Persistent Problems in Systematic Psychology IV. Structural versus Functional Analysis

The purpose of this investigation was to determine the effect of iris color on critical flicker frequency (CFF). CFF thresholds were obtained on 56 male subjects between the ages of 18 and 25 divided into three groups on the basis of iris color (blue, green, and brown). The results indicate that iris color is a statistically significant factor in the determination of CFF (p < .05), though it was emphasized that the effect may have been due to the correlation between iris color and other ocular pigmentation. The blue-eyed group received the highest mean CFF and the brown-eyed group the lowest mean CFF with the mean CFF threshold of the green-eyed group falling between these values.