The aim of the present study was to broach the question of the relative influence of different genetic and
environmental factors on different temperament/personality traits of horses (Equus caballus). The
researchers submitted 702 horses to standardized experimental tests and investigated 9 factors, either
genetic or environmental. Genetic factors, such as sire or breed, seemed to influence more neophobic
reactions, whereas environmental factors, such as the type of work, seemed to play a more dominant role
in reactions to social separation or learning abilities. Additive effects were evident, showing how
environmental factors may modulate behavioral traits. This study constitutes a first step toward understanding
the relative weights of genetic factors and how the environment may intervene in determining
individual behavioral characteristics.