Fleming, A. S., Corter, C., Stallings, J., & Steiner, M. (2002). Testosterone and prolactin are associated with emotional responses to infant cries in new fathers. Hormones and Behavior, 42(4), 399-413.

To determine the responsiveness of new fathers and non-fathers toward infant cues, we exposed fathers and non-fathers to infant cries and to control stimuli and we measured affective, heart-rate, and endocrine responses, including salivary testosterone and cortisol and plasma prolactin concentrations prior to and after cry presentations. We found that

(1) fathers hearing the cry stimuli felt more sympathetic and more alert compared to groups who did not hear the cries or to non-fathers who heard the cries;

(2) fathers and non-fathers with lower testosterone levels had higher sympathy and/or need to respond to the infant cries than fathers with higher testosterone levels;

(3) fathers with higher, as opposed to lower, prolactin levels were also more alert and more positive in response to the cries;

(4) fathers hearing the cry stimuli showed greater percentage increase in testosterone than fathers not hearing the cry stimuli;

(5) experienced fathers hearing the cries showed a greater percentage increase in prolactin levels compared to first-time fathers or to any group of fathers hearing control stimuli; finally,

(6) partial correlations with parity and experience entered as a covariates indicated that both experience and testosterone contributed to the variance in fathers' affective responses to infant cries.

Taken together, these results indicate that, as with a number of other biparental species, human fathers are more responsive to infant cues than are non-fathers and fathers' responses to infant cues are related to both hormones and to caregiving experience. (C) 2002 Elsevier Science (USA).

Burnham, T. C., Chapman, J. F., Gray, P. B., McIntyre, M. H., Lipson, S. F., & Ellison, P. T. (2003). Men in committed, romantic relationships have lower testosterone. Hormones and Behavior, 44(2), 119-122.

Variation in human male testosterone levels may reflect, and effect, differential behavioral allocation to mating and parenting effort. This proposition leads to the hypothesis that, among North American men, those involved in committed, romantic relationships will have lower testosterone levels than men not involved in such relationships. Our study is the first to examine whether being in such a relationship (rather than being married) is the meaningful predictor of male testosterone levels. To test this hypothesis, 122 male Harvard Business School students filled out a questionnaire and collected one saliva sample (from which testosterone level was measured). Results revealed that men in committed, romantic relationships had 21% lower testosterone levels than men not involved in such relationships. Furthermore. the testosterone levels of married men and unmarried men who were involved in committed, romantic relationships did not differ, suggesting that, at least for this sample, male pair bonding status is the more significant predictor of testosterone levels than is marital status. (C) 2003 Elsevier Inc. All rights reserved.

Schradin, C., & Anzenberger, G. (1999). Prolactin, the hormone of paternity. News in Physiological Sciences, 14, 223-231.

Prolactin has long been known to play a significant role in maternal care. When behavioral endocrinologists began to examine the endocrinology of fatherhood, prolactin was also found to be connected with paternal care in fish, birds, and mammals including primates.