Optimistic  and  pessimistic  decision-making  under  ambiguity:  causes  and  consequences  for  niche  choice  and  niche  conformance

Individuals differ in the way they perceive the world. From human psychological research it is known that these differences become particularly evident in ambiguous situations, in which individuals lack certain information about the matter under consideration. Symbolic for such situations is the often-quoted question: "Is the glass half-full or half-empty?" While some individuals would say the glass 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 a landmark study in 2004, this psychological theory has been transferred to animal welfare science. By utilizing judgement biases in ambiguous situations, a novel experimental technique has been introduced to distinguish between optimists and pessimists in animals.

However, since the tendencies to see the world either optimistically or pessimistically may have an immense impact on the kind of how individuals live and how they react to different situations, this framework does also apply to ecological contexts. Under natural conditions, animals are confronted with plenty of different decisions daily. For example, they have to choose among feeding habitats, select prey items, or allocate their foraging efforts in the face of conflicting demands. Since decision outcomes are crucially related to survival and fitness, genetically and environmentally induced biases in decision-making may influence how animals conform to a given environment, and what environments they prefer.

Based on these considerations the overall idea of this project is to transfer the study of decision-making under ambiguity from human psychology and animal welfare science for the first time to behavioural ecology. Using laboratory mice as model organism, the project will be designed as a proof-of-principle study, addressing two main research questions:

  1. How does one become an optimist/pessimist?
  2. What are the consequences of being an optimist/pessimist for niche conformance and niche choice?

Under the first objective, effects of genotype, environment, and gene-by-environment interactions on decision-making under ambiguity will be investigated. Since it is known from both human psychological research and animal welfare science that the way individuals interpret ambiguous information depends upon both environmental and genetic variation, we hypothesize that the interplay between genotype and environment leads to differences in decision-making under ambiguity. Under the second objective, effects of optimism and pessimism on an individual's preferences for specific environments (niche choice) as well as an individual's abilities to adapt to a particular ecological context (niche conformance) will be studied. We hypothesize that optimists choose other environments than pessimists and that they adjust differentially to a particular ecological context, thereby realising their own individualised niches.

Furthermore, epigenetic modifications of candidate genes in the central nervous system will be investigated. We assume that these candidate genes are up- or down-regulated due to a different extent of DNA methylation and that these gene expression and methylation patterns reflect the individual degree of optimism/pessimism. If the assumptions hold true, there is a great potential to transfer this idea further to other species and systems under more natural conditions, and to also include direct fitness measures in the study of optimism and pessimism. From a broader perspective, this will contribute substantially to a comprehensive understanding of niche choice and niche conformance concepts that gain increasing importance in the field of behavioural ecology.



Mus musculus

Life span: 1 - 2 years
Sexual maturity: 5 - 8 weeks
Metamorphosis: No
Offspring/ litter: 4 - 10
Social group: First same-sex groups, then solitary
Study phase: Adolescence to adulthood

Principle investigators

Prof. Dr. Helene Richter

Prof. Dr. Norbert Sachser

PhD students

Lena Bohn

Marko Bračić



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