Once an optimist, always an optimist? Studying cognitive judgment bias in mice

This repository contains raw data and analysis code for the manuscript
entitled "Once an Optimist, Always an Optimist? Studying Cognitive
Judgment Bias in Mice" from Marko Bračić, Lena Bohn, Viktoria
Siewert, Vanessa von Kortzfleisch, Holger Schielzeth, Sylvia Kaiser,
Norbert Sachser, S. Helene Richter, accepted for publication in the
journal Behavioral Ecology. The aim of the study was to investigate the
causes and stability of cognitive judgment bias (aka
"optimism"). Individuals differ in the way they judge ambiguous
information: some individuals interpret ambiguous information in a more
optimistic, and others in a more pessimistic way. Over the past two
decades, such “optimistic” and “pessimistic” cognitive judgement biases
(CJBs) have been utilized in animal welfare science as indicators of
animals’ emotional states. However, empirical studies on their ecological
and evolutionary relevance are still lacking. We, therefore, aimed at
transferring the concept of “optimism” and “pessimism” to behavioral
ecology and investigated the role of genetic and environmental factors in
modulating CJB in mice, using an automated, touchscreen-based active
choice paradigm. In addition, we assessed the temporal stability of
individual differences in CJB. We show that the chosen genotypes (C57BL/6J
and B6D2F1N) and environments (“scarce” and “complex”) did not have a
statistically significant influence on the responses in the CJB test. By
contrast, they influenced anxiety-like behavior (assessed in the elevated
plus maze (EPM), an open field test (OFT), and a free exploration test
(FET)) with C57BL/6J mice and mice from the “complex” environment
displaying less anxiety-like behavior than B6D2F1N mice and mice from the
“scarce” environment. As the selected genotypes and environments did not
explain the existing differences in CJB, future studies might investigate
the impact of other genotypes and environmental conditions on CJB, and
additionally, elucidate the role of other potential causes like endocrine
profiles and epigenetic modifications. Furthermore, we show that
individual differences in CJB were repeatable over a period of seven
weeks, suggesting that CJB represents a temporally stable trait in
laboratory mice. Therefore, we encourage the further study of CJB within
an animal personality framework.