Sensation seeking in fathers: The impact on testosterone and paternal investment Tiziana Perini, Beate Ditzen, Michael Hengartner, Ulrike Ehlert ⁎ Department of Psychology, Clinical Psychology and Psychotherapy, University of Zurich, CH-8044 Zurich, Switzerland abstract article info Article history: Received 14 July 2011 Revised 7 December 2011 Accepted 7 December 2011 Available online 14 December 2011 Keywords: Testosterone Sensation seeking Father Transition to fatherhood Paternal investment Paternal care Mating behavior Diurnal fluctuation Paternal care is associated with a reduced likelihood of engaging in competitive or mating behavior and an increased likelihood of providing protection when necessary. Over recent years, there has been increasing ev- idence to assume that the steroid testosterone (T) in men might reflect the degree of mating effort. In line with this, decreased T levels were shown in fathers compared to non-fathers and it was suggested that pater- nal care, and most behavior positively associated with T, might be incompatible with each other. Indepen- dently, the personality trait sensation seeking (SS) has been related to mating behavior and also to elevated T in men. Aiming to integrate these different lines of research in a longitudinal approach, we ex- plored the impact of SS on T levels in the context of the transition to fatherhood. Thirty-seven fathers and 38 men without children but in committed, romantic relationships (controls) were recruited. At two time points (for fathers: four weeks prior to (t1) and eight weeks after birth (t2)), all subjects repeatedly collected saliva samples for T measurement, filled in a protocol of activities during the course of these days and com- pleted an online questionnaire. In line with our hypotheses, the results show significantly lower aggregated (AUC-T) T levels in fathers compared with non-fathers. Furthermore, moderation analyses revealed a signif- icant interaction between group and SS at t2, with the lowest T levels in low SS fathers. These data suggest that adaptation processes of the transition to fatherhood are influenced by individual differences in person- ality traits. © 2011 Elsevier Inc. All rights reserved. Introduction Parenting effort and personal father–child interactions have sig- nificantly increased in fathers in Western societies, and more recent- ly, research has turned towards the biological correlates of reproductive strategies in men (Alvergne et al., 2009; Berg and Wynne-Edwards, 2001; Storey et al., 2000; reviewed in Kentner et al., 2010). In animal research, biological determinants of fathering have been well established over recent years. For example, as early as 1990, Wingfield et al. described the challenge hypothesis in mo- nogamous bird species, which stands for a trade-off between mating effort and parenting effort. Mating effort includes mate attraction, male–male competition and aggression during reproductive phases, whereas paternal effort means the time and energy which males spend on caring for their offspring (see also Wingfield et al., 2001). There are large differences in reproductive strategies between spe- cies. For example, in mammals with few offspring, paternal invest- ment can be intense in order to enhance the offspring's survival rates. Most species with intense paternal investment are monoga- mous and, as a consequence, research has turned towards the neuro- biological underpinnings of paternal investment in monogamous vs. polygamous mammals, including humans (c.f., Alvergne et al., 2009; Geary, 2000). This research suggests that particularly the steroid tes- tosterone (T) might be involved in the trade-off between mating and parenting effort, as T is positively associated with mating effort (McGlothlin et al., 2007; Muller et al., 2009) and negatively related to bond maintenance and paternal care (Numan and Insel, 2003; Wynne-Edwards and Reburn, 2000). Levels of T were found to be lower in partnered men than in singles (Booth and Dabbs, 1993; Gray et al., 2002; Mazur and Michalek, 1998) and lowest in fathers who are actively engaged in child care (Berg and Wynne-Edwards, 2001; Gettler et al., 2011; Storey et al., 2000). Interestingly, in the lat- ter, T was triggered by specific stimuli such as infant cries (Fleming et al., 2002; Storey et al., 2000). This is in line with the behavioral modulation of T over the course of the day (Muller et al., 2009), in which morning T levels might reflect endogenous physiology (Gray et al., 2007), whereas afternoon and evening T levels might be influenced by behavior and so- cial contacts (for a review, see Eisenegger et al., 2011). From a different perspective, personality traits, such as antisocial per- sonality and sensation seeking (SS), have been discussed in relation to T in humans. SS is defined as “… seeking for varied, novel, complex, and intensive sensations and experiences, and the willingness to take physical, social, legal and financial risks for the sake of such experiences.” (Zuckerman, 1994; p. 27). SS is positively associated with T, and greater diurnal variation in T in high sensation seekers has been reported (Bogaert and Fisher, 1995; Daitzman and Zuckerman, 1980; Daitzman et al., 1978; Gerra et al., 1999; but see also Rosenblitt et al., 2001; Wang Hormones and Behavior 61 (2012) 191–195 ⁎ Corresponding author at: University of Zurich, Department of Clinical Psychology and Psychotherapy, Binzmuehlestrasse 14/Box 26, CH-8050 Zurich, Switzerland. Fax: +41 44 6357359. E-mail address: u.ehlert@psychologie.uzh.ch (U. Ehlert). 0018-506X/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.yhbeh.2011.12.004 Contents lists available at SciVerse ScienceDirect Hormones and Behavior journal homepage: www.elsevier.com/locate/yhbeh