Postpartum Maternal Mood Among Hadza Foragers of Tanzania: A Mixed Methods Approach

What We Can Learn About Emotion by Talking With the Hadza

Emotions are often thought of as internal mental states centering on individuals' subjective feelings and evaluations. This understanding is consistent with studies of emotion narratives, or the descriptions people give for experienced events that they regard as emotions. Yet these studies, and contemporary psychology more generally, often rely on observations of educated Europeans and European Americans, constraining psychological theory and methods. In this article, we present observations from an inductive, qualitative analysis of interviews conducted with the Hadza, a community of small-scale hunter-gatherers in Tanzania, and juxtapose them with a set of interviews conducted with Americans from North Carolina. Although North Carolina event descriptions largely conformed to the assumptions of eurocentric psychological theory, Hadza descriptions foregrounded action and bodily sensations, the physical environment, immediate needs, and the experiences of social others. These observations suggest that subjective feelings and internal mental states may not be the organizing principle of emotion the world around. Qualitative analysis of emotion narratives from outside of a U.S. (and western) cultural context has the potential to uncover additional diversity in meaning-making, offering a descriptive foundation on which to build a more robust and inclusive science of emotion.

The Prevalence of Behavioural Symptoms and Psychiatric Disorders in Hadza Children

The worldwide pooled prevalence of psychiatric disorders in children is 13.4%. Studying the prevalence of childhood psychiatric disorders across radically different economic systems and social structures could indicate universal factors leading to their development. The prevalence of childhood psychiatric disorders in a mixed-subsistence foraging society has not been studied. The Strengths and Difficulties Questionnaire and the Development and Well-Being Assessment were used to compare the prevalence of behavioural symptoms and psychiatric disorders in Hadza children aged 5-16 years (n = 113) to a nationally representative sample from England (n = 18,029) using a cross-sectional study design. Emotional problems, conduct problems and hyperactivity were lower in the Hadza children. Prosocial behaviour and peer problems were higher in Hadza children. 3.6% of Hadza children met the criteria for a psychiatric disorder compared to 11.8% of English children. All psychiatric disorders in Hadza children were co-morbid with autism spectrum disorder. No child from the Hadza group met the criteria for an emotional, behaviour or eating disorder. Further work should study the factors which lead to the different prevalence of psychiatric disorders in Hadza children.

Evidence for an emotional adaptive function of dreams: a cross-cultural study

The function of dreams is a longstanding scientific research question. Simulation theories of dream function, which are based on the premise that dreams represent evolutionary past selective pressures and fitness improvement through modified states of consciousness, have yet to be tested in cross-cultural populations that include small-scale forager societies. Here, we analyze dream content with cross-cultural comparisons between the BaYaka (Rep. of Congo) and Hadza (Tanzania) foraging groups and Global North populations, to test the hypothesis that dreams in forager groups serve a more effective emotion regulation function due to their strong social norms and high interpersonal support. Using a linear mixed effects model we analyzed 896 dreams from 234 individuals across these populations, recorded using dream diaries. Dream texts were processed into four psychosocial constructs using the Linguistic Inquiry and Word Count (LIWC-22) dictionary. The BaYaka displayed greater community-oriented dream content. Both the BaYaka and Hadza exhibited heightened threat dream content, while, at the same time, the Hadza demonstrated low negative emotions in their dreams. The Global North Nightmare Disorder group had increased negative emotion content, and the Canadian student sample during the COVID-19 pandemic displayed the highest anxiety dream content. In conclusion, this study supports the notion that dreams in non-clinical populations can effectively regulate emotions by linking potential threats with non-fearful contexts, reducing anxiety and negative emotions through emotional release or catharsis. Overall, this work contributes to our understanding of the evolutionary significance of this altered state of consciousness.

How a pregnant woman's relationships with her siblings relate to her mental health: a prenatal allocare perspective

BACKGROUND

In cooperatively breeding species, individuals may promote their inclusive fitness through allomothering. Humans exhibit some features of cooperative breeding, and previous studies have focused on allomothering by grandparents and juvenile siblings in the postnatal period. We hypothesize that a pregnant woman's relationships with her siblings (offspring's maternal aunts and uncles) are beneficial for maternal affect in ways that can enhance the siblings' inclusive fitness. Maternal affect during pregnancy is a salient target of allocare given the detrimental effects of antepartum mood disorders on birth and infant outcomes.

METHODOLOGY

We test our hypotheses in a cohort of pregnant Latina women in Southern California (N = 201). Predictor variables of interest include number of siblings a participant has, if she has sisters, frequency of seeing siblings, and frequency of communication with siblings. Outcome variables measuring maternal affect include depression, state anxiety, pregnancy-related anxiety and perceived stress.

RESULTS

Having at least one sister and greater frequency of communication with siblings were associated with fewer depressive symptoms during pregnancy. No significant associations were found between sibling variables and other measures of affect.

CONCLUSION AND IMPLICATIONS

Results suggest that how frequently you communicate with, and not how often you see, siblings could be protective against risk of antepartum depression. Sibling allomothering could impart effects through social-emotional support rather than instrumental support, as a strategy to benefit the prenatal environment in which future nieces and nephews develop. Allomothering may be particularly important in cultural contexts that value family relationships. Future studies should investigate other communities.

Harm Avoidance and Mobility During Middle Childhood and Adolescence among Hadza Foragers

Cross-cultural sex differences in mobility and harm avoidance have been widely reported, often emphasizing fitness benefits of long-distance travel for males and high costs for females. Data emerging from adults in small-scale societies, however, are challenging the assumption that female mobility is restricted during reproduction. Such findings warrant further exploration of the ontogeny of mobility. Here, using a combination of machine-learning, mixed-effects linear regression, and GIS mapping, we analyze range size, daily distance traveled, and harm avoidance among Hadza foragers during middle childhood and adolescence. Distance traveled increased with age and, while male adolescents had the longest daily ranges, average daily distance traveled by each sex was similar. We found few age- or sex-related patterns in harm-avoidant responses and a high degree of individual variation. When queried on the same issues, children and their parents were often in alignment as to expectations pertaining to harm avoidance, and siblings tended to behave in similar ways. To the extent that sex differences in mobility did emerge, they were associated with ecological differences in physical threats associated with sex-specific foraging behaviors. Further, we found no strong association between harm avoidance and mobility. Young Hadza foragers of both sexes are highly mobile, regardless of how harm avoidant they are. Taken together, our findings indicate that the causal arrows between harm avoidance and mobility must be evaluated in ecologically specific frameworks where cultural expectations of juvenile mobility can be contextualized.

Postpartum depression and mother-offspring conflict over maternal investment

BACKGROUND AND OBJECTIVES

As the mother-offspring relationship is central to human reproduction, postpartum depression symptoms are difficult to explain in evolutionary terms. We proposed that postpartum depression might arise as a result of evolutionary mother-offspring conflict over maternal investment, and investigated the association between postpartum depression symptoms, infant night waking, maternal sleep disturbance and breastfeeding frequency.

METHODOLOGY

We conducted a cross-sectional analysis using survey responses at 6 months postpartum from 1598 Finnish mothers. We hypothesized that infant night waking at 6 months postpartum would be associated with postpartum depression symptoms, and that this association would be mediated by maternal sleep disturbance and a higher breastfeeding frequency.

RESULTS

Infant night waking was moderately associated with postpartum depression symptoms, and this association was mediated by maternal sleep disturbance (R 2=0.09). Contrary to our prediction, we found that increased breastfeeding was associated with less postpartum depression symptoms.

CONCLUSIONS AND IMPLICATIONS

We conclude that postpartum depression symptoms might partly be the result of increased maternal fatigue stemming from high offspring demands on maternal investment, but that this is not due to the metabolic strain from increased breastfeeding. Studying postpartum depression from the mother-offspring conflict perspective can potentially improve our understanding of the involved behavioral processes of both mother and offspring, and allow interventions designed to benefit the well-being of both parties. Lay Summary: We proposed that postpartum depression is due to an evolutionary conflict between mother and infant, where the infant tires the mother to delay the arrival of a sibling. We found a link between infant night waking and postpartum depression, mediated by the mother's sleep, but not by breastfeeding frequency.

Difference in Perception of Onset of Old Age in Traditional (Hadza) and Modern (Polish) Societies

Despite relatively clear physiological indicators of old age, little is known about cross-cultural differences in psychological perceptions of the transition to old age. Although recent studies suggest consistency between modern countries, the subjective perception of old age onset in traditional societies remains poorly explored. Therefore, we compared the perception of timing of old age between a traditional tribe of hunter-gatherers (the Hadza) and a Polish sample representing a modern, industrialized population. The results indicate that the Hadza perceive old age onset as being significantly earlier than do the Poles. Furthermore, we found between-gender differences in the Polish sample: men set a lower threshold of old age onset than women. The Hadza showed no between-gender difference. Although the samples were matched for age, a larger proportion of Hadza considered themselves old. We discuss these findings from cultural and demographical perspectives.