We might refer to someone’s personality as “mousy,” but in truth, mice have a range of personalities nearly as great as our own. ...A quantitative understanding of the traits that make each animal an individual might help answer some of the open questions in science concerning the connections between genes and behavior. The findings of this research were published in Nature Neuroscience. Dr. Oren Forkosh, then a postdoctoral fellow who led the research in Prof. Chen’s group in Germany, explains that understanding how genetics contribute to behavior has remained an open question. Personality, scientists hypothesized, might be the “glue” that binds the two together: both genes and epigenetics (which determines how the genes are expressed) contribute to personality formation; in turn, one’s personality will determine, to a great extent, how one behaves in any given situation.

Personality is, by definition, something that is individual for each animal and something that remains fairly stable for an animal over its lifetime. Human subjects are generally given personality scores based on multiple-choice questionnaires, but for mice, the researchers needed to start with their behavior and work backward. The mice were color-coded for identification, placed in small groups in regular lab environments – with food, shelter, toys, etc. – and allowed to interact and explore freely. These mice were videoed over several days, and their behavior analyzed in depth. All together, the scientists identified 60 separate behaviors, including approaching others, chasing or fleeing, sharing food or keeping others away from food, exploring or hiding. ...