Color Discrimination Provides Insight into the Relationship between Personality Cognition and Brain Morphology in the Western Mosquitofish (<b><i>Gambusia affinis</i></b>)

Recent studies on the differences in cognitive ability between individuals focused on two aspects: one is whether the individual differences in cognitive ability are related to brain size, the other is whether they pertain to certain personality traits. To explore these two hypotheses, we tested the personality traits, cognitive abilities, and brain volumes of western mosquitofish (<i>Gambusia affinis</i>). First, a color preference test was conducted to select two unbiased colors for <i>G. affinis</i> for subsequent cognitive tests. The results showed that <i>G. affinis</i> had a great preference for red and green to yellow and blue; therefore, the red-green combination was selected for the study of cognitive abilities. Then, we explored the relationship among cognition, personality, and brain morphology through cognitive abilities tests, personality traits, and brain volume measurements. We found that there was a trade-off among cognition, personality, and brain morphology. For example, more active individuals found food faster, but had also poor memory; Those individuals with larger corpus cerebelli were bolder while they were less likely to find food; The individuals that found food faster were more active and had a smaller inferior lobe. The color preference test provides a reliable way for selecting unbiased colors for behavioral studies in <i>G. affinis</i>. Meanwhile, our study indicates that there exists a balance mechanism among cognition, personality, and brain morphology.