Letters To A Spanish Youngster CCXLI

Letters To A Spanish Youngster CCXLI

[...]

Your Honor of the great fire in the heart,

L'amour, la tendresse, la gratitude que j'ai pour toi,* dear human but also archangelical being, are so big that sometimes I feel "desamparé... sans direction"*.

I remember well my anguish every day after losing sight of You when You were at my company's headquarters, high priestess... The writer said*:

Chaque foi que je te quitte, j'ai une angoisse et un tremblement au fond du coeur. Où es-tu ? Où es-tu, mon amour ? Tu m'attends, n'est-ce pas, comme je t'aatends, avec la même forte et longue fidélité, avec crainte et certitude.

[Every time that I leave you, I have an anguish and feel a tremor at the bottom of my heart. Where are you ? Where are you, my love ? You are waiting for me, aren't you, as I am waiting for you, with the same strong and consistent loyalty, with fear and certainty.]

At times, Tout cela est stupide et n'a aucun sens* (all is stupid and have no sense), dear master and absolute governor. To lose You, to have no access to Your grace, Your Grace, is really unfortunate and hurtful. If only You could write to me! [Vous] ne peux pas savoir le bonheur que m'apporte la chère écriture.* (You cannot know the happiness that the dear writing provides me with.)

You, mystical person of the highest qualities, are so high in the hierarchy of human beings, that I cannot say, as the writer said, "avec toutes nos différences, nous sommes si semblables, si fraternels et si complices (au beau sense du mot)"*. On the contrary, we are really different, and very distant in the cosmic order.

Even with this belief, is it possible que nou pouissons enfin nous appuyer l'un sur l'autre, vraiment ! Il me semble qu'alors il n'y aurait pas de limite à mes forces. Et, pour tout ce que je veux faire, j'ai besoin de forces sans limites (we may finally be able to lean on each other, really! It seems to me that then there would be no limit to my strength. And, for everything I want to do, I need strength with no limits.)*

After re-reading this last paragraph, I think it is applicable to me what Camus wrote, who said to his beloved*:

Tu vois, je suis un incorrigible imbécile. [You see, I am an incorrigible idiot],

:-)

My person of the ҉ incomprehensibly wonderful members, incapable of being grasped with the mind, hard even to look on ҉ ,** despite the years already passed I cannot forget Your divine voice, graceful movements, & treatment of the others.

Of course the memories fade :-( , and have no longer Your sacred words and laughter in a part of my brain from which to recall them with ease, but even so, I feel at times I am right next to that secret temple where encapsulated in gold we Your sad followers could find the vibrations of air that You uttered so much time ago. :-)

Your spiritual attributes were so magical, Your Honor, that at times it seems to me that just with a bit more effort I could recover those air waves stored in the hidden shrine and hear Your voice again, as if time didn't pass.

But what I am saying? Obviously je suis désorienté, bizarrement inapte, incapable de rien faire (I'm disoriented, unfit in an indescribable way, unable to do anything)*. In great part is my not having Your light in my life.

In other part, I am sure that endogenous reasons would make me suffer all the same, even if having everything I needed or wanted. Even if You paid attention to me, my frail nature would be the source of sufferings.

---

In the human nature department, I wanted to share with You, my lord, these newspieces... Beyond what is diffcult to know and needs lots of work (learning about our hospital surviving rates for surgery and illnesses), we focus in the easy to process, things like how warm are the nurses, or having hotel-like rooms†:

Abstract: Consumer-driven health care is often heralded as a new quality paradigm in medicine. However, patients-as-consumers face difficulties in judging the quality of their medical treatment. With a sample of 3,000 U.S. hospitals, we find that neither medical quality nor patient survival rates have much impact on patient satisfaction with their hospital. In contrast, patients are very sensitive to the “room and board” aspects of care that are highly visible. Quiet rooms have a larger impact on patient satisfaction than medical quality, and communication with nurses affects satisfaction far more than the hospital-level risk of dying. Hospitality experiences create a halo effect of patient goodwill, while medical excellence and patient safety do not. Moreover, when hospitals face greater competition from other hospitals, patient satisfaction is higher but medical quality is lower. Consumer-driven health care creates pressures for hospitals to be more like hotels. These findings lend broader insight into unintended consequences of marketization.

The second paper, summarized here, tells us that demagogues do not mobilize the unconvinced, but coordinate the already prone to resort to violence‡:

Abstract: Large-scale mobilization is often accompanied by the emergence of demagogic leaders and the circulation of unverified rumors, especially if the mobilization happens in support of violent or disruptive projects. In those circumstances, researchers and commentators frequently explain the mobilization as a result of mass manipulation. Against this view, evolutionary psychologists have provided evidence that human psychology contains mechanisms for avoiding manipulation and new studies suggest that political manipulation attempts are, in general, ineffective. Instead, we can understand decisions to follow demagogic leaders and circulate fringe rumors as attempts to solve a social problem inherent to mobilization processes: The coordination problem. Essentially, these decisions reflect attempts to align the attention of individuals already disposed for conflict.

To close this letter, friend of the beautiful, and the honest, and of what is good, I wish to show You some of what Don Denis of Portugal wrote to his lady. Just a common case of unrequited love֍:

Prazmi a mí, senhor, de morrer,                   [Pláceme a mí, senhor, morir,

e prazm’ ende por vosso mal,                       y pláceme también por vuestro mal,

ca sei que sentiredes qual                            que sé que sentiréis tal

mingua vós, pois ei de fazer,                        mengua vos (pues así lo haré),

ca non perde pouco senhor                          porque no pierde poco la senhor                                      

quando perde tal servidor                             cuando pierde tal servidor

qual perdedes en me perder.                       como el que vos perdéis al perderme.

E con mia mort’ ei eu prazer,                       Y con mi muerte tengo yo placer,                                        

porque sei que vos farei tal                           porque sé que a vos haré tal                                     

mingua qual fez omen leal,                           mengua, como la de un hombre leal,

o máis que podia seer                                  todo lo más que se puede ser

a quen ama, pois morto for,                          por quien se ama, hasta la muerte,

e fostes vós mui sabedor                              porque supisteis vos 

d’ eu por vós atal mort’ aver.                         que yo por vos tal muerte tendría.

E pero que ei de sofrer                                 Y ya que he de sufrir

a morte mui descomunal                              una muerte tan descomunal,

con mia mort’ oimais non m’ én cal,             con mi muerte desde hoy nada me importará,

por quanto vos quero dizer                           y por eso os quiero decir

ca meu serviç’ e meu amor                           que mi servicio y mi amor

seravos d’ escusar peior                               serán a vos de excusar peor

que a min d’ escusar viver.                           que a mí de excusar vivir.

E certo podedes saber                                 Y ciertamente, podéis saber

que pero s’ o meu tempo sal                        que ya que mi tiempo se acaba

per morte, non á ja i al                                  por la muerte, y ya nada importa,

que me non quer’ end’ eu doer,                    y no me quiero de ello doler,

porque a vós farei maior                               porque a vos haré mayor

mingua que fez Nostro Senhor                     mengua que la que hizo Nuestro Señor

de vassal’ a senhor prender.                        cuando a este vasallo arrancó de su senhor.]

(senhor = the lady)

Rien, rien n'a plus de sens pour moi, Your Honor... Je ne sais plus vivre.* Yours faithfully

a. r. ante Su Señoría

--

Notes

* Albert Camus & Maria Casarès's Correspondance. Paris: Gallimard, 2017. Page 109; 109; 103; 97; 96; 92; 92; 92; 89; 98.

** enūma eliš ("When Above," or "The Marduk Exaltation Poem," or "The Babylonian Creation Epic"), tablet I, adapted from the ETANA webpage, digital version at http://www.etana.org/node/581.

† Patients as Consumers in the Market for Medicine: The Halo Effect of Hospitality. Cristobal Young, Xinxiang Chen. Social Forces, soaa007, February 13 2020, https://www.bipartisanalliance.com/2020/02/quiet-rooms-have-larger-impact-on.html

‡ The Evolutionary Psychology of Mass Mobilization: How Disinformation and Demagogues Coordinate Rather Than Manipulate. Michael Bang Petersen. Current Opinion in Psychology, February 20 2020. https://www.bipartisanalliance.com/2020/02/we-got-psychological-defenses-against.html

Highlights

• Violent mobilization is often attributed to manipulation from, for example, demagogues.

• The human mind contains psychological defenses against manipulation, also in politics.

• Mass mobilization requires that the attention of group members is coordinated.

• Demagogues and disinformation can be explained as tools for achieving coordination.

• Mobilized individuals are predisposed for conflict rather than manipulated into conflict.

֍ Adapted from María Gimena del Rio Riande's Cantigas del rey Don Denis. In "Un libro oscuro. 105 poemas negros". Buenos Aires: Bajo la luna, 2012. https://www.aacademica.org/gimena.delrio.riande/135

In aged mice, the kinds of memory problems common in old age can be reversed, and all it takes is some cerebrospinal fluid harvested from the young

Young CSF restores oligodendrogenesis and memory in aged mice via Fgf17. Tal Iram et al. Nature May 11 2022. https://www.nature.com/articles/s41586-022-04722-0

Abstract: Recent understanding of how the systemic environment shapes the brain throughout life has led to numerous intervention strategies to slow brain ageing1,2,3. Cerebrospinal fluid (CSF) makes up the immediate environment of brain cells, providing them with nourishing compounds4,5. We discovered that infusing young CSF directly into aged brains improves memory function. Unbiased transcriptome analysis of the hippocampus identified oligodendrocytes to be most responsive to this rejuvenated CSF environment. We further showed that young CSF boosts oligodendrocyte progenitor cell (OPC) proliferation and differentiation in the aged hippocampus and in primary OPC cultures. Using SLAMseq to metabolically label nascent mRNA, we identified serum response factor (SRF), a transcription factor that drives actin cytoskeleton rearrangement, as a mediator of OPC proliferation following exposure to young CSF. With age, SRF expression decreases in hippocampal OPCs, and the pathway is induced by acute injection with young CSF. We screened for potential SRF activators in CSF and found that fibroblast growth factor 17 (Fgf17) infusion is sufficient to induce OPC proliferation and long-term memory consolidation in aged mice while Fgf17 blockade impairs cognition in young mice. These findings demonstrate the rejuvenating power of young CSF and identify Fgf17 as a key target to restore oligodendrocyte function in the ageing brain.

Popular version, excerpts from Old Mice 'Rejuvenated' With Injections of Brain Fluid From The Young (sciencealert.com), by Jacinta Bowler:

While immortality might forever be out of reach, a long, healthy retirement is the stuff dreams are made of.

To that end, a recent study suggests that the kinds of memory problems common in old age can be reversed, and all it takes is some cerebrospinal fluid harvested from the young. In mice, at least.

If this is sounding a little familiar, you might be thinking of a similar series of studies done back in the mid-2010s, which found that older mice could be generally 'rejuvenated' with the blood of younger animals – both from humans and from mice. The FDA even had to warn people to stop doing it.

This new study instead examined the links between memory and cerebrospinal fluid fluid (CSF), and the results show considerable promise, even providing a mechanism for how it works, and highlighting a potential growth factor that could mimic the results.

"We know that CSF composition changes with age, and, in fact, these changes are used routinely in the clinic to assess brain health and disease biomarkers," Stanford University neurologist Tal Iram told ScienceAlert.

[...]

To investigate, the researchers, led by Iram, took older mice (between 18–22 months old) and gave them light shocks on the foot, at the same time as a tone and flashing light were activated. The mice were then split into groups, and either given young mouse CSF (from animals 10 weeks old) or artificial CSF.

[graphs]

In experiments like this, if the mice 'freeze' when they see the tone and light, it means they're remembering the foot shock, and are preparing for it to happen again.

In this study, three weeks after the foot shocks were conducted (which the team called "memory acquisition"), the researchers tested the mice, finding that the animals that had been given the CSF from young mice showed higher-than-average freezing rates, suggesting they had better memory.

This was followed up by a battery of other experiments to test the theory, which revealed that certain genes (that are different in young-versus-old CSF) could be used to get the same response. In other words, without needing to extract someone's brain fluid.

"When we took a deeper look into gene changes that occurred in the hippocampus (a region associated with memory and aging-related cognitive decline), we found, to our surprise, a strong signature of genes that belong to oligodendrocytes," Iram told ScienceAlert.

"Oligodendrocytes are unique because their progenitors are still present in vast numbers in the aged brain, but they are very slow in responding to cues that promote their differentiation. We found that when they are re-exposed to young CSF, they proliferate and produce more myelin in the hippocampus."

[graphs]

In the mice, an infusion of a fibroblast growth factor called FGF17 was able to boost oligodendrocyte progenitor cells in a similar way to the CSF injection.

Oligodendrocytes are particularly helpful because they produce myelin, a material that covers and insulates neuron fibers. The infusion of FGF17 was itself able to help the older mice increase memory ability.

While this field of research has a very very long way to go before we can use such insights to increase memory in older humans, the findings are exciting [...]

Serbian Roma: Girls were the preferred sex, owing to expected fitness benefits; Roma fathers tend to bias their investment towards taller, more endowed children, because of greater fitness pay-off

Paternal investment, stepfather presence and early child development and growth among Serbian Roma. Jelena Čvorović. Evolutionary Human Sciences, Vol 4, April 18 2022. https://www.cambridge.org/core/journals/evolutionary-human-sciences/article/paternal-investment-stepfather-presence-and-early-child-development-and-growth-among-serbian-roma/F3B5185E6333B85FEF0ACCFD5685FCA4

Abstract: Research on paternal investment and child growth and development is limited outside of high-income countries. Using nationally representative data from low-resource Serbian Roma communities, this study examined father investment (direct care), its predictors and the associations between paternal investment, stepfather presence and child physical growth and early development. The sample included 1222 children aged 35–59 months, out of which 235 were living with biological fathers. Child outcomes included height-for-age Z-scores, stunting and early child developmental score. Roma paternal investment was relatively low. There was a positive association of father investment and children's height, and no association with developmental score. The presence of father vs. stepfather did not exert any influence on children. Instead, maternal and child characteristics explained both the overall development and height for Roma children. Thus, older children, born to literate, lower parity mothers of higher status and greater investment had better developmental and growth outcomes; girls were the preferred sex, owing to expected fitness benefits. Reverse causality emerged as the most likely pathway through which the cross-sectional association of father direct care with child growth may manifest, such that Roma fathers tend to bias their investment towards taller, more endowed children, because of greater fitness pay-off.

Discussion

This paper used nationally representative data from Serbian Roma communities to assess paternal investment (as defined in this paper) and its predictors, and the associations between paternal investment, stepfather presence and early child development and physical growth.

There were several main findings. In this Roma sample, parental investment in a number of direct care behaviours was relatively low, while maternal and paternal investments were positively correlated. Overall, almost 10% of children did not receive any investment from their parents, as measured in the present study. In line with other studies from low- and middle-income countries, almost one-third of Roma fathers did not interact with their children in the surveyed care behaviours, twice the proportion of unengaged Roma mothers: 29.7 vs. 14.2% (Jeong et al., Reference Jeong, McCoy, Yousafzai, Salhi and Fink2016; Sun et al., Reference Sun, Liu, Chen, Rao and Liu2016). There was a cross-sectional association between father's investment with child's height and stunting, while maternal investment and child's height appeared to be predictors of father's investment. There were no associations between father's investment and developmental score, and stepfather vs. father presence and Roma children outcomes. Instead, maternal and child characteristics explained both the overall development and height for Roma children.

Parenting practices may be influenced by a range of child and family characteristics, and political and economic development (Walker et al., Reference Walker, Wachs, Grantham-McGregor, Black, Nelson, Huffman and Richter2011). In addition, local culture and traditions influence parenting behaviour: in many countries, childcare is culturally ‘mother centric’, with low participation from fathers (Hosegood & Madhavan, Reference Hosegood and Madhavan2010). Thus, for instance, an average Serbian father spends only 11 minutes per day with his children, while only one in 20 fathers is fully involved in parenting (Republički zavod za Statistiku, 2020). The observed low paternal investment of Roma fathers may reflect the prevailing dominant patriarchal cultural pattern with a significant sex asymmetry in parenting (Čvorović & Coe, Reference Čvorović and Coe2019). Additionally, bias in maternal reporting could account for this finding – studies have found that generally fathers tend to report significantly higher levels of involvement than mothers, contingent on numerous factors including ethnicity, the quality of the couple's relationship and the child characteristics (Charles et al., Reference Charles, Spielfogel, Gorman-Smith, Schoeny, Henry and Tolan2018).

Previous research found inconsistent relationships between father's direct care and children's height (Maselko et al., Reference Maselko, Hagaman, Bates, Bhalotra, Biroli, Gallis and Rahman2019; Jeong et al., Reference Jeong, McCoy, Yousafzai, Salhi and Fink2016), but in this study, after adjusting for potential confounding factors, Roma fathers’ direct care was positively associated with their children's height. Fathers may contribute to their offspring's well-being in a number of ways: additive paternal care (‘cooperative care’ where both parents work together to care for children at the same time) can include complementing the mother's direct care or providing resources that allow for better nutrition (Gurven et al., Reference Gurven, Winking, Kaplan, von Rueden and McAllister2009). Additive care may also include playing with a child or teaching (Starkweather et al., Reference Starkweather, Keith, Prall, Alam, Zohora and Emery Thompson2021). Paternal additive direct care may have similar impact to that of other allomothers: a child may receive a better overall gain and additive investments that thus could lead to better fitness outcomes (Emmott & Page, Reference Emmott, Page, Shackelford, A and Weekes-Shackelford2019). Given the positive correlation of Roma maternal and paternal investment, the overall investment may have positively affected children, resulting in better outcomes. However, the most obvious mode that paternal direct care can influence growth is via nutrition, i.e. feeding. MICS is cross-sectional in design, and measures of direct parental involvement did not include feeding practices, thus the results may be confounded by an unmeasured variable that correlates with paternal care. In this setting, another possible pathway that may reflect on the positive association between father investment and child height is reverse causality, such that fathers provided more care to taller/healthier children (Maselko et al., Reference Maselko, Hagaman, Bates, Bhalotra, Biroli, Gallis and Rahman2019). A Roma child's height, in addition to maternal investment, predicted father's investment: taller children had fathers who provided more direct care. In young children, height serves as a proxy for the cumulative effect of nutritional and health loads from conception (Frongillio et al., Reference Frongillo, Kulkarni, Basnet and de Castro2017). Thus, early childhood growth is an important measure of offspring quality, as it may influence future health and reproduction (Kramer et al., Reference Kramer, Veile and Otárola-Castillo2016).

Additionally, Roma child's height and the chances of stunting were influenced by the child's sex: Roma boys were more likely to be shorter and stunted than Roma girls, suggesting that they were more susceptible to nutritional inequalities than their girl counterparts of the same age. This pattern is consistent with previous findings where biased paternal investment was associated with the children's health/height but also sex (Alvergne et al., Reference Alvergne, Faurie and Raymond2009; Čvorović, Reference Čvorović2020a; Hagen et al., Reference Hagen, Hames, Craig, Lauer and Price2001). Among the Roma, parents may selectively invest in and support taller children (girls) who had the greatest potential to survive into adulthood and reproduce successfully, thus making the parents into grandparents, or in other words, enhancing the parents’ reproductive success (Čvorović, Reference Čvorović2020a). Sex preferencing among the Roma in favouring girls is a common finding in Hungarian Roma groups as well (Bereczkei & Dunbar, Reference Bereczkei and Dunbar2002). Roma girls more often than boys engage in helping-at-the-nest, have a greater chance of marrying up the socio-economic scale and produce more surviving children compared with sons. In addition, having a high-quality (taller/healthier) daughter is regarded as a considerable advantage and a source of income among Serbian Roma who practice bride price (Čvorović, Reference Čvorović2014).

Compared with other studies, where socioeconomic status and parental education were positively associated with early child development (Urke et al., Reference Urke, Contreras and Matanda2018; Jeong et al., Reference Jeong, McCoy and Fink2017; Paxson & Schady, Reference Paxson and Schady2010), in this setting, there was an apparent lack of relationship between child developmental score and also four domains of development (literacy–numeracy, physical, socioemotional and learning) with paternal investment and other variables.

In contrast to other studies, when a stepfather was introduced to the context, the presence of either father or stepfather had no influence on Roma children outcomes (Case & Paxson, Reference Case and Paxson2001). Instead, child's age and maternal characteristics explained both the height and overall development for Roma children. Thus, older children were taller and had higher developmental score. Older children have higher reproductive value, and in poor populations, the later born children are often disadvantaged relative to earlier borns in nutritional status and growth, having higher morbidity and mortality (Lawson & Mace, Reference Lawson and Mace2009). In addition, maternal parity was negatively associated with child's height. Roma mothers with higher parity had children who were shorter than those of mothers with lower parity. Under poor conditions, numerous siblings may put children at higher risk of malnutrition, because of the discrepancy between family size and available resources. Maternal parity may also serve as a rough measure for investment: body size may be a proxy for a trade-off between offspring number and quality, or between the number and size of offspring, especially under resource-scarce conditions and in high-fertility settings such as with the Roma (Walker et al., Reference Walker, Gurven, Burger and Hamilton2008). Maternal parity was higher in stepfather households, but interestingly, unlike in other studies (Amato & Rivera, Reference Amato and Rivera1999; Lawson & Mace, Reference Lawson and Mace2009), maternal investment was higher for children living with stepfathers. One possible explanation as of why children living with stepfathers experience higher maternal investment may be that a stepfather is providing some extra resources, thus the mother may be experiencing a higher quality of life in this new relationship, both of which enable the mother to better provide for her children, including direct care. MICS does not include information on stepfathers’ resources, while maternal age, basic literacy skills and access to improved sanitation (as proxies for socioeconomic status) did not differ between mothers living with biological fathers vs. stepfathers. A more likely explanation is that Roma mothers in stepfather households may be compensating for the absence of a biological father by focusing more investment and attention on the children from former unions (Emmot & Mace, Reference Emmott and Mace2014). Higher investment and more attention could also serve as protection for any number of possible negative effects in the new home. This context could perhaps explain the lack of association of maternal and paternal characteristics and child development and maternal characteristics and child height: the poor conditions may have affected the ability of Roma parents to invest, and to make substantially enough investment to be detected or differentiate between children. Thus, mothers ‘get activated’ only in the presence of stepfathers (high risk), to protect their children and compensate for even the limited paternal investment. Roma children may be sensitive to this particular setting as well: child's age was associated with growth and development only in the stepfather's presence, thus younger and older sibling get to compete more in a stepfather's household, as there is an actual maternal investment to compete for.

Furthermore, maternal age was positively associated with both height and development: generally, older mothers tend to invest more in offspring, as they are less likely to have additional children and the investment focuses on the children they already have (Uggla & Mace, Reference Uggla and Mace2016). An additional explanation could be that this relationship reflects on maternal status within a family. Many Roma women face inflexible gender roles and expectations, and for many, having children in marriage is the only socially endorsed route for an improvement in status (Čvorović & Coe, Reference Čvorović and Coe2019). A higher maternal status within a Roma family may include more power in decision-making concerning child's wellbeing such as diet and activities.

Additionally, there was a positive association of child's age, maternal investment, and literacy with children's overall developmental score. As a child ages, it is more likely to develop and learn skills and be ahead in development. The importance of maternal care behaviours and education for children's early development has been well described: parental support for learning (such as stimulating interactions and reading books) was found to be an important means through which parental education is associated with children's development (Sun et al., Reference Sun, Liu, Chen, Rao and Liu2016; Jeong et al., Reference Jeong, McCoy and Fink2017; Walker et al., Reference Walker, Wachs, Grantham-McGregor, Black, Nelson, Huffman and Richter2011). In turn, maternal education can facilitate maternal investment and practices, as increasing levels of education lead to different thinking and decision-making patterns (Cutler & Lleras-Muney, Reference Cutler and Lleras-Muney2010). This may be especially important to the Roma, given the high illiteracy rate among females: even low levels of education increase children's well-being and survival prospects (Sandiford et al., Reference Sandiford, Cassel, Sanchez and Coldham1997; Čvorović, Reference Čvorović2020a).

To the best of my knowledge, this is the first study to provide an account of paternal direct care as a proxy for investment, stepfather presence and child development and growth among the low-resource Roma. The study findings contribute new evidence of the drivers or lack of it of development and growth among children in marginalised ethnic populations, adding to the literature about paternal investment and child outcomes.

The majority of Roma children grow up in poverty, born to mothers with low education, and in homes with limited learning opportunities. In this context, parental investment was relatively low. Fathers have limited involvement in direct care of their young children and this involvement was not associated with child development. The presence of a father vs. a stepfather did not exert any influence on Roma children, insomuch as it did not have direct influence on the children's’ outcomes of growth and development. Roma paternal investment was low to begin with and father absence is likely to be less important in settings where fathers usually provide less support for their children (Lawson et al., Reference Lawson, Schaffnit, Hassan, Ngadaya, Ngowi, Mfinanga and Borgerhoff Mulder2017). In the presence of a stepfather, maternal and child's traits explained overall child development and growth. Maternal investment was higher for children living with stepfathers, thus mothers may be protecting their children from previous unions and compensating for paternal absence. Competition among Roma children – among younger and older siblings – was evident only when maternal investment was significant, in the presence of a stepfather. Thus, older children, born to literate, lower parity mothers of higher status and greater investment had better developmental and growth outcomes; girls were the preferred sex, as they were likely to be taller and less stunted than Roma boys, possibly owing to expected fitness benefits. Reverse causality emerged as the most likely pathway through which the cross-sectional, positive association of father direct care with child growth may manifest, such that Roma fathers tend to bias their investment towards taller, more endowed children, because of greater fitness pay-off.

The study had several limitations. The data were cross-sectional, limiting causal inferences between the variables under study. The developmental score and paternal investment were mother-reported and thus subject to biases: both measure how mothers perceived their child's development and their husbands’ involvement, and not actual child development and paternal behaviour. Furthermore, the reliability of Early Child Development scale was fair but similar to other recent studies, reflecting its limited adaptation to local culture and context (Urke et al., Reference Urke, Contreras and Matanda2018; McCoy et al., Reference McCoy, Sudfeld, Bellinger, Muhihi, Ashery, Weary and Fink2017). The questions regarding literacy/numeracy have been shown to be too advanced for 3- and 4-year-old children (McCoy et al., Reference McCoy, Peet, Ezzati, Danaei, Black, Sudfeld and Fink2016), this being particularly pertinent as regards Roma and other disadvantaged children where parental literacy is limited.

Additionally, to date, no specific growth references have been developed for the Roma, even though their Indian origin indicate an ethnicity impact to the anthropometric measures. Albeit the population-specific growth references may serve as a more biologically relevant measure of within-population assessment of children's growth (Kramer et al., Reference Kramer, Veile and Otárola-Castillo2016; Martin et al., Reference Martin, Blackwell, Kaplan and Gurven2019), the effects found in this study may be considerable, ranging from an approximately 0.33 SD in child's height to a more than 1 SD difference in paternal care (Winking & Koster Reference Winking and Koster2015).

As child's growth and development are sensitive to available resources, and may be affected by aspects outside of direct family influence (Lawson et al., Reference Lawson, Schaffnit, Hassan, Ngadaya, Ngowi, Mfinanga and Borgerhoff Mulder2017; Winking & Koster, Reference Winking and Koster2015), social assistance (cash transfers) may also have an effect on Roma family, including the growth and development of Roma children. For instance, in affluent settings, fathers tend to engage more in direct child care if their wives are employed and/or contribute a greater share of the couple's earnings (Raley et al., Reference Raley, Bianchi and Wang2012). Roma mothers’ receipt of welfare could motivate Roma fathers to engage in direct child care: the majority of Roma women do not work (formal income leads to withdrawal of social benefits), but still support the family with cash transfers. Nevertheless, a recent study found that among Serbian Roma, receiving social assistance was associated with disintegration and a diminished role of the family (Čvorović & Vojinović, Reference Čvorović and Vojinović2020), but whether welfare influence father–child relationships and child outcomes remains unexplored. Also, other potential confounders, such as parental height and health status, were not collected. To fully understand the effects of paternal investment on child outcomes, information should be collected directly from fathers and father-like figures and/or through observation, and include parental anthropometrics, as well as data on the presence of alloparents, which may have an effect on child outcomes, including growth (Sear & Mace, Reference Sear and Mace2008).

Low-intensity pleasure (familiar calm activities such as playing peek-a-boo) was the most influential variable in distinguishing boys from girls; girls came out higher on fear, falling reactivity, and low intensity pleasure, & boys higher on approach

Citation: Gartstein MA, Seamon DE, Mattera JA, Bosquet Enlow M, Wright RJ, Perez-Edgar K, et al. (2022) Using machine learning to understand age and gender classification based on infant temperament. PLoS ONE 17(4): e0266026. https://doi.org/10.1371/journal.pone.0266026

Abstract: Age and gender differences are prominent in the temperament literature, with the former particularly salient in infancy and the latter noted as early as the first year of life. This study represents a meta-analysis utilizing Infant Behavior Questionnaire-Revised (IBQ-R) data collected across multiple laboratories (N = 4438) to overcome limitations of smaller samples in elucidating links among temperament, age, and gender in early childhood. Algorithmic modeling techniques were leveraged to discern the extent to which the 14 IBQ-R subscale scores accurately classified participating children as boys (n = 2,298) and girls (n = 2,093), and into three age groups: youngest (< 24 weeks; n = 1,102), mid-range (24 to 48 weeks; n = 2,557), and oldest (> 48 weeks; n = 779). Additionally, simultaneous classification into age and gender categories was performed, providing an opportunity to consider the extent to which gender differences in temperament are informed by infant age. Results indicated that overall age group classification was more accurate than child gender models, suggesting that age-related changes are more salient than gender differences in early childhood with respect to temperament attributes. However, gender-based classification was superior in the oldest age group, suggesting temperament differences between boys and girls are accentuated with development. Fear emerged as the subscale contributing to accurate classifications most notably overall. This study leads infancy research and meta-analytic investigations more broadly in a new direction as a methodological demonstration, and also provides most optimal comparative data for the IBQ-R based on the largest and most representative dataset to date.

Discussion

We set out to leverage existing IBQ-R datasets from multiple laboratories (N = 4,438) to address an important gap in research by investigating age and gender classifications in early childhood, and overcoming limitations of the published studies such as small sample sizes that cannot be considered representative or provide widely generalizable results. Relying on algorithmic modeling techniques, 14 IBQ-R subscale scores served as features used to classify participating children as boys (n = 2,298) and girls (n = 2,093), and into three age groups: youngest (< 24 weeks; n = 1,102), mid-range (24 to 48 weeks; n = 2,557), and oldest (> 48 weeks; n = 779). Importantly, this approach allowed us to simultaneously classify infants into age and gender categories, providing an opportunity for the first time to consider the extent to which gender differences are informed by infant age. This study also makes an important contribution to the literature as a novel methodological demonstration. That is, the present application of machine learning algorithms provides a new direction for infancy and temperament research, as well as meta-analytic investigations more broadly.

Results based on accuracy indicators (the inverse of misclassification rates), Cohen’s kappa coefficients, and AUC (incorporating sensitivity and specificity parameters) demonstrated that temperament features provided superior classification of age groups relative to gender, which is consistent with the existing literature insofar as age effects have generally been more robust (e.g., not dependent on methodology; [5,26,52]). As noted, gender differences in infancy have been largely limited to activity level and fear/behavioral inhibition, with higher activity level and approach reported for boys [29,30] and greater fear/behavioral inhibition for girls [14,25,31,35,36]. These gender differences are somewhat controversial due to a lack of consensus regarding their origin (i.e., biologically based or largely a function of socialization; [53]) and questions regarding the role of parental expectations. That is, parents could rate boys and girls differently not due to actual variability in behavior but as a function of their own culturally influenced ideas about what is typical behavior in boys vs. girls. This explanation cannot be ruled out completely, although existing research suggests that gender differences are not entirely dependent on methodology (i.e., have been identified via behavioral observations along with parent report; [33,52]).

Importantly, gender classification by age groups results suggest this is most effective for the oldest age group, in line with the literature that indicates gender differences in temperament attributes become more pronounced with age [54]. Although a number of factors could be contributing to this pattern of results—accentuated gender differences in temperament with increasing age, and, conversely more accurate classification of gender with temperament features for oldest participants—socialization is often described as critical among these. The primary mechanism invoked in such explanations involves the infants’ interactional history, and is consistent with literature that indicates mothers respond differently to their sons and daughters [55–59], presenting with different affordances as social interaction partners (e.g., [60]). Over time, such differences could result in divergent trajectories with respect to temperament due to differences in socialization goals/approaches for boys vs. girls. Specifically, parents may prioritize relationship orientation for daughters, but competence and autonomy for sons [61–63]. These and other socialization-related pathways may be responsible for the stronger temperament-based classification of boys and girls later in infancy observed herein.

At the same time, gender is viewed as a marker for a host of sex-linked distinctions in physiological processes. For example, prenatal exposure to high levels of androgen is predictive of later behavior problems, primarily of the externalizing type (e.g., ADHD; [64]), and used to explain early vulnerability observed in boys with respect to this set of problems [65]. Postpartum biological effects are also possible, for example via testosterone increases for boys in infancy, referred to as “mini-puberty,” peaking by the second month and returning to baseline at about 6 months [66]. Sex-linked differentiation in brain structures and functions occurs with maturation, resulting in greater discrepancies with age. For example, Goldstein et al. [67] reported that the amygdala tends to be larger in males and the hippocampus larger in females (see Hines [68] for a related review).

Follow-up analyses outlining feature importance for classification models were performed for the Ensembled Decision Trees (Random Forest) to further interpretation of the observed results. Random Forest methods provide an effective mechanism for feature selection and importance using tree-based mechanisms to rank node classification via the mean decrease in gini impurity, i.e., the probability that a random sample in a particular tree node would be mislabeled using the distribution of the node sample, averaged across all trees [69]. Figures provided in Supplemental Materials (S1–S3 Figs) demonstrate that while Fear was the most important feature in distinguishing boys and girls for the youngest and mid-range age group, for oldest infants, low intensity pleasure was most influential. In fact, for youngest infants (S3 Fig), all three distress-related scales (Fear, Distress to Limitations, Sadness) were of primary importance in classifying infants accurately by gender via the Random Forest algorithm. Positive emotionality and regulatory dimensions of temperament (e.g., Falling Reactivity, Approach) begin to take on greater importance for mid-range and oldest infants. Notably, certain temperament features detracted from model accuracy in classifying infants by gender (i.e., associated with lowest negative importance values), particularly Cuddliness, Vocal Reactivity, and Smiling and Laughter in the youngest age group and Smiling and Laughter, Perceptual Sensitivity, and Activity in the oldest age group. These results identify the temperament attributes that did not differentiate boys and girls effectively, and it is of interest that the list of these poorly differentiating features varied by age. When the most important features were considered for age classification and gender classification models only, Fear again emerged as the critical dimension, which is in line with the extensive literature documenting the developmental progression as well as gender differences for this domain of temperament [2,13,14,26,54].

This work is not without limitations, chief among these our reliance on a single method (i.e., parent report) in the assessment of infant temperament. Future studies should aggregate datasets providing different sources of information, including behavioral observations and physiological measures, such as cortisol reactivity, heart rate variability/respiratory sinus arrhythmia, and/or frontal alpha asymmetry ascertained via electroencephalogram (EEG) recordings. In addition, the outcomes examined in this study were limited to child gender and age. Future studies with older children should conduct classification analyses with additional dependent variables, particularly symptom and disorder classifications (e.g., clinical/subclinical/asymptomatic ADHD). It should be noted that we did not consider classification based on race/ethnicity because of a far more limited literature suggesting these differences can be discerned on the basis of temperament, and future research should examine related models, as relevant studies accumulate. Finally, the present modeling approach could be extended and potentially improved by applying ensembling modeling approaches (i.e., using multiple algorithms simultaneously), as opposed to relying on singular modeling frameworks.

This study underscores the importance of meta-analytic investigations and cross-laboratory collaborations, providing illusive answers to questions, such as those related to intersections of gender and age in temperament development, that have not been previously addressed. Because of the large cross-laboratory sample included herein, this study provides most optimal comparative data for the IBQ-R (Table 2), which has emerged as a widely used infant temperament assessment tool. Importantly, the present investigation serves as a methodological illustration for application of machine learning techniques in infancy and temperament research, as well as developmental science more broadly. Given the propensity for differing algorithmic methods to have strengths and weaknesses that may bias predictive outcomes and classification accuracy, we selected 11 established algorithmic modeling and classification techniques to quantify the most robust outcomes, simultaneously demonstrating the viability of machine learning approaches in this area of scientific inquiry. Results of this study make an important contribution to developmental temperament research, demonstrating effective age group classification on the basis of fine-grained temperament features, and indicating more effective gender classification for the older age group, with multiple implications for future mechanistic research examining potential socialization and biological contributors.