Gert Stulp

• PhD.
• Research Associate at University of Groningen

Uncertainty in fertility intentions is a major obstacle to understanding contemporary trends in fertility decision-making and its outcomes. Quantifying this uncertainty by structural factors such as income, ethnicity, and housing conditions is recognized as insufficient. A recently proposed framework on subjective narratives has opened up a new way...

Passive smartphone measures hold significant potential and are increasingly employed in psychological and biomedical research to capture an individual's behavior. These measures involve the near-continuous and unobtrusive collection of data from smartphones without requiring active input from participants. For example, GPS sensors are used to deter...

The daily social life of a person can be captured with different methodologies. Two methods that are especially promising are personal-social-network (PSN) data collection and experience-sampling methodology (ESM). Whereas PSN data collections ask participants to provide information on their social relationships and broader social environment, ESM...

The social sciences have produced an impressive body of research on determinants of fertility outcomes, or whether and when people have children. However, the strength of these determinants and underlying theories are rarely evaluated on their predictive ability on new data. This prevents us from systematically comparing studies, hindering the eval...

Passive smartphone measures hold significant potential and are increasingly employed in psychological and biomedical research to capture an individual's behavior. These measures involve the near-continuous and unobtrusive collection of data from smartphones without requiring active input from participants. For example, GPS sensors are used to deter...

People's fertility preferences are often considered an important determinant of fertility. What is often neglected in studies of preferred fertility, is the uncertainty that people may have about their preferences. In this study, using data on Dutch women through the Longitudinal Internet studies for the Social Sciences (collected early 2018), we e...

The use of smartphones and wearable sensors to passively collect data on behavior has great potential for better understanding psychological well-being and mental disorders with minimal burden. However, there are important methodological challenges that may hinder the widespread adoption of these passive measures. A crucial one is the issue of time...

Social interactions are essential for well-being. Therefore, researchers increasingly attempt to capture an individual's social context to predict well-being, including mood. Different tools are used to measure various aspects of the social context. Digital phenotyping is a commonly used technology to assess a person's social behavior objectively....

People's networks are considered key in explaining fertility outcomes—whether people want and have children. Existing research on social influences on fertility is limited because data often come from small networks or highly selective samples, only few network variables are considered, and the strength of network effects is not properly assessed....

The daily social life of a person can be captured with different methodologies. Two methods that are especially promising are personal social network (PSN) data collection and experience sampling methodology (ESM). While PSN data collections ask participants to provide information on their social relationships and broader social environment, ESM st...

Background Persecutory delusions are strong threat beliefs about others’ negative intentions. They can have a major impact on patients’ day-to-day life. The Feeling Safe Programme is a new translational cognitive-behaviour therapy that helps patients modify threat beliefs and relearn safety by targeting key psychological causal factors. A different...

The social context of a person, meaning their social relationships and daily social interactions, is an important factor for understanding their mental health. However, personalised feedback approaches to psychotherapy do not consider this factor sufficiently yet. Therefore, we developed an interactive feedback prototype focusing specifically on a...

The Dutch have a remarkable history when it comes to height. From being one of the shortest European populations in the 19th Century, the Dutch grew some 20 cm and are currently the tallest population in the world. Wealth, hygiene, and diet are well-established contributors to this major increase in height. Some have suggested that natural selectio...

Friends are an important source of well-being but people differ in who they consider to be friends. With a unique quantitative test of such differences based on 17,650 social relations of 706 Dutch women (aged 18–41), of whom 40% were considered friends, we examined (a) which kind of personal relations were typically identified as friends (e.g., fa...

Personal network data is increasingly used to answer research questions about the interplay between individuals (i.e., egos) and their social environment (i.e., alters). Researchers designing such data collections face a trade-off: When eliciting a high number of alters, study participation can be particularly burdensome as all data is obtained by...

This study among 725 male and 247 female police officers from The Netherlands examined the association between self-reported height and occupational rank from the perspective of sexual selection. Male and female police officers were taller than the average population. A larger percentage of women than of men was found in the lowest ranks, but in th...

The fertility decline associated with economic development has been attributed to a host of interrelated causes including the rising costs of children with industrialization, and shifts in family structure. One hypothesis is that kin may impart more pro-natal information within their networks than non-kin, and that this effect may be exacerbated in...

In this study we report on our experiences with collecting large personal network data (25 alters) from a representative sample of Dutch women. We made use of GENSI, a recently developed tool for network data collection using interactive visual elements that has been shown to reduce respondent burden. A sample of 758 women between the ages of 18 an...

Background: The age at parenthood has risen by about five years in the last decades in the Netherlands. Previous studies typically focused on the age at which people have their first child, but little is known about desired timing of parenthood and how this desire changes. Objective: In this study, we examined three facets of postponement: (1) desi...

Biological, genetic, and socio-demographic factors are all important in explaining reproductive behavior, yet these factors are typically studied in isolation. In this study, we explore an innovative sociogenomic approach, which entails including key socio-demographic (marriage, education, occupation, religion, cohort) and genetic factors related t...

Although there are well-established relationships between women’s higher education, labour force participation (LFP) and occupation with childlessness, the underlying reasons and the role that fertility desires and expectations play remains unclear. We use the National Longitudinal Survey of Youth in the United States (N=4,198 women). We apply both...

In this commentary, we consider how evolutionary biology’s life history theory(LHT) can be integrated with life course theorizing, to the benefit of both endeavors. We highlight areas where it can add value to existing work in life course theory (LCT), focusing on: how it can add an extra level of explanation, which may be helpful in understanding...

This chapter discusses briefly why studies in behavioural genetics seem to fuel the nature‐nurture debate. It considers how evolutionary thinking can help improve our understanding of human behaviour, as well as shows why non‐evolutionary thinking can sometimes go awry. The chapter uses a few key examples to illustrate the value of evolutionary thi...

Although the term “evolutionary psychology” would appear both simple and self‐explanatory, suggesting a rather straightforward application of evolutionary theory to both human and nonhuman psychology, appearances can be deceptive. The status of the discipline and its recent history are far from straightforward, and debates between various schools o...

Meta-analyses of genome-wide association studies (GWAS), which dominate genetic discovery are based on data from diverse historical time periods and populations. Genetic scores derived from GWAS explain only a fraction of the heritability estimates obtained from whole-genome studies on single populations, known as the 'hidden heritability' puzzle....

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Is fertility relevant to evolutionary analyses conducted in modern industrial societies? This question has been the subject of a highly contentious debate, beginning in the late 1980s and continuing to this day. Researchers in both evolutionary and social sciences have argued that the measurement of fitness-related traits (e.g., fertility) offers l...

Studies of the association between wealth and fertility in industrial populations have a rich history in the evolutionary literature, and they have been used to argue both for and against a behavioral ecological approach to explaining human variability. We consider that there are strong arguments in favor of measuring fertility (and proxies thereof...

Objectives: The study of assortative mating for height has a rich history in human biology. Although the positive correlation between the stature of spouses has often been noted in western populations, recent papers suggest that mating patterns for stature are not universal. The objective of this paper was to review the published evidence to exami...

Fertility behavior – such as age at first birth and number of children – varies strongly across historical time and geographical space. Yet, family and twin studies, which suggest that up to 50% of individual differences in fertility are heritable, implicitly assume that the genes important for fertility are the same across both time and space. Usi...

The lack of association between wealth and fertility in contemporary industrialized populations has often been used to question the value of an evolutionary perspective on human behaviour. Here, we first present the history of this debate, and the evolutionary explanations for why wealth and fertility (the number of children) are decoupled in moder...

Variation in fertility patterns in relation to environmental factors and mortality schedules can be understood using evolutionary life history theory (LHT). In addition to explaining differences within and between human populations, LHT allows us to make direct comparisons with other species. Here we discuss LHT, the concept of trade-offs, and the...

Heterosexual age preferences have been extensively studied by evolutionary psychologists, social psychologists, and demographers. Much less is known about such preferences in homosexual men and women. Around two decades ago, D. T. Kenrick, R. C. Keefe, A. Bryan, A. Barr, and S. Brown (1995) examined heterosexual and homosexual mating preferences fo...

Many thanks to Bryant (2015) for keeping the conversation lively, and engaging in further debate on our paper (Barrett et al., 2014). Although Bryant raises several interesting points, it appears that, as with our previous commentators, there was some misunderstanding of our aim, which simply was to answer the question posed for us: does evolutiona...

Research on genetic influences on human fertility outcomes such as number of children ever born (NEB) or the age at first childbirth (AFB) has been solely based on twin and family-designs that suffer from problematic assumptions and practical limitations. The current study exploits recent advances in the field of molecular genetics by applying the...

The Dutch are the tallest people on earth. Over the last 200 years, they have grown 20 cm in height: a rapid rate of increase that points to environmental causes. This secular trend in height is echoed across all Western populations, but came to an end, or at least levelled off, much earlier than in The Netherlands. One possibility, then, is that n...

We thank Klasios (2014)1 and Stephen et al. (2014)2 for their commentaries on our paper (Barrett et al., 2014)3. Criticisms like these can only help to improve the quality of arguments offered on both sides. Both Klasios's and Stephen et al.'s commentaries generate misconceptions, however, about the aim of our article and our stated position. Befor...

Body height influences human mate preferences and choice. A typical finding in Western societies is that women prefer men who are taller than themselves and, equivalently, men prefer women who are shorter than themselves. However, recent reports in non-Western societies (e.g., the Himba in Namibia) challenge the view on the universality of such pre...

Field data often include multiple observations taken from the same individual. In order to avoid pseudoreplication, it is commonplace to aggregate data, generating a mean score per individual, and then using these aggregated data in subsequent analyses. Aggregation, however, can generate problems of its own. Not only does it lead to a loss of infor...

Across cultures, taller stature is linked to increased social status, but the potential reasons why this should be are unclear. One potential explanation is that taller individuals are more likely to win a dyadic confrontation with a competitor (i.e., they are more dominant), which leads to higher social rank. Although some previous studies have sh...

Human height is a highly variable trait, both within and between populations, has a high heritability, and influences the manner in which people behave and are treated in society. Although we know much about human height, this information has rarely been brought together in a comprehensive, systematic fashion. Here, we present a synthetic review of...

Does evolutionary theorizing have a role in psychology? This is a more contentious issue than one might imagine, given that, as evolved creatures, the answer must surely be yes. The contested nature of evolutionary psychology lies not in our status as evolved beings, but in the extent to which evolutionary ideas add value to studies of human behavi...

Objectives Although male height is positively associated with many aspects of mate quality, average height men attain higher reproductive success in US populations. We hypothesize that this is because the advantages associated with taller stature accrue mainly from not being short, rather than from being taller than average. Lower fertility by shor...

A study among 1,881 adolescents (52.3% girls) with a mean age of 19.1 years examined the effects of parental social status upon intrasexual competitiveness. Whereas females were consistently more intrasexually competitive the higher the socio-economic status of their parents, males with parents of the lowest socio-economic status tended to be more...

Previous research has shown repeatedly that human stature influences mate preferences and mate choice in heterosexuals. In general, it has been shown that tall men and average height women are most preferred by the opposite sex, and that both sexes prefer to be in a relationship where the man is taller than the woman. However, little is known about...

Media reports often emphasize how the height of US presidential candidates plays an important role in election outcomes, with taller candidates winning an overwhelming number of elections across time. These claims are, however, rarely backed up by any form of reliable statistical analysis. Even when statistical methods are employed, they are often...

ABSTCT Tinbergen's paper on aims and methods in ethology is, quite rightly, a citation classic. Here, we would like to emphasize that, 50 years aer its initial publication, it continues to offer esh insights into study of ethology – and human ethology in particular – as well as offering a valuable historical perspective on the biology of behavior m...

Telomere length and the rate of telomere attrition vary between individuals and have been interpreted as the rate at which individuals have aged. The biology of telomeres dictates shortening with age, although telomere elongation with age has repeatedly been observed within a minority of individuals in several populations. These findings have been...

Given the heritability of human left-handedness and its purported associations with fitness-lowering traits, the persistence of the minority of left-handedness in human populations is an evolutionary puzzle. The fighting hypothesis proposes that these negative fitness costs are offset by fitness gains for left-handers when involved in fights with r...

a b s t r a c t Physical characteristics, such as height, play an important role in human mate preferences. Satisfaction with one's own height and one's partner height seem likely to be related to these preferences. Using a student sample (N = 650), we show that women are not only more selective, but also more consistent, than men, in their partner...

Mutual mate choice is prevalent in humans, where both males and females have a say in their choice of partner. How the choices made by one sex constrain the choice of the other remains poorly understood, however, because human studies have mostly limited themselves to measuring preferences. We used a sample of 5782 speed-daters making 128 104 choic...

The majority of research examining sex differences in risk-taking behavior focuses on overt physical risk measures in which failed risk attempts may result in serious injury or death. The present research describes sex differences in patterns of risk taking in day-to-day behavior among Dutch cyclists. Through three observational studies we test sex...

A common stereotype is that richer men have wives who are substantially younger than themselves. However, some research suggests that large age gaps are actually more common with low male income, at least in the general population. Here, we examine spousal age differences among the super wealthy (Forbes 400 list – the richest 400 individuals in the...

Pair formation, acquiring a mate to form a reproductive unit, is a complex process. Mating preferences are a step in this process. However, due to constraining factors such as availability of mates, rival competition, and mutual mate choice, preferred characteristics may not be realised in the actual partner. People value height in their partner an...

Male facial width-to-height ratio (bizygomatic width scaled for face height) is a testosterone-linked trait predictive of reactive aggression, exploitative behavior, cheating, deception, and dominance. We tested whether facial width was systematically related to cause of death in a forensic sample. We hypothesized that wider-faced males, being more...

Theoretical analyses and empirical studies have revealed that conflict escalation is more likely when individuals are more similar in resource-holding potential (RHP). Conflicts can also occur between groups, but it is unknown whether conflicts also escalate more when groups are more similar in RHP. We tested this hypothesis in humans, using data f...

Intralocus sexual conflict (IASC) occurs when a trait under selection in one sex constrains the other sex from achieving its sex-specific fitness optimum. Selection pressures on body size often differ between the sexes across many species, including humans: among men individuals of average height enjoy the highest reproductive success, while shorte...

In this article we examine the association between female height and reproductive success in a US sample and present a review of previous studies on this association. We also outline possible biological explanations for our findings. We used data from a long-term study of 5,326 female Wisconsin high school graduates to examine the association betwe...

Throughout the animal kingdom, larger males are more likely to attain social dominance. Several lines of evidence suggest that this relationship extends to humans, as height is positively related to dominance, status and authority. We hypothesized that height is also a determinant of authority in professional refereeing. According to the Internatio...

Human male height is associated with mate choice and intra-sexual competition, and therefore potentially with reproductive success. A literature review (n = 18) on the relationship between male height and reproductive success revealed a variety of relationships ranging from negative to curvilinear to positive. Some of the variation in results may s...

Model predictions for the effect of maternal height on the risk (%) of an emergency Caesarean section for mothers carrying low (mean − s.d.), average (mean) and high (mean + s.d.) birth weight newborns. (TIF)

Model predictions for the effect of parental height differences on the risk (%) of an emergency Caesarean section for short (mean− s.d.), average (mean) and tall (mean + s.d.) mothers carrying an average birth weight newborn. (TIF)

Characteristics (mean ± standard deviation or %) of the sample used for our analyses. (DOC)

Logistic regression parameter estimates (± s.e.) of the effects of maternal height, height2, parental height differences (PHD), birth weight, their interactions, and control variables on the probability of an emergency Caesarean section. (DOC)

Model predictions for the risk (%) of an emergency Caesarean section for short, average height, and tall mothers with small, average and large parental height differences (PHD). (DOC)

Logistic regression parameter estimates (± s.e.) of the effects of maternal height (cm), height2, birth weight (kg), birth weight2, parental height differences (cm) and their interactions, on the probability of an emergency Caesarean section when light birth weight newborns (<2.5 kg) are excluded. (DOC)

Model predictions for the risk (%) of an emergency Caesarean section for low (mean − s.d.), average (mean) and high (mean + s.d.) birth weight newborns having (a) short (mean − s.d.), average height (mean), and tall (mean + s.d.) mothers and (b) small (mean − s.d.), average (mean), and large (mean + s.d.) parental height differences for short, aver...

Model predictions for the effect of parental height differences on the risk (%) of an emergency Caesarean section for average height mothers carrying low (mean − s.d.), average (mean) and high (mean + s.d.) birth weight newborns. (TIF)

More than 30% of all pregnancies in the UK require some form of assistance at delivery, with one of the more severe forms of assistance being an emergency Caesarean section (ECS). Previously it has been shown that the likelihood of a delivery via ECS is positively associated with the birth weight and size of the newborn and negatively with maternal...

Western scrub-jays (Aphelocoma californica) engage in a variety of cache-protection strategies to reduce the chances of cache theft by conspecifics. Many of these strategies revolve around reducing visual information to potential thieves. This study aimed to determine whether the jays also reduce auditory information during caching. Each jay was gi...

In this paper we report on experiments to determine if antonymy is a good predictor of contrast, using 124 texts from the British National Corpus and the antonymy relations for adjectives recognized by WordNet. Further, we considered whether antonyms are key arguments in the inferences that license contrast. We looked at the frequency of both indir...