SFB-Trr 212

The behavioural ecology of optimism and pessimism: Do optimists and pessimists realise different individualised niches?

Individuals differ in the way they judge about ambiguous information. Symbolic for such situations is the often-quoted question: Is the glass half-full or half-empty? While some individuals would say it is half-full, others would describe it as half-empty, indicating the existence of optimistic and pessimistic decision-makers (i.e., “optimists” and “pessimists”). In 2004, this psychological framework has been transferred to animal welfare science, allowing to also distinguish between optimists and pessimists in non-human animals. Since under natural conditions, animals are confronted with plenty of decisions daily (e.g., choose among feeding habitats or select prey items), the tendencies to see the world either optimistically or pessimistically, however, may also have an immense impact on survival and fitness. In the first funding period, we therefore aimed at transferring the concept of optimism and pessimism from animal welfare science to behavioural ecology. Using laboratory mice as a model species, we could show that optimism and pessimism represent relatively stable traits that cannot be solely explained by genotype, environment, or by genotype-by-environment interactions. Furthermore, we could demonstrate that there is no overlap between systems of optimism/pessimism and fear/anxiety. In the second funding period, we now aim at expanding this idea further and investigate whether optimists and pessimists realize different individualized niches. In particular, we will pursue the following research questions:

1. Do optimism and pessimism levels change over a lifetime?
2. Are optimism and pessimism levels linked to other individual characteristics (e.g., risk-taking, exploration)?
3. What are the consequences of optimism and pessimism for niche choice and niche conformance?

As testing mice in a touchscreen-based optimism/pessimism test turned out to be extremely time-consuming, we will switch the model species and work with laboratory rats to guarantee a fast characterization of optimists and pessimists. From a broader perspective, this will allow to concentrate more effectively on ecological consequences of optimism and pessimism, thereby contributing to a deep understanding of how individual traits shape niche choice and conformance processes.