1. Introduction;Appleby,1997
2. Novelty and curiosity as determinants of exploratory behavior;Berlyne;Br. J. Psychol.,1950
3. Curiosity and exploration;Berlyne;Science,1966
4. Long-term effects of a natural foraging task on aggression and stereotypies in socially housed pigtail macaques;Boccia;Lab. Primate Newslett.,1989
5. Broom, D.M., Johnson, K.G. 1993. Stress and animal welfare. Chapman and Hall, London, UK.