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Fathers who hold more traditional beliefs about masculinity tend to experience a sharper drop in testosterone while spending one-on-one time with their preschool-aged children, according to a new study published in Hormones and Behavior. Although popular belief often links traditional manhood with high testosterone, the findings indicate that men’s beliefs about gender roles are not tied to their baseline hormone levels. Instead, holding traditional views on masculinity is linked to how strongly a father’s testosterone shifts when he steps into a solo caregiving role.
Testosterone is a steroid hormone produced primarily in the testes, and in smaller amounts in the ovaries and adrenal glands, that helps regulate physical development, reproduction, and social behavior. In everyday conversation, the hormone is frequently equated with masculinity, dominance, and aggression. However, previous analyses have found that a man’s baseline, resting testosterone levels are not linked to having masculine facial features or competitive personality traits. This study took a different approach, focusing on traditional masculinity ideology, which is a belief system holding that men should conform to strict gender norms such as toughness, emotional control, self-reliance, and the avoidance of stereotypically feminine behaviors like nurturing.
Although baseline hormone levels have not been linked to measures of masculinity, hormone levels do fluctuate temporarily in response to social situations, a process known as hormone reactivity. In biology, the Challenge Hypothesis proposes that testosterone rises to support competition and mating efforts, and drops to shift energy toward nurturing offspring. Consistent with this framework, an observational study of men across different living arrangements found that partnered men living with school-aged children or teenagers had lower testosterone than single men or partnered men without children, though these lower levels were not more likely to fall into the clinically deficient range.
Building on this idea, the Steroid/Peptide Theory of Social Bonds, a framework lead author Patty X. Kuo helped develop, suggests that specific parenting situations trigger different short-term hormone shifts: comforting a distressed child tends to lower testosterone, whereas protecting a child from a threat or competing with others can cause testosterone to rise.
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Because parenting involves both tender care and firm boundary-setting, the researchers reasoned that a father’s psychological outlook could influence how his body responds to his child. For example, an earlier laboratory study of parents and their 1-year-olds, co-authored by Kuo, found that fathers’ testosterone generally fell after a stressful separation-and-reunion task, but fathers who were uncomfortable with emotional closeness showed smaller declines.
Most hormone research on fatherhood has focused on infants and toddlers, leaving less known about the preschool years, when children are between 3 and 5 years old. During this stage, children still require warmth and reassurance, but they also push for independence and act out more often, requiring parents to balance nurturing with discipline.
“There is an interest in masculinity and testosterone both societally and empirically,” Kuo, an associate professor of child, youth and family studies at the University of Nebraska-Lincoln and director of the Nebraska Strong Families Lab, told PsyPost. “However, masculinity is often measured through proxies – such as ascribing certain types of features (square jaw) or behaviors (aggression) as ‘masculine’ instead of using a shared conceptual definition of masculinity. Here, we used traditional masculinity ideology – which reflects people’s beliefs about how men should think, feel, and act.”
“This sample of fathers is also interesting to study when it comes to masculinity and testosterone because there is this well-known theory called the ‘Challenge Hypothesis’, which proposes that testosterone decreases in males can facilitate parenting behavior,” Kuo explained. “So men actually decrease in testosterone when they become fathers, but US society has also made ‘low T’ a problem, at least according to some. I wanted to put all of these pieces together to see what we could learn about testosterone and masculinity ideology among fathers.”
Specifically, Kuo and her colleagues wanted to know whether a father’s beliefs about masculinity would be linked to his short-term testosterone changes while interacting with his preschooler. Because traditional masculinity norms often frame childcare and emotional warmth as feminine responsibilities, a father who strongly endorses these norms might evaluate and react to parenting tasks differently than a more egalitarian father. The researchers hypothesized that fathers with more traditional beliefs about masculinity would be less inclined toward nurturing behaviors, resulting in smaller drops, or even increases, in testosterone while interacting with their children.
To test this idea, the researchers recruited 42 fathers and their 3- to 5-year-old children, nearly evenly split between boys and girls, from the Midwestern United States between February 2020 and July 2023. The fathers ranged from 24 to 52 years old, with an average age of about 37; most were white, and nearly all were married and employed full-time. Before visiting the laboratory, the fathers completed an online survey that measured their endorsement of traditional masculinity ideology. They rated their agreement on a 1-to-7 scale with five statements about how men should behave, such as the belief that men should not be too quick to tell others that they care about them.
The fathers also reported how childcare was divided in their homes: about 44% said the child’s mother was the primary caregiver, 33% reported sharing caregiving equally, and 22% identified themselves as the primary caregiver. Each father then attended a one-hour laboratory session alone with his preschooler and collected his own saliva samples using oral swabs at three points to track short-term testosterone reactivity. The first saliva sample was taken about 15 minutes after arrival to establish a baseline level. Next, the father and child participated in a 25-minute separation-and-reunion exercise designed for preschoolers, which included periods of free play with toys interrupted by two brief 5-minute separations where the father left the room and watched his child through a two-way mirror before returning.
Immediately after the separation-and-reunion exercise, the fathers provided a second saliva sample. The pair then moved on to a 20-minute clean-up and teaching session designed to assess parenting under moderately challenging conditions. Fathers first had to instruct their child to put all the toys away in a bin within 5 minutes without physically helping them. After cleaning up, the fathers spent 15 minutes teaching their child how to complete three difficult puzzles that were too advanced for a preschooler to solve alone, again without physically touching the pieces, before providing a third and final saliva sample.
When the researchers analyzed the saliva samples across the entire group of 42 men, average testosterone levels did not significantly change from the beginning to the end of the laboratory visit. Across all participants, testosterone dropped by an average of 2.46% after the separation task, a group-wide shift that was not statistically significant, and individual fathers’ responses varied widely, with some rising and others falling. This differs from a 2016 study led by Kuo that used a similar procedure with infants, where fathers’ testosterone fell during the separation-and-reunion task but did not significantly change during a later teaching task. The authors suggest the current study found no group-wide drop because preschoolers are better able to manage their emotions and are less likely than infants to become intensely distressed during brief separations.
The authors note that even small short-term shifts can exceed the roughly 1.6% decline men show over a year of aging, though they caution that without other physical measurements, it is hard to know whether changes of this size matter physically. In line with prior research, a father’s baseline testosterone level at the start of the visit had no statistically significant link to his beliefs about masculinity.
However, when the researchers looked at how each father’s hormone levels changed over the session, they found the opposite of what they had predicted. Using a statistical model that controlled for the time of day, laboratory testing batch, and whether the father was the primary caregiver, the authors found that stronger traditional masculinity beliefs predicted steeper drops in testosterone, a moderate relationship. Masculinity beliefs alone accounted for roughly 15% to 18% of the variation in hormone changes.
The fathers’ average score was 2.98, below the scale’s midpoint of 4, so the group as a whole leaned away from traditional norms, and “more traditional” here is relative. For every one-point increase on the scale, a father’s testosterone dropped by an additional 5.99% between baseline and the end of the separation task, and by 7.28% from baseline to the end of the puzzle task. Masculinity beliefs were not significantly linked to hormone changes between the second and third samples, suggesting the link was concentrated in the first part of the visit.
“Being a ‘high T’ man does not mean that you are more (or less) masculine,” Kuo said. “Men’s testosterone fluctuates according to the situations that we are in – including interacting with their children. The men who self-reported having more traditional masculine ideals actually decreased in testosterone while interacting with their children more than the men who had less traditional masculine ideals.”
The researchers also uncovered a notable pattern when looking directly at who handled the bulk of childcare at home. Before adjusting for masculinity beliefs and other variables, the nine fathers who identified as their child’s primary caregiver, whose individual hormone responses varied widely, showed an average testosterone increase of 8.46% after the separation task, compared with an average decrease of 9.52% among the 14 fathers who shared caregiving equally.
Across the full visit, primary-caregiver fathers showed an average increase of 5.52% compared with an 11.71% decrease among equal-caregiving fathers, though this full-visit difference was not statistically significant. When primary caregiver status was placed into the larger statistical model alongside masculinity beliefs, its link with testosterone change was no longer statistically significant, which the authors attribute to the small sample.
To explain why fathers with more traditional views on manhood experienced larger drops in testosterone, the authors pointed to the possible unfamiliarity of the situation. The authors note that men with traditional beliefs may be more likely to view day-to-day childcare as a mother’s responsibility and take a more secondary role at home. For these fathers, being alone with their preschooler in an unfamiliar room without their partner present may have been a novel experience that required them to step out of a traditional protector role and into a nurturing one. That possible shift into solo caregiving could have triggered a stronger biological adjustment, reflected in a sharper drop in testosterone.
The authors suggest that fathers who already serve as primary caregivers may be more accustomed to managing their children alone, making the laboratory visit feel more routine. Because primary caregivers are frequently responsible for day-to-day discipline and managing stubborn behavior in preschoolers, the researchers propose they may have approached the tasks with an eye toward keeping their child on track, a mindset that theoretical models predict would maintain or slightly raise testosterone. Meanwhile, fathers who share caregiving equally or play a secondary role may have perceived a greater need to provide comforting and nurturing care during the visit, which theory predicts would cause testosterone to fall. However, the study did not measure how novel the visit felt to each father or how they viewed their role during the tasks.
As with all research, there are some caveats to consider when interpreting these results, and the authors describe their work as a preliminary study whose findings need replication in a larger sample. Because the main result ran opposite to the researchers’ initial hypothesis, their explanation involving the novelty of solo caregiving was developed after seeing the data. The correlational design also cannot show that masculinity beliefs directly cause hormone changes.
The study relied on a relatively small sample of 42 fathers who were mostly white, married, college-educated, and living in the Midwest, which limits how well the findings apply to single fathers or families from different cultural and economic backgrounds. With a sample of this size, the statistical analyses could reliably detect medium-to-large effects but may have missed subtler relationships.
In addition, the study did not report how fathers actually behaved during the tasks, leaving open whether men with dropping testosterone acted more warmly or less dominantly toward their children, and a single one-hour laboratory visit cannot show how a father’s hormones fluctuate across a normal day at home.
Future studies with larger, more diverse groups of fathers could examine fathers’ actual parenting behaviors and subjective perceptions alongside measurements of stress hormones like cortisol, which some researchers propose works together with testosterone to shape how parents respond to challenging situations. Even with these limitations, the findings challenge common stereotypes that equate traditional masculinity with elevated testosterone, suggesting instead that a father’s beliefs about manhood are linked to how his testosterone responds to caring for a young child.
The study, “Traditional masculinity ideology enhances testosterone reactivity in human fathers of preschoolers,” was authored by Patty X. Kuo, Maxwell Lottes, Jiabin Lyu, and Ali E. Shull.
