Unambiguous chickens were not present until ∼1650 to 1250 BCE in central Thailand; production and storage of rice & millet may have acted as a magnet, thus initiating the chicken domestication process

The biocultural origins and dispersal of domestic chickens. Joris Peters et al. Proceedings of the National Academy of Sciences, 119 (24) e2121978119, June 6, 2022. https://doi.org/10.1073/pnas.2121978119

Significance: Chickens are the world’s most numerous domestic animal. In order to understand when, where, and how they first became associated with human societies, we critically assessed the domestic status of chicken remains described in >600 sites in 89 countries, and evaluated zoogeographic, morphological, osteometric, stratigraphic, contextual, iconographic, and textual data. Although previous studies have made claims for an early origin of chickens, our results suggest that unambiguous chickens were not present until ∼1650 to 1250 BCE in central Thailand. A correlation between early chickens and the first appearance of rice and millet cultivation suggests that the production and storage of these cereals may have acted as a magnet, thus initiating the chicken domestication process.

Abstract: Though chickens are the most numerous and ubiquitous domestic bird, their origins, the circumstances of their initial association with people, and the routes along which they dispersed across the world remain controversial. In order to establish a robust spatial and temporal framework for their origins and dispersal, we assessed archaeological occurrences and the domestic status of chickens from ∼600 sites in 89 countries by combining zoogeographic, morphological, osteometric, stratigraphic, contextual, iconographic, and textual data. Our results suggest that the first unambiguous domestic chicken bones are found at Neolithic Ban Non Wat in central Thailand dated to ∼1650 to 1250 BCE, and that chickens were not domesticated in the Indian Subcontinent. Chickens did not arrive in Central China, South Asia, or Mesopotamia until the late second millennium BCE, and in Ethiopia and Mediterranean Europe by ∼800 BCE. To investigate the circumstances of their initial domestication, we correlated the temporal spread of rice and millet cultivation with the first appearance of chickens within the range of red junglefowl species. Our results suggest that agricultural practices focused on the production and storage of cereal staples served to draw arboreal red junglefowl into the human niche. Thus, the arrival of rice agriculture may have first facilitated the initiation of the chicken domestication process, and then, following their integration within human communities, allowed for their dispersal across the globe.

Discussion

Assessing the Spatiotemporal Pattern of Chicken Domestication.

Two initial hypotheses proposed separate temporal and geographic origins of domestic chickens. Zeuner (5) argued that domestic chickens were present in the Indus Valley during the mature Harappan period (∼2600 to 1900 BCE) and subsequently introduced to Mesopotamia. Based upon the presumption that archaeological bird remains dated to the sixth millennium BCE in Neolithic northern China were chickens, West and Zhou (6) claimed that chicken domestication must have taken place in Southeast Asia prior to this before being translocated into China, and then farther west following a northern route. A more recent study concluded that red junglefowl were domesticated in the Yellow River basin shortly after the onset of the Holocene (8) (SI Appendix, Table S1).

With respect to South Asia, the claim that chickens were present within the Indus Valley Civilization was based upon two bone remains from Harappa (25) and four from Mohenjo-daro (24), as well as an incomplete “hen” figurine from Mohenjo-daro (23, 79). Our reanalysis of the two Harappan bones shows that one is morphologically inconsistent with Gallus, and the other’s taxonomic classification is ambiguous. The taxonomic classification of three of the four fragmentary bird bones from Mohenjo-daro is also questionable. In addition, all of these bones, including a completely preserved femur, pertain to individuals that significantly exceed the size of prehistoric chickens. Finally, all four specimens have been collected in upper strata. Given the propensity for chicken bones to move between stratigraphic boundaries (13), it’s possible these remains are recent intrusions. These lines of evidence call into question the assumption that poultry farming was present in Bronze Age Mohenjo-daro (SI Appendix, Table S3).

Excavations conducted in other Indus Valley Civilization sites and contemporaneous settlements produced additional chicken bones, especially in Saraushtra (SI Appendix, Fig. S2). These specimens were classified as domestic fowl based on the absence of modern wild jungle fowl populations in the region (22) and the aforementioned incorrect claim for fowl husbandry in the Indus Valley. Although currently located beyond the present-day natural distribution of both red and gray junglefowl (Fig. 1 and SI Appendix, Fig. S1), this region shares similar ecological characteristics and borders the region where gray junglefowl is extant (80). It is therefore likely that the natural range of gray junglefowl extended into the Indus River basin during the Mid-Holocene, and that these remains derive instead from local wild populations. This conclusion is supported by the presence of other fauna present in zooarchaeological assemblages, or in Harappan art (including Indian Hog Deer: Axis porcinus; Swamp Deer: Cervus duvauceli; and the Indian Rhinoceros: Rhinoceros unicornis), indicating relatively larger distributions of several fauna in the past (81). The combined weight of this evidence suggests that, contrary to the long-standing hypothesis, chickens were not domesticated in the Indus Valley.

Regarding northern China, subsequent reevaluations of the galliform remains (1, 9), as well as photographs and drawings, demonstrate that they are pheasant bones (2, 82). In addition, high-resolution climate and precipitation records from temperate Holocene East Asia, and the habitat requirements of the vertebrate taxa associated with the pheasants, suggest that the subtropical forest habitat conducive to thermophilic red junglefowl did not extend into northern China during the Holocene climatic optimum (1). Finally, mitochondrial analyses of modern breeds support a late dispersal scenario of chickens into northern China (83). Our analysis thus supports a much later arrival in this region consistent with the first appearance of chickens in Japan in the early first millennium CE, and in Mongolia during the early second millennium CE.

Our combined reanalyses of zooarchaeological, linguistic, genetic, and iconographic evidence suggests the following scenario. The first chickens were likely derived from a population of the subspecies G. gallus spadiceus, whose current range spans southwestern China, northern Thailand, and Myanmar (16) (Fig.1). The first unambiguous chicken bones in the archaeological record are present within the faunal assemblage at Neolithic Ban Non Wat in central Thailand, and date to ∼1650 to 1250 BCE. Once incorporated into human societies, chickens dispersed into and beyond the range of other Gallus subspecies and species. The evidence presented here demonstrates that chickens did not appear in archaeological contexts within Central China, South Asia, or Mesopotamia until the late second millennium BCE, just before their initial presence in Melanesia. By ∼700 BCE, chickens had arrived in Ethiopia and Mediterranean Europe (Fig. 2). This western dispersal was substantially more rapid than the establishment of chicken populations in temperate regions present in higher latitudes (Fig. 2). Overall, our analyses indicate a temporal origin and spread of chickens that substantially postdates many of those suggested by previous studies (6, 8).

A Hypothesis for the Process of Chicken Domestication.

Within the native range of red junglefowl, many Southeast Asian languages refer to chickens as “bamboo fowl,” given how readily they take advantage of cyclical bamboo mass flowering and seeding events (10). Red junglefowl are also known to consume rice grains (Oryza sp.) (44, 84), a staple dietary component of Southeast Asian domestic chickens (85). Rice and millet (Setaria italica) were cultivated by mixed foraging and cereal producing Neolithic communities in mainland Southeast Asia (86–88). An analysis of the material culture (including pottery decoration) associated with these agriculturalists suggests that rice and millet cultivating communities dispersed from the Yangtze valley (89–92) into southern China, where they arrived by the mid-third millennium BCE (90, 93). From there, they continued into peninsular Southeast Asia, where people following distinct dispersal pathways emphasized either rice or millet (94).

Land reclamation for cereal cultivation led to the replacement of primary forest by secondary vegetation, a habitat more suitable for red junglefowl. Outside of bamboo thickets, red junglefowl are known to thrive in slash-and-burn agricultural systems (10). The novel presence of cultivated fields, fallow fields (necessary for either millet or rainfed rice), cereal harvest residues, remainders of human food preparation and consumption, invertebrates associated with keeping pigs and cattle, and other aspects of the human niche may have attracted red junglefowl to human settlements and their immediate catchment.

The long-term abundance of cereals within the human niche would have led to dramatic shifts in selective pressure that lasted multiple generations, including a relaxation of selection against larger clutch size, as well as increased selection against territoriality in cocks (10). These conditions likely also facilitated larger bird population densities near farming communities, followed by subsequent “accommodation” of birds within the village. The availability of cultivated cereals may have therefore catalyzed a shift in the relationship between people and red junglefowl consistent with the commensal pathway (95, 96).

The current archaeobotanical evidence indicates that sites with rice cultivation appeared within the distribution of G. gallus spadiceus [the subspecies recently identified as the most likely progenitor of chickens (16)] from about 2000 BCE in two regions: southern Yunnan and northeast Thailand (Fig. 3 and SI Appendix, Table S4). Although cereal farming was also present at this time within the inferred distributions of Gallus gallus jabouillei and G. gallus gallus, there is as yet no evidence for the early presence of domestic chicken populations. Although there is confirmation of early rice farming near coastal areas and in low-lying wetlands (86, 94), the zooarchaeological records in Neolithic Vietnam, for example, show evidence for the hunting of wetland birds, but lack remains of Gallus (97). In more interior zones, early rainfed rice/millet cultivation likely spurred a tighter relationship between people and G. gallus spadiceus, as attested by the earliest confirmed chicken bones at Ban Non Wat and Non Nok Tha (SI Appendix, Table S2) (98). Because the rice was rainfed, it would have required more land area and fallow cycles relative to later, more productive irrigated rice (87), and these conditions would have created large areas of secondary thicket vegetation. In the northern region of the G. gallus spadiceus distribution, similar processes were likely possible, but detailed avifaunal studies at prehistoric archaeological sites in Yunnan have not yet been carried out.

Fig. 3.

A map depicting the distribution of dated archaeological rice finds taken from the revised Rice Archaeological Database compiled by D.Q.F. and colleagues, RAD 2.0 (90), with newly added archaeological records and cleaned reports with associated dates that appear too early based on current understanding of archaeological chronology. This is especially the case in mainland Southeast Asia where most of the arrival of cereal agriculture is now thought to be ∼2500 BC for northern Vietnam and southernmost China only and ∼2000 BC for the rest of the region (94, 123).

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In regions north of Yunnan, wet rice agriculture, characterized by small-scale, intensive wetland fields in the Yangtze (87, 99), is present as early as 4000 to 3000 BCE, and these wet paddyfield systems spread throughout central China during the Neolithic. Chickens, however, were absent in the Neolithic (100) and only appear ∼1000 BCE (Fig. 3). Relative to wet rice, dry rice and millet cultivation that predominate in the tropical south is characterized by more extensive mosaics of field and fallow, a niche more suited to wild and commensal red junglefowl.

A Combined Chicken–Rice Dispersal Across Asia and Africa.

Following the integration of chickens and human agricultural societies, the correlated spatiotemporal patterns of rice and chicken dispersal across Asia is striking. In South Asia for example, sedentism became widespread in the Ganges plains in the second millennium BCE (22, 101), and domesticated rice, wheat, barley, and other grain crops began to dominate the economy (102, 103). At this time, agriculture in the Deccan focused on small millets, beans, and occasionally wheat and barley (22, 101). It is during this period, perhaps from the later second millennium BCE, that the subsistence context would have been ideal for chickens or commensal jungle fowl, and this timing corresponds with the arrival of bird remains unambiguously identified as chickens in the Indian subcontinent.

While there is evidence for proto-indica rice management by hunter–fisher–gatherers in the middle Ganges plains predating ∼2000 BCE (102, 104, 105), proto-indica rice was managed in natural, seasonal wetlands that were unlikely to attract Gallus in large numbers. This is illustrated by a dearth of Gallus remains and a low level of both cereal production and livestock husbandry in the archaeological record (22). The domesticated indica rice introduced ∼1600 to 1500 BCE in the Upper and Middle Ganges (104, 105) was typically rainfed in more extensive systems with periods of fallow (102, 106), and thus more attractive to fowl. Recent genomic evidence derived from modern populations suggested that although modern domestic chickens in South Asia possess signatures associated with the local subspecies G. gallus murghi, these ancestral affinities are the result not of a local, independent domestication process, but the result of admixture with introduced domestic chickens derived from G. gallus spadiceus (16).

In Iron Age Mesopotamia, rice and millet cultivation may also have been linked to the initiation and intensification of poultry farming. For example, the cultivation of Chinese millets (Panicum miliaceum, Setaria italica) began in the later second millennium BCE (107–109) and intensified after ∼1000 BCE (110, 111), precisely when poultry husbandry becomes visible archaeologically (Fig. 2 and SI Appendix, Table S2). Middle Assyrian texts also confirm that irrigated rice became established in Syria by ∼1100 BCE, and references to this practice increased from the eighth century BCE (112). Thus, alongside the diversification of grain crops, chickens may represent an additional element of the broadening of Near Eastern subsistence practices after the late Bronze Age collapse (45).

There is also a correlation in Africa between the appearance of chickens and rice agriculture. The translocation of chickens to coastal Southeast Africa and the Indian Ocean islands in the eighth/ninth centuries CE coincides with the introduction of Asian crops, such as rice, tree cotton, and mung bean (113). In addition, archaeobotanical evidence in the Niger Basin illustrates the prominent role of cereal diversification, including more widespread rice cultivation and increasing urbanism ∼300 to 900 CE (114), a temporal window that coincides with the first appearance of chickens.

Replicated in the Chinese context: Ethical reflection (college professors) generally has no positive effect on moral behavior

The moral behavior of ethics professors: A replication-extension in Chinese mainland. Tiantian Hou, Xiaojun Ding & Feng Yu. Philosophical Psychology, Jun 5 2022. https://doi.org/10.1080/09515089.2022.2084057

Abstract: The relationship between professional ethical reflection and corresponding moral behavior is an important theme of moral psychology in recent years. Following Schönegger and Wagner’s research in German-speaking countries, through a replication-extension of the original US-based research carried out by Schwitzgebel and Rust, we aim at examining their results in the Chinese context. The previous researchers have shown that ethical reflection generally has no positive effect on moral behavior. A cross validation of this result was conducted in Chinese mainland, and three issues concerning Confucian virtues were added. Through reaching out to 4482 professors and collecting 368 responses altogether, we attempted to explore whether professional ethical reflection can influence normative attitude and the moral attitude-behavior consistency. Unfortunately, the results failed to show a statistically significant difference between ethicists and other professors on most of the moral issues, with the exception of paying academic membership fees and vegetarianism, wherein ethicists do express more stringent normative attitudes, and their moral attitude and self-reported behavior are statistically consistent. Notably, Chinese professors mainly expressed morally neutral attitudes toward the issue of eating meat, and they tended to believe that ethical reflection contributes to more and better moral behaviors.

Keywords: Moral psychologyethical reflectionnormative attitudemoral behaviorattitude-behavior consistencyvegetarianism

Habitual well-digging in a rainforest-living group of East African chimpanzees, which may have been imported into the community’s behavioural repertoire by an immigrant female

Well-digging in a community of forest-living wild East African chimpanzees (Pan troglodytes schweinfurthii). Hella Péter, Klaus Zuberbühler & Catherine Hobaiter. Primates, Jun 6 2022. https://rd.springer.com/article/10.1007/s10329-022-00992-4

Abstract: Access to resources shapes species’ physiology and behaviour. Water is not typically considered a limiting resource for rainforest-living chimpanzees; however, several savannah and savannah-woodland communities show behavioural adaptations to limited water. Here, we provide a first report of habitual well-digging in a rainforest-living group of East African chimpanzees (Pan troglodytes schweinfurthii) and suggest that it may have been imported into the community’s behavioural repertoire by an immigrant female. We describe the presence and frequency of well-digging and related behaviour, and suggest that its subsequent spread in the group may have involved some degree of social learning. We highlight that subsurface water is a concealed resource, and that the limited spread of well-digging in the group may highlight the cognitive, rather than physical, challenges it presents in a rainforest environment.

Discussion

Chimpanzees living in water-restricted areas are able to exploit subsurface water by digging wells to access it (Nishida et al. 1999; McGrew et al. 2003; Hunt and McGrew 2002). Waibira chimpanzees were observed digging wells by hand next to a pool with stagnant surface water, their main water source during the dry season. We did not observe any use of tools for well-digging. Over a period of 377 days across seven annual dry seasons we documented habitual well-digging in four female chimpanzees. Importantly, this happened while stagnant surface water was available at the same time, suggesting they preferred the well water. Other individuals subsequently exploited the pre-dug wells for their own water access, either directly or by using sponges, again while (stagnant) surface water was available nearby.

Although digging behaviour (e.g. play digging) had been observed in the Waibira community prior to ONY’s immigration in 2015, we recorded no observations of well-digging in the community prior to 2015, despite camera trap video recording at the site (ongoing since January 2013) and direct observations during focal follows (ongoing since 2012). We also recorded no indirect evidence of well-digging at the water hole prior to 2015. While it is impossible to rule out that we missed this behaviour or failed to recognise the indirect traces of it, we consider it likely that ONY introduced the behaviour into the Waibira group. First, her competence and frequency of well-digging were remarkable from the beginning, suggesting that she knew the behaviour prior to immigration. Second, and equally remarkable, were the behavioural responses of other adult individuals who closely observed her well-digging behaviour and then exploited her wells over several years, suggesting that the behaviour was previously unknown to other Waibira adults.

A similar pattern was recorded in adult chimpanzees in Bossou, who closely observed (‘peering’) previously unknown nut-cracking behaviour in a field experiment (Biro et al. 2003). It has been argued that peering is a good indicator of ongoing social learning in apes (Schuppli et al. 2016), which is in line with our observations. Since its introduction in 2015, well-digging has now been observed repeatedly and in multiple individuals, suggesting it has spread–potentially by social learning–within the Waibira community. No similar behaviour has ever been observed in the well-studied neighbouring Sonso community (Reynolds 2005), despite three decades of careful observations and the fact that both groups occupy the same continuous forest habitat. Sonso chimpanzees, however, benefit from year-round access to a small river (the Sonso river), which flows across core areas of their territory and provides continuous access to fresh water.

Over the seven-season study period, we observed eight individuals to dig wells, but all four of the habitual well-diggers were females (three adults and one juvenile). While some younger males were observed to dig a well on at least one occasion, no adult male has so far been seen to dig one (although they were observed exploiting wells dug by others, suggesting a preference for the well water over the stagnant water that was still freely available). This female-biased pattern of spread is similar to that observed in Japanese macaques (Macaca fuscata) for potato washing (Nakamichi et al. 1998). Our camera trap coverage of the water hole is incomplete and it was not possible to observe all drinking events or social behaviours. Thus, it is likely that some well-digging and other digging-related behaviour were not captured in our video dataset. However, there is characteristic physical evidence of well-digging that is relatively easy to identify, such as the hole having clearly defined sides; the presence of separate marks made by fingers at the hole’s lip (where the fingers are initially dug into the soil) or in the area where the tailings remain; the presence of a small pile of substrate where the direction of digging with the fingers is consistent; in addition, the likelihood that well-digging has occurred is further supported by the presence of drinking tools in or around the hole (Video S4) (McGrew et al. 2007, 2013). During the same period of observation, the water hole and the surrounding area was surveyed regularly (at least once a week) for another study, and no indirect physical evidence of well-digging was observed prior to 2015. The failure to acquire this–very easily performed–behaviour by more individuals is puzzling, particularly since they have been observed to exploit the wells dug by other individuals. One possible explanation is that, while the physical act of well-digging for subsurface water is easy, the cognitive puzzle presented by its status as a concealed resource is more challenging, particularly given the (short) delay between the action of digging and the appearance of clean water, and the likely absence of clear cues to its presence. For example, in a muddy rainforest water hole olfactory cues to subsurface water presence are likely obscured by those from stagnant surface water. Delayed rewards or trace conditioning is shown to negatively impact the speed of learning compared to direct stimulus association (Kamin 1961; Beylin et al. 2001), and due to its significant cognitive demands, has been proposed as a possible test for animal consciousness (Shea and Heyes 2010). Additional reinforcing factors, such as observing a conspecific well-digging, may facilitate recognition of the connection between the action of manual digging and acquiring clean subsurface water.

Given wider trends in the spread and maintenance of group-specific behaviour in chimpanzees, we predict that in the future we will see (1) further spread of well-digging between adult females and immature individuals of both sexes; (2) matrilineal spread, as three of the habitual well-diggers were mature females, two of them with offspring; and (3) the possible spread to adult males with the maturation and rise in rank of immature male well-diggers.

In conclusion, we describe a new case of well-digging in chimpanzees–the first described for a rainforest-living group. We describe the apparent spread of this behaviour, which was potentially introduced by an immigrant female. The repeated innovation of well-digging across four communities of chimpanzees (McGrew et al. 2003, 2007; Hunt and McGrew 2002) could be explained by individual learning in response to a strong ecological necessity; however, the apparent absence of this behaviour in Waibira prior to ONY’s immigration, followed by its subsequent rapid acquisition by a few–but not many–group members, suggests that there was a socially mediated component to its spread in Waibira. Our observations support previous evidence suggesting that social transmission typically occurs to other younger or low or similarly ranked individuals (Horner et al. 2010). The now habitual use of a technique previously associated with communities that live in savannah or savannah-woodland highlights the importance of seasonal variation as well as broad ecological variation in resource availability for forest-dwelling chimpanzees (Wessling et al. 2018). Irrespective of the typical availability of water as a resource, the limited presence of water during at least some periods of the year appears sufficient to shape chimpanzee behaviour in the Waibira community. Taken together, these observations highlight both the striking variation and flexibility of chimpanzee behavioural repertoires.

We show that firms with more Machiavellian CEOs will have lower costs than other firms in the market, one reason why a personal characteristic that is usually seen as problematic for organizations is rather common in their upper ranks

Bargaining your way to success: The effect of Machiavellian chief executive officers on firm costs. Tessa Recendes, Federico Aime, Aaron D. Hill, Oleg V. Petrenko. Strategic Management Journal, March 27 2022. https://doi.org/10.1002/smj.3402

Research Summary: This study builds on insights from the upper echelons tradition in strategy to examine the effects of chief executive officer (CEO) Machiavellianism on relevant firm costs. While Machiavellianism has been usually construed as a purely negative trait, we argue that the pragmatic focus on the outcomes of exchanges and psychological obsession with winning in transactions that Machiavellian CEOs infuse in their organizations can have important effects on firm cost, a fundamental but frequently understudied driver of financial performance in strategic management research. In line with our arguments, we find that CEO Machiavellianism has negative effects on production costs, financing costs, and acquisition premiums. We find support for our ideas with a sample of S&P 500 CEOs, operationalizing CEO Machiavellianism using a videometric approach.

Managerial Summary: In this study, we investigate the effect of CEO Machiavellianism on firms’ costs. We show that firms with more Machiavellian CEOs will have lower costs than other firms in the market. Rather counterintuitively, this study suggests an explanation for why a personal characteristic that is usually seen as problematic for organizations is rather common in their upper ranks. Ultimately, the study demonstrates the value of the bargaining attitude that Machiavellian CEOs bring to their organizations and suggests this value should be weighed against their risks or acknowledged to manage the risks this common personal characteristic implies.

Spain & Portugal: Across a wide array of attitudes towards COVID-19, women were more likely to hold stronger, wider, and more cautionary attitudes about the virus

Opinions and options about COVID-19: Personality correlates and sex differences in two European countries. Sónia Brito-Costa, Peter Karl Jonason, Michele Tosi, Rui Antunes, Sofia Silva, Florêncio Castro. PLoS One, June 3, 2022. https://doi.org/10.1371/journal.pone.0268193

Abstract: In the initial months of the COVID-19 pandemic in 2020, we collected data (N = 1,420) from Portugal and Spain in relation to personality (i.e., Dark Triad traits, Big Five traits, religiousness, and negative affect) and attitudes related to COVID-19 about its origins, opinions on how to deal with it, and fear of it. The most pervasive patterns we found were: (1) neurotic-type dispositions were associated with stronger opinions about the origins of the virus and leave people to have more fear of the virus but also more trust in tested establishments to provide help. (2): religious people were less trusting of science, thought prayer was answer, and attributed the existence of the virus to an act of God. We also found that sex differences and country differences in attitudes towards COVID-19 were mediate by sex/country differences in personality traits like emotional stability, religiousness, and negative affect. For instance, women reported more fear of COVID-19 than men did, and this was verified by women’s greater tendency to have negative affect and low emotional stability relative to men. Results point to the central role of neuroticism in accounting for variance in broad-spectrum attitudes towards COVID-19.

Can Basic Education be Standardized? Evidence from Kenya

Gray-Lobe, Guthrie and Keats, Anthony and Kremer, Michael and Mbiti, Isaac and Ozier, Owen W., Can Education be Standardized? Evidence from Kenya (June 5, 2022). University of Chicago, Becker Friedman Institute for Economics Working Paper No. 2022-68. https://bfi.uchicago.edu/working-paper/2022-68/

Abstract: We examine the impact of enrolling in schools that employ a highly-standardized approach to education, using random variation from a large nationwide scholarship program. Bridge International Academies not only delivers highly detailed lesson guides to teachers using tablet computers, it also standardizes systems for daily teacher monitoring and feedback, school construction, and financial management. At the time of the study, Bridge operated over 400 private schools serving more than 100,000 pupils. It hired teachers with less formal education and experience than public school teachers, paid them less, and had more working hours per week. Enrolling at Bridge for two years increased test scores by 0.89 additional equivalent years of schooling (EYS) for primary school pupils and by 1.48 EYS for pre-primary pupils. These effects are in the 99th percentile of effects found for at-scale programs studied in a recent survey. Enrolling at Bridge reduced both dispersion in test scores and grade repetition. Test score results do not seem to be driven by rote memorization or by income effects of the scholarship.

The YouTube recommendation algorithm does push real users into mild ideological echo chambers, where users receive different recommendations distributions, but doesn't happen that many go down `rabbit holes' that lead them to extreme content

Brown, Megan and Bisbee, James and Lai, Angela and Bonneau, Richard and Nagler, Jonathan and Tucker, Joshua Aaron, Echo Chambers, Rabbit Holes, and Algorithmic Bias: How YouTube Recommends Content to Real Users (May 11, 2022). SSRN: http://dx.doi.org/10.2139/ssrn.4114905

Abstract: To what extent does the YouTube recommendation algorithm push users into echo chambers, ideologically biased content, or rabbit holes? Despite growing popular concern, recent work suggests that the recommendation algorithm is not pushing users into these echo chambers. However, existing research relies heavily on the use of anonymous data collection that does not account for the personalized nature of the recommendation algorithm. We asked a sample of real users to install a browser extension that downloaded the list of videos they were recommended. We instructed these users to start on an assigned video and then click through 20 sets of recommendations, capturing what they were being shown in real time as they used the platform logged into their real accounts. Using a novel method to estimate the ideology of a YouTube video, we demonstrate that the YouTube recommendation algorithm does, in fact, push real users into mild ideological echo chambers where, by the end of the data collection task, liberals and conservatives received different distributions of recommendations from each other, though this difference is small. While we find evidence that this difference increases the longer the user followed the recommendation algorithm, we do not find evidence that many go down `rabbit holes' that lead them to ideologically extreme content. Finally, we find that YouTube pushes all users, regardless of ideology, towards moderately conservative and an increasingly narrow range of ideological content the longer they follow YouTube's recommendations.

Keywords: YouTube, Recommendation Algorithms, Echo Chambers, Theory Testing

 

Liberals were more prone than conservatives to perceive a tweet with the opposing political view as a bot

Why Some Are Better than Others at Detecting Social Bots: Comparing Baseline Performance to Performance with Aids and Training. Ryan John Kenny. Carnegie Mellon University PhD Dissertations, May 2022. https://www.proquest.com/openview/a907b0780af36f04b33cb1477c8aadc9/1?pq-origsite=gscholar&cbl=18750&diss=y

Abstract: Social bots have infiltrated many social media platforms, sowing misinformation and disinformation. The harm caused by social bots depends on their ability to avoid detection by credibly impersonating human users. These three studies use a signal detection task to compare human detection of Twitter social bot personas with that of machine learning assessments. Across these studies, we find that sensitivity was (1a) minimal without training or aid, (1b) people were hesitant to respond ‘bot,’ and (1c) people were prone to “myside bias,” judging personas less critically when they shared political views. We also observed (1d) sensitivity improved when a bot detection aid was provided and (1e) when users received training focused on the objectives of social bot creators: to amplify narratives to an extensive social network. When participants labeled a persona a social bot, (2) the probability of their willingness to share its content dropped dramatically. We investigated the relationships between users’ attributes and social bot detection performance and found, (3a) social media experience did not improve detection and at times impaired it; (3b) myside bias affected the sensitivity and criterion used by liberals and conservatives differently; and (3c) analytical reasoning did not improve social bot detection, nor did it mitigate observed myside bias effects, but increased them slightly. We found that (4) people were more concerned about social bots influencing others’ online behaviors than being influenced themselves. Additionally, users’ willingness to pay for a social bot detection aid increased (5a) the more they were concerned about social bots, (5b) the greater their social media experience, (5c) the greater their sensitivity, and (5d) the higher their threshold for responding ‘bot.’ These findings demonstrate the threat posed by social  bots and two interventions that may reduce them.

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Political Values and Political Differences

As participants' political difference (PD) from the persona increased, they were more 

likely to judge it a 'bot,' consistent with myside bias, with a one standard deviation increase in 

PD shifting the intercept by 0.19. The post-hoc model adds participants' self-reported 

political values (PV) as the main effects and interactions. In the post hoc model, both liberal 

and conservative participants had a greater probability of responding ‘bot’ when viewing a 

persona of an opposing political view. However, liberals had a greater probability of 

responding ‘bot’ than conservatives. 

Both models' interaction between bot indicator and political differences (BI x PD) is 

explained by adding political values in the post-hoc model. The significant three-way 

interaction (BI x PV x PD) (p < 0.001) reveals an asymmetric pattern of sensitivity related to

participants’ political views. Figure 2 shows the relationship between PV and BI, with PD 

divided into five levels. In the upper left, when judging personas with similar political views,

liberals were very sensitive to the bot indicator score (red line), while conservatives were not

(purple line). At the other extreme, when judging personas with opposite political views, 

liberals were insensitive to bot indicator scores, while conservatives had a modest sensitivity.

Prenatal maternal stress: Pregnant women especially vulnerable to chronic stress; potential challenging situations such as body image issues, lifestyle changes, fluctuating hormones, induce lasting changes to fetal stress response ("fetal programming")

Prenatal stress perturbs fetal iron homeostasis in a sex specific manner. Peter Zimmermann, Marta C. Antonelli, Ritika Sharma, Alexander Müller, Camilla Zelgert, Bibiana Fabre, Natasha Wenzel, Hau-Tieng Wu, Martin G. Frasch & Silvia M. Lobmaier. Scientific Reports volume 12, Article number: 9341, Jun 4 2022. https://www.nature.com/articles/s41598-022-13633-z

Abstract: The adverse effects of maternal prenatal stress (PS) on child’s neurodevelopment warrant the establishment of biomarkers that enable early interventional therapeutic strategies. We performed a prospective matched double cohort study screening 2000 pregnant women in third trimester with Cohen Perceived Stress Scale-10 (PSS-10) questionnaire; 164 participants were recruited and classified as stressed and control group (SG, CG). Fetal cord blood iron parameters of 107 patients were measured at birth. Transabdominal electrocardiograms-based Fetal Stress Index (FSI) was derived. We investigated sex contribution to group differences and conducted causal inference analyses to assess the total effect of PS exposure on iron homeostasis using a directed acyclic graph (DAG) approach. Differences are reported for p < 0.05 unless noted otherwise. Transferrin saturation was lower in male stressed neonates. The minimum adjustment set of the DAG to estimate the total effect of PS exposure on fetal ferritin iron biomarkers consisted of maternal age and socioeconomic status: SG revealed a 15% decrease in fetal ferritin compared with CG. Mean FSI was higher among SG than among CG. FSI-based timely detection of fetuses affected by PS can support early individualized iron supplementation and neurodevelopmental follow-up to prevent long-term sequelae due to PS-exacerbated impairment of the iron homeostasis.

Discussion

PS disrupts fetal iron homeostasis in a sex-specific manner

This study indicates a sex-dependent difference in fetal iron homeostasis and FSI due to PS in an otherwise healthy cohort, mainly driven by the male sex. Causal inference approach allowed us to independently verify fetal sex as an important effect modifier on the causal pathway between PS and cord blood ferritin. The findings strengthen previous published FSI results10.

The PS effect on the fetal iron biomarkers has been poorly understood. Rhesus monkey infants born to stressed mothers were more likely to develop iron deficiency7. Likewise, several studies in humans have shown a correlation between PS and cord blood zinc protoporphyrin/heme index as well as PS and ferritin levels4,5,6.

During pregnancy, maternal stress hormones such as cortisol influence the growing fetus and its neurodevelopment, presumably via epigenetic mechanisms9,19. Cortes and colleagues proposed an influence of chronic stress through a stress-induced altered expression of a variant of the enzyme acetylcholinesterase on the iron-regulating system in fetal sheep brain-derived primary microglia cultures15. They assumed the afferent cholinergic anti-inflammatory pathway signaling on microglial α7 nicotinic acetylcholine receptors to down-regulate metal ion transporter and ferroportin, which acts as a hepcidin receptor (Fig. 1).

Animal studies observed stress-dependent cognitive deficits mainly seen in males20,21. In humans, sex-specific PS effects are reflected by lower scores in conduct assessments and higher test scores for emotional disturbance in males compared to females13,22,23. Campbell et al. applied six specific PS questionnaires, each twice in the second and third trimester, to 428 ~ 28-years-old mothers and found newborns of pregnant women exposed to violence to be stronger associated with cord blood ferritin levels lower in boys than in girls4.

The relation of iron homeostasis biomarkers to PS

Our results show no relationship between the presence of maternal anemia, fetal iron deficiency and PS. These findings are in agreement with literature suggesting that the fetus is robust against moderate changes of the maternal iron homeostasis24,25.

Within the DAG framework, we estimated that PS reduced the cord blood serum ferritin levels by approximately 15%. These findings are exceeding the adaption factor for inflammatory processes in infants the WHO uses in a current guideline26. We assume that during pregnancy even relatively small additional shifts in fetal iron homeostasis, especially in ferritin levels, may induce sex-specific neurodevelopmental effects27. Our observations regarding the link between PS, fetal iron homeostasis and the postnatal neurodevelopmental trajectories warrant further investigations, because this condition may be corrected therapeutically via targeted prenatal and/or postnatal iron supplementation2.

The PS effect transmitted by maternal cortisol on the fetal neurodevelopment may depend on the time course of exposure28,29. Hypothetically, taking our explanation further antepartum, i.e., to ~ 3.5 weeks earlier at the time of taECG recording, we speculate that PS-induced differences in hepcidin at that time may lead to the reported changes in iron parameters that could still be detected in the cord blood1. Our exploratory findings of higher FSI within certain ranges of at-birth iron biomarkers support this notion. The absence of group differences of cord blood iron parameters including the whole cohort may reflect adaptions (more pronounced in females) that occur as pregnancy progresses20.

The role of the immune system

Our data in leukocytes showed no evidence of increased inflammatory processes in SG neonates (Table S1). Nevertheless, acute inflammatory processes, a common phenomenon during delivery, may have had an effect on our cord blood findings transmitted by other cellular messengers such as the cytokine IL-6 (Fig. 1). In general, inflammation upregulates the acute phase protein ferritin influencing its role as a biomarker of the iron storage30. Inflammation also upregulates hepcidin levels leading to an intestinal sequestration of iron14. Cord blood interleukin levels were increased in chronically stressed mother’s infants31. Taken together, the effects of PS can be mediated by inflammatory processes and this link should be investigated further in future studies including a broader characterization of the maternal and neonatal inflammatory profiles32.

FSI as a potential biomarker of PS in late gestation

The present findings confirm that FSI is increased in PS during the third trimester of pregnancy10. Because the FSI showed poor association with the measured iron biomarkers, we assume that PS influences fHR and mHR coupling by different pathways. Moreover, in our DAG framework it is conceivable that FSI may serve as an indicator of subsequent altered neurodevelopmental trajectories, even in the absence of biochemical PS correlates such as alterations in iron homeostasis33,34.

ML-based predictions of PS

With our ML approach, we mimicked a real-life scenario to identify mother–fetus dyads affected by PS. Our results are consistent with findings in other clinical settings where electronic medical record mining identified patients at risk even without additional biophysical assessments, such as ECG35. Notably, adding biophysical characteristics improves ML model performance, thus emphasizing the potential of antepartum mother–child monitoring using taECG to improve the early detection of health abnormalities such as PS.

Strengths and limitations

Strengths of the FELICITy study are the prospective design preventing recall bias and the definition of criteria for a matching system to exclude possible confounders. Additionally, eventual confounding factors such as the intake of iron supplement and ethnic group showed no group differences (Fig. S1). This is the first prospective longitudinal study starting in utero aiming to assess PS and fetal biomarkers. Additionally, it is the first study to use causal inference and machine learning approaches to investigate sex-dependent influence of PS on the fetal iron homeostasis. There are certain limitations. Our inclusion criteria prevented us from enrolling non-German-speaking patients. This may have biased how the PS effects are represented in the multicultural Munich population. Also, we used a matching system that could not include every screened CG patient. Due to the uncertainties of a human study, several subject numbers for different sub-analyses were lower. Furthermore, we focused on measuring PS in the third trimester which necessarily neglected earlier stages of pregnancy and a possible temporal dynamic of PS over the entire course of pregnancy.

We chose not to include other potential effect modifiers on the causal pathway of the DAG such as inflammatory processes as they are difficult to define quantitatively and were not the focus of this study. However, future studies could further refine estimates of PS → Iron Biomarker average exposure effect by adjusting for these covariates.

This study did not differentiate between arterial or venous origin of the analyzed cord blood samples. To our knowledge this issue has not been addressed in literature so far. In general, the placental iron transfer and the assessment of the fetal iron status using cord blood parameters are poorly understood36,37. As of the date of the manuscript’s submission no commonly used normal ranges of cord blood iron parameters exist. The established ranges start with the child's birth26 but are not applicable to cord blood ranges since in cord blood usually, iron parameters are higher38. These issues warrant further research to identify potential biasing effects on cord blood analysis.