“…Thirdly, previous results suggest high stability in adult dogs of the investigated traits over shorter periods of time , as well as stability over longer periods of time with the exception of aggressiveness (Svartberg, 2005), indicating low influence by environmental factors. Fourthly, traits related to fearfulness and confidence have been found to be stable from young age in dogs (Royce, 1955;Pfaffenberger et al, 1976;Goddard and Beilharz, 1986;Slabbert and Odendaal, 1999), as well as in cats (Lowe and Bradshaw, 2001), in wolves (Fox, 1972) and in humans (Kagan et al, 1988). Thus, it is likely that the differences found in the investigated traits are not caused by environmental differences.…”