The missing link: Exploring laterality and personality development in two fishes

This PhD thesis primarily investigated factors that may influence behavioural laterality and personality traits. I also examined the potential link between behavioural laterality and personality traits. Overall, I demonstrate how environmental factors, such as light and predation, can impact the development of laterality and personality using fish as animal models. Parents can also influence laterality of their offspring through genes and epigenetic effects. Additionally, I discovered a relationship between cognitive bias, laterality, and personality traits. I then explore how laterality may serve as a valuable indicator of welfare status and how environmental conditions can potentially influence laterality and associated behaviours. However, it's important to note that in none of my experiments did I find strong support for our hypothesis that behavioural laterality and personality traits are strongly correlated.
The findings of the second chapter suggest that early light exposure can influence laterality in Western rainbowfish but is lost by maturity. The third chapter reveals that parental exposure to predators results in offspring with bolder personalities, greater lateralization, and smaller body size in three-spined sticklebacks. The fourth chapter suggests that laterality in three-spined sticklebacks is influenced by maternal effects; offspring with marine mothers exhibit population-level biases in laterality. In the fifth chapter, I found that bold, lateralized fish tend to display more optimistic cognitive biases, shedding light on the connection between internal states and behaviour, particularly in a welfare context. The sixth chapter is a review paper discussing the importance of understanding laterality in the context of fish welfare across various human-fish interaction contexts.