ABSTRACT
Individual differences in autonomic regulatory functions and their relationships to cognition, emotions, and behavior have long interested researchers in psychophysiology. Heart rate (HR) and HR variability have received considerable attention for their utility as noninvasive indices of autonomic nervous system (ANS) regulatory activity (Boomsma & Plomin, 1986; Fox & Porges, 1985; Hare, 1982; Izard et al., 1991; Kagan, Reznick, & Snidman, 1988; Matthews, Woodall, & Stoney, 1990; Raine, Venables, & Williams, 1990a, 1990b; van der Molen, Somsen, Jennings, Nieuwboer, & Orlebeke, 1987; Wadsworth, 1976).
