Lateralisation in humans and other vertebrates involves the input of sensory information more strongly to the brain hemisphere responsible for a required task. Examples include eye preference, and asymmetric inputs of sound and smell , which improve cognitive tasks when individuals process stimuli. Interestingly, the degree and direction of lateralisation can also vary between individuals depending on personality phenotype, which affects their behavioural responses towards stimuli. However, it is not known how sensory information is lateralised when processing stimuli and simultaneously organising a behavioural response towards them. In a recent study we show that this can be accomplished by separate senses being lateralised differently. We demonstrate for the first time that electrosensing is lateralised in weakly-electric fish, Gnathonemus petersii, and find that the direction of laterality towards an unfamiliar object varies with personality; bold fish lateralise towards the right and timid fish the left hemisphere. By contrast, visual inputs do not vary between individuals, but are lateralised across the population towards the left hemisphere, responsible in fish for the analysis of unfamiliar objects. This species has a stronger representation of electrical than visual signals in its brain , which could drive the differences between senses in functional laterality. This novel observation reveals that different senses can be selected for lateralisation in different ways, depending on their dominance, which has implications for the evolution and development of brain structure.
We are often determined by our personality, a set of traits that develop during our lifetime and make us who we are. Our personalities can determine our actions and our emotions. Can they, however, determine how we process information? The way we assess our surroundings is intricately linked to how we feel and act. A typical pattern is that an unusual situation might impose fearfulness and stress, which can lead to the negative assessment of that situation and our active avoidance of it. However, an individual with a bolder personality is less likely to avoid and more likely to approach a novel situation, which could indicate a less pessimistic assessment. Recently, personality-based cognitive biases have been tested in animals, but mostly from the perspective of speed-accuracy trade-offs. These trade-offs propose that animals with bolder personalities are likely to make haste decisions; decisions which are faster but less accurate. The evidence is convincing, but attempts to apply it to other processes of cognition, e.g. learning and memorisation, have been less successful. For example, bold guppies are faster at learning from others, but are not less accurate. This is because cognitive processing is complex, consisting of several interacting functions. Therefore effects may be limited to particular functions or affect some functions indirectly through others. Further, personality determines particular tendencies which can be intricately related to how individuals prioritise risk and reward, but also how they collect information and make associations. For one, personality may influence information-collection, via levels of active exploration. In addition, more reward motivated personalities may be able to associate a reward to an act or a stimulus, e.g. food to locations, faster. In this new study on elephantnose fish, we show just that. Bolder fish, which exhibited higher levels of exploration and shorter approach tendencies, also decided faster and were more accurate during training at reaching a food-rewarded location. As an indirect effect of their greater accuracy they also learned faster, which shows that indeed the explorative, reward-driven behaviour of bold fish predicts their cognitive performance in a spatial context. Therefore, by affecting our assessment and our behavioural response to risk and reward, personality also affects our ability to make associations and learn.