No two animals are the same. Individual differences in personality, memory or internal state may lead two different animals to make different choices or show different behavioural phenotypes. These inter-individual differences are key to understanding the life history strategies animals have adopted to adapt to their environments. However, despite the importance of inter-individual differences to our understanding of animal behaviour, there are still significant gaps in our knowledge of how inter-individual differences may affect group level behaviours. In this thesis I therefore aimed to determine how inter-individual differences in personality or memory may affect group level behaviour in social and subsocial invertebrates. In this thesis I describe lab-based behavioural trials on social and subsocial model systems (Temnothorax albipennis and Oniscus asellus respectively) to empirically test whether differences in inter-individual memories or personality affects group level decision-making and stability. I then further investigated the possible mechanisms behind our findings using agent-based modelling. The thesis shows that differences in both personality and memory played an important role in the emergence of group level behaviours and suggested that greater integration of the fields of animal personality and collective behaviour could greatly benefit our understanding of animal behaviour. I also explored the ethics and implications of carrying out animal behaviour studies. I suggested that research into invertebrate personality has many possible benefits both through tangible conservation interventions, as well as benefitting our theoretical understanding of animal interactions. However, I also highlighted the importance of continued re-evaluation of the ethics of the methods used in invertebrate research in light of shifting research into invertebrate cognition and public perception. I hope this work will spark further work into the role which inter-individual differences may play in group level behaviours as well as further interest in exploring the ethics and implications of this types of work
