the most important functions of cognitive control is to continuously adapt cognitive processes to changing and often conflicting demands of the environment. Dopamine (DA) has been suggested to play a key role in the signaling and resolution of such response conflict. The direct assessment of DA function in humans is only possible by positron emission tomography (PET) so far, which is very expensive and highly invasive due to radioactive contamination and arterial blood sampling.

Blue–yellow color vision

What many people don’t know is that DA is found in high concentration in the retina. Accordingly, color vision discrimination has been suggested as an easy and “cheap” index of DA functioning. In particular, blue–yellow color vision impairment (CVI) has been used to indicate a low baseline level of DA. We measured color discrimination by means of the Lanthony D-15 Test. In this test 15 changeable color caps have to be ordered in sequence.

The task

For the first time at Leiden University, we used color discrimination to predict individual differences in the cognitive control by using the so called auditory Simon task. In this kind of task participants had to respond, for example, to the words "left" and "right" that were randomly presented to the left or right ear. Although the auditory location was completely irrelevant to the task, participants showed marked increases in reaction latency if the location of the stimulus was not the same as the required response (if, for example, they were to react left to a word that was presented in the right ear). This happens because of a “response conflict” between what we hear and what are we required to respond.

Presumption confirmed

As expected, participants showing better color discrimination were more efficient in resolving response conflict. Interestingly, participants showing a blue-yellow CVI were associated with less efficiency in handling response conflict. Our findings indicate that color vision discrimination might represent a promising predictor of cognitive control ability in healthy individuals.

Colzato, L.S., Sellaro, R., Hulka, L.M., Quednow, B.B., & Hommel, B. (2014). Cognitive control predicted by color vision, and vice versa. Neuropsychologia, 62, 55-59