Researchers believe that leading up to the birth of their children, men’s brains become more plastic (Martínez-García et al., 2022). In other words, fathers who more often seek physical closeness with their infants will be more inclined to seek physical closeness in the future, particularly after hearing their infant cry. These temporary peaks in cortisol help fathers rapidly detect and respond to infant distress. When fathers hear an infant crying (not necessarily their own), their bodies produce more cortisol (Fleming et al., 2002)—a hormone that is produced in stressful situations. Profoundly, the biological effects of fatherhood heavily depend on the extent that fathers are involved in caregiving, which has notably changed over the last several decades. "Low testosterone during the postpartum period may be a normal and natural adaptation to parenthood." If they were paired with lower-testosterone partners, women reported greater satisfaction with their relationship, which in turn helped reduce their depressive symptoms. Testosterone levels naturally fluctuate throughout the day, typically peaking in the morning. The researchers adjusted their statistical models to account for the time of day the blood was drawn. To measure testosterone, the survey used serum samples analyzed via liquid chromatography tandem mass spectrometry. The final sample included 4,903 men between the ages of 20 and 60. The study analyzed data from three different waves of the survey collected between 2011 and 2016. They wanted to know if these naturally occurring dips in testosterone place men at risk for a medical condition known as androgen deficiency. For example, in marriages, husbands’, but not wives’, testosterone is positively related to marital quality when his role overload is low, but negatively related to marital quality when his role overload is high (Booth et al., 2005). For example, research on men has consistently found a link between concentrations of testosterone and behaviors that may influence family life. These studies indicate that hormones and parent-child relations are linked at all stages of child development. For example, hormones have become central in explaining parent-infant attachment (Fleming et al., 1997; Uvnas-Moberg, 1997), risk and resilience in early child development (Cairns et al., 1990; Gottlieb, 1992; Curtis and Cicchetti, 2003), and hormone related adolescent problem behavior moderated by parent-child closeness (Booth et al., 2003). While testosterone levels are important, they should be considered within the broader context of social support, personal beliefs, and cultural norms. The Parenting Stress Index (PSI; Abidin, 2012) Role Restriction is a subscale of the PSI, a self-report measure of perceived stress from parenting. During the novelty task, an assistant wearing a costume (e.g., "Shrek," first parent-child interaction, "Sulley" from Monsters, Inc., second interaction) entered the room and gradually approached the child within 2 feet while delivering a standard script. During caregiving, parents were asked to undress the infant, change the infants’ diaper, and redress the infant. Across several samples of varying risk, ReACCT Noncompliance scores demonstrated reliability and correlated with measures of abuse risk (CAPI, AAPI-2) and harsh and abusive physical discipline (Rodriguez, 2016). Because the child may have been noncompliant, the parent can remain "stuck" in a scene until the child complies; thus, the parent provides 20 total discipline responses across the 12 scenes. Parents are asked to select from 16 possible options how they would respond to the child’s compliance or noncompliance; some parent responses are adaptive (receiving positive weights) versus maladaptive (receiving negative weights)—e.g., physical and psychological aggression. In each scene, the parent is told they provided an instruction to the child to get ready to leave home and the child is reported to be either compliant or noncompliant. The Response Analog to Child Compliance Task (ReACCT; Rodriguez, 2016) is a computerized analog task to assess child abuse risk, administered at all four time points. A single sample of saliva (later assayed for testosterone) was collected from parents before beginning a parent-child interaction task. Expectant parents were recruited for the Triple-F study with flyers distributed at local hospital obstetric/gynecological clinics and childbirth classes. Given prior research, we anticipated main effects for lower SES, higher stress from the parenting role, and lower emotion regulation to relate to abuse risk. In the current study, we employed a multimethod approach, including explicit self-report measures, analog tasks, and parent-child interactions. Contemporary theorists speculate that socioeconomic influences can moderate associations between testosterone and antisocial behavior (Yildirim & Derksen, 2012a) wherein aggressive behavior may be expressed when higher testosterone levels interact with lower, rather than higher, SES. Surprisingly, empirical work examining the role of individual differences in testosterone in relation to child abuse risk is absent. Some fathers don't respond to parenthood with the same level of Testosterone suppression, which can lead to increased feelings of frustration and aggression toward the child. It would also be advantageous to consider these measures across a longer period of time to determine whether an alternate explanation is at work here—in particular whether the spillover identified was due to a stable or transient rise in testosterone among mothers. Including such families would add much to our knowledge regarding hormones and parent-child relationship quality. As a result the child who reports on parent-child closeness may be less informed of the problems the mother is having with the father, making the woman’s perceptions of the marriage weakly correlated with the child’s view. Fathers of infants were defined as men whose youngest child was older than 1 mo of age but less than 1 y old. Fathers were defined as men who reported having one or more biological children. Data were collected in 2005 and 2009 as part of the CLHNS, a representative population-based birth cohort study of mothers and their infants born in 1983–1984 (61). They also add to evidence that human males have an evolved neuroendocrine architecture shaped to facilitate their role as fathers and caregivers as a key component of reproductive success. These results point to an important role of the hypothalamic-pituitary-gonadal axis as a mediator of the tradeoff between investments in parenting and mating in human males, similar to what is seen in other species in which paternal care is common. Single nonfathers with higher T at baseline were more likely to be partnered fathers 4.5 y later. The gender distinctions in significant findings may be due to differences in the way testosterone operates in men’s and women’s bodies. What is less clear from our models is why high testosterone men do not experience greater levels of spillover than low testosterone men. Similarly, because women receive more social conditioning then men to portray the role of an ideal spouse they may work harder than men to hide their negative feelings from children.