Abstract
Personality and its various sub-traits such as temperament can be defined as behavioural attitudes that remain relatively stable across time and situations. However, various personality models exist. Contrasting their strengths and weaknesses leads to the conclusion that there is presently no model that is truly superior to others in depicting animal personality. Furthermore, the present review highlights aspects in which animal, and in particular equine personality potentially relate to animal welfare. Three approaches are examined which may be taken to improve welfare: (1) genetically selecting for personality traits that make the horses better adapted to their designated work and/or husbandry conditions, (2) assessing personality in individual horses to optimize matching with owners and type of work and (3) influencing the ontogeny of personality traits, e.g. by specific training and husbandry regimes. Each of these strategies has its merit, but as a prerequisite, valid personality assessment methods are required. Although publication bias is likely present, most testing procedures yield acceptable inter-observer reliabilities and repeatabilities across time, even if repeatability across situations tends to be comparably low. Heritability estimates ranging mostly between h2=0.15 and h2=0.40 for traits assessed in personality tests are likewise promising. Research has paid less attention to intra-observer reliability, construct validity or discriminant ability, but based on pleiotropy it is argued that the latter is not essential for a trait to be valid. Therefore, some valid methods are available for use in assessment and subsequent selection of horses or personality-influencing strategies, ultimate resulting in reduction of stress in horses' everyday life.