103 A. Weiss et al. (eds.), Personality and Temperament in Nonhuman Primates, Developments in Primatology: Progress and Prospects, DOI 10.1007/978-1-4614-0176-6_5, © Springer Science+Business Media, LLC 2011 Abstract Objective behavioral tests can be useful tools in studies of the causes and consequences of individual differences in the temperament of nonhuman primates. This chapter begins by presenting guidelines for designing effective behavioral tests to produce valid and reliable measures of trait-like individual differences. It follows with a review of several well-characterized procedures for measuring individual differences in nonhuman primates on dimensions of neonatal temperament, anxiety, novelty seeking and impulsivity. Key points that emerge from this review include the value of establishing the test–retest reliability of traits, the importance of context for interpreting behavioral results, and the need for greater attention to specifying and validating the connection between the behavioral measures and the tempera- ment constructs of interest. Attention to these features will enhance our ability to identify genetic, physiological and environmental causes of individual differences in temperament, and the influence of temperament on outcomes of interest in biol- ogy, psychology and psychiatry. 5.1 Introduction Temperament is an important area of study for the psychologist interested in the social and developmental consequences of individual differences in response ten- dencies, and for the evolutionary biologist interested in ecological influences and fitness outcomes of behavior. There is evidence that temperament and its physiolog- ical underpinnings are related to immune functioning and disease susceptibility, and L.A. Fairbanks (*) Department of Psychiatry and Biobehavioral Sciences, Semel Institute, University of California, 760 Westwood Plaza, Los Angeles, CA 90095, USA e-mail: lfairbanks@mednet.ucla.edu Chapter 5 Objective Behavioral Tests of Temperament in Nonhuman Primates Lynn A. Fairbanks and Matthew J. Jorgensen