PhD ceremony Ms. G. Gracceva: Challenging the stability of personality. Studies on developmental plasticity in rodents

PhD ceremony: Ms. G. Gracceva

Dissertation: Challenging the stability of personality. Studies on developmental plasticity in rodents

Promotor(s): prof. T.G.G. Groothuis, prof. J.M. Koolhaas

Faculty: Mathematics and Natural Sciences

The thesis of Giulia Gracceva focuses on how personality develops in early life and to what extent it can be (perhaps adaptively) modified by the early life environment. Over the past decade it has become clear that also non-human animals have personalities. Consistent differences in behaviour between individuals of the same sex and species attract a lot of attention from behavioural ecologists and evolutionary biologists. However, because personality has been assumed to be relatively stable over a lifetime, developmental plasticity has hardly been studied.

Gracceva hypothesized that in wild-type rats, food, body mass, and hormonal conditions of the mother during pregnancy, as well as the number of brothers relative to sisters, may affect the personality of the offspring. Additionally, she examined whether in the common vole, experiencing different seasons in early life may affect personality, as voles are expected to adjust personality to differences in the social environment and food conditions between spring and summer. The three most important findings of Gracceva are 1) in the wild-type rat, important behavioural traits of personality such as aggression and anxiety are relatively insensitive to environmental manipulations, but non-specific early environmental factors such as handling, strongly affect the linkage between these behaviours; 2) in the voles, in contrast, an effect on the expression of separate behaviours, but not on their linkage was observed, further highlighting the importance of comparative studies; and 3) variation in personality is related to the regulation of the stress hormone corticosterone.