The role of serotonin in animal personality

Interindividual differences in animal behaviour that are relatively consistent over time and context are referred to as animal personality. Personality has been recognized throughout the entire animal kingdom, in an array of species like molluscs, arthropods, fish, birds and mammals. The personality of non-human animals has been suggested to vary along five different axes, or continua; boldness-shyness, avoidanceexploration, activity, sociability and aggressiveness. Having a relatively fixed personality may seem nonadaptive compared to infinite behavioural plasticity so the individual would be able to respond adaptively to any changes in the environment. There can be physiological limitations to the phenotypic expressions of any trait, including behaviour. Variation in neuroendocrinology may thus explain why animals have personality. A candidate neurochemical that potentially proximately influences and forms personality, is serotonin (5- HT), one of the most omnipotent neurotransmitter of the animal body. In the many realms of the serotonergic system, there may arise individual differences which forms a proximate basis for differences in personality. In this review paper, I discuss the impact of the serotonergic system on a few different personality traits. Depending on the individual’s motivational state, serotonin can dampen or enhance aggression. Serotonin correlates negatively to anxious traits. Feeding behaviour is affected by serotonin in seemingly opposing directions. Overall, serotonin seem to underlie many behaviours that describe animal personality