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Father Trials: Hormonal and Behavioral Experiments on Prenatal and Postnatal Parenting

Periodic Reporting for period 3 - FATHER TRIALS (Father Trials: Hormonal and Behavioral Experiments on Prenatal and Postnatal Parenting )

Reporting period: 2018-08-01 to 2020-01-31

Fathers have largely been neglected in parenting research -- although they constitute about 50% of parents. In the current project we test the hypothesis that fathers’ parenting is affected by their hormonal levels, and can be changed by behavioral and hormonal interventions.

This project combines two types of experiments (hormonal administration and behavioral intervention), in a critical phase of parenthood: the transition to having the first baby. The focus lies on the 50% of parents who have tended to be neglected in research: fathers.
We observe fathers’ sensitive parenting behavior, a key construct in research on parenting. It refers to the ability to attend to infant signals and to respond promptly and appropriately. Higher levels of parental sensitivity predict more favorable child outcomes, irrespective of cultural or socio-economic context. Although the quantity of time invested in parenting is generally considered less important than quality (“quality time”), it is easy to see that it takes considerable time to get to know an infant, become aware of its preferences, and read its signals. Fathers spend on average less than half as much time in direct one-on-one interaction with their children as mothers, especially in early childhood. For most young fathers, spending more time in interaction with their infant will add to the quality of the interaction. Such an increase in interaction time may also affect their hormonal levels and brain processes.

An additional focus in the current project is on a dimension of parenting that has received considerable attention in animal research but, despite its evolutionary importance, not in studies on humans: protection. Protection is a crucial aspect of human parenting. This is perhaps demonstrated most convincingly when we are confronted with the absence of parental protection, i.e. neglect, or the opposite of parental protection, i.e. child physical abuse.

In this project fathers are observed prenatally and postnatally, both with their own child and using experimentally manipulated infant stimuli and a life-like baby doll. We test the effects of hormonal and behavioral interventions on the processing of infant crying, on protective parenting, and on the quantity and quality of father-child interaction. The aim is both practical and theoretical: Testing the efficacy of the behavioral experimental interventions in boosting fathers’ participation in caregiving activities has clear practical significance (for fathers, mothers, children, and society), while examining the mechanisms is crucial for the development of theory on the interplay between neuroscience and behavior.
Literature reviews were written on the role of oxytocin in parenting (Feldman & Bakermans-Kranenburg, 2017; Van IJzendoorn & Bakermans-Kranenburg, 2016), on fathering (Bakermans-Kranenburg et al., 2019), and on protective parenting (Bakermans-Kranenburg & Van IJzendoorn, 2017a, 2017b). We wrote two meta-analysis, one challenging the challenge hypothesis of the role of testosterone in parenting, and arguing for a more nuanced perspective of testosterone in the context of other hormone systems (Meijer et al., 2019), and one on the neural processing of infant cry sounds, in which for the first time parents and non-parents, and males and females could be compared in a sufficiently large dataset (Witteman et al., 2019). A series of papers on parenting (Rijlaarsdam et al., 2016; Thijssen et al., 2017), oxytocin experiments (Mah et al., 2016; Riem et al., 2017, 2019; Verhees et al., 2018, 2019), and exposure to infant signals (Heckendorff et al., 2016; Riem et al., 2017; Skvortsova et al., 2020) were published, and invited lectures on fathering and video feedback intervention were given (2017, 2018, 2019).

We developed new paradigms to assess protective parenting both on the behavioral and on the neural level, and we developed an app for ambulatory measurement of paternal involvement.

In order to establish a baseline of the use of baby carriers for the baby carrier intervention, we did a survey assessing baby carrier usage in first-time fathers. This had never been done before, implying that such baseline was not available from the literature. Data was collected on 378 fathers. About half of them had experience using a baby carrier, the other half had no experience. Over half of the baby carrier users used it for less than 2 hours per week, suggesting that, for most fathers, the intervention (6 hours of carrying per week for a period of 3 weeks) will result in a substantial increase in infant carrying time.

We demonstrated the role of vasopressin in neural and behavioral responses to infant crying sounds (Thijssen et al., 2018; Alyousefi-van Dijk, 2019), and we showed the influence of the birth of their first child on father’s protective parenting and way they talk about their babies (Van ‘t Veer et al., 2019).

Because we consider the move to open science and preregistration as a very important one, we preregistered our hormone administration study (Witte et al., 2019)

A Dutch website has been launched, presentations on young parents events have been given, and we have disseminated our results among midwifes and organizers of pregnancy courses and ‘daddy-classes’.

Marinus van IJzendoorn (cofinanced) has supported the team as consultant in all phases of the project.
We demonstrated modulation of paternal neural and behavioral responses to infant cry sounds by vasopressin, pointing to a role of vasopressin in human parenting that has rarely been taken into account.

Beyond the proposed or expected research findings are three key issues:
1.Concerning the role of testosterone in human parenting, we showed that the meta-analytical support for the ‘challenge hypothesis’ is equivocal (Meijer et al., 2019). The challenge hypothesis suggests that testosterone levels of adult men rise under conditions of competition and reproductivity. For competitive mating, higher levels of testosterone are favorable, but lower testosterone levels are supposed to be more conducive for caring for offspring. We did find that having a child and displaying more active paternal involvement or higher parenting quality were related to somewhat lower testosterone levels, but the combined effect sizes were small and there is evidence that publication bias might play a role.

2.We developed an empirically based neural model of infant cry perception, and for the first time, we could compare neural processing of infant cry sounds between males versus females, and parents versus non-parents (Witteman et al., 2019). We found involvement of the auditory system, the thalamocingulate circuit, the dorsal anterior insula, the pre-supplementary motor area and dorsomedial prefrontal cortex and the inferior frontal gyrus in infant cry perception, but not of the reward pathway. Structures related to motoric processing, possibly supporting the preparation of a parenting response, were also involved. Females (more than males) and parents (more than non-parents) recruited a cortico-limbic sensorimotor integration network, offering a neural explanation for previously observed enhanced processing of infant cries in these sub-groups.

3.The interest of professionals and the general public in the prenatal video feedback is overwhelming, even before we have results from the RCT.
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