Climate−dependent phosphorus forms and their utilization by plants and microorganisms

Phosphorus (P) in soil is an important nutrient for biological activity and often limits plant and microbial growth in natural ecosystems. Due to its chemical nature and conditions in soil, its mobility in soil is limited by strong sorption to metal(hydr)oxides and precipitation with calcium (Ca), iron (Fe), and aluminum (Al) ions. P speciation and fixation in soil changes during pedogenesis from mainly Ca-bound P in early developmental stages to Fe-, and Al-bound P and organic P in more weathered soils. The rate of mineral weathering and soil development strongly depend on climatic conditions. Therefore, ecosystems under varying climate, but with soils that originate from similar parent material, are expected to show different states of weathering and P speciation in soil. Plants and microorganisms possess adaptations to mobilize P from various sources. It is believed that P cycling mechanisms and processes change with the P species that are available in soil. The aim of this work was to determine climate-dependent P speciation and biotic P cycling strategies along an aridity gradient in the Chilean Coastal Cordillera. The study sites comprised a sequence of ecosystems from an arid shrubland in the north to a Mediterranean woodland as intermediate site and a humid-temperate forest in the south. The studies of this work focused on the question whether P nutrition in a given ecosystem depends mainly on the acquisition of P from mineral sources, or if recycling of organic P is the main P source. Moreover, the focus was on the impact of root-derived labile C on P cycling under varying climatic conditions. The contribution of low-molecular-weight organic acids (LMWOAs) to mineral weathering (weathering agents) but also to organic P recycling was scrutinized. This work consists of four studies that investigated P speciation in soil and the mechanisms driving P cycling within the plant-soil-microbe system. P speciation in the rhizosphere and bulk soil was determined by X-ray absorption near edge structure (XANES), a powerful tool to determine the speciation of inorganic P in soil. Moreover, P was extracted as operationally defined P pools as water extractable, NaHCO3 extractable, ammonium-oxalate extractable (NH4-oxalate), and dithionite-citrate-bicarbonate (DCB) extractable P. The sorption capacity of soils for P was determined by 33P application. The adsorption of the tracer to the soil solid phase was measured and the sorption capacity of soils was calculated. Microbial uptake of sorbed inorganic P was quantified under steady state conditions and under the addition of glucose (rhizosphere conditions). A method to extract low-molecular-weight organic acids was adapted to measure the 13C content in these weathering agents. LMWOA were extracted after 13C enriched CO2 application (pulse labeling). This allowed not only to relate P species to the exudation of organic acids in general, but also to quantify plant and microbial C allocation to these weathering agents. Primary Ca-bound P contents were highest in the arid shrubland ecosystem and declined towards the Mediterranean woodland and humid-temperate forest. Secondary precipitated Fe- and Al-P followed the same trend, while inorganic P sorbed to Fe- and Al-(hydr)oxides and organic P increased with decreasing aridity. Accumulation of organic P in root proximity was detected in the Mediterranean woodland and humid-temperate forest, reflecting high biological activity at these sites. P speciation was correlated with LMWOA contents, phosphatase kinetics and microbial biomass carbon. It was demonstrated, that under arid climate and in the subsoil of the Mediterranean woodland, LMWOA contributed to mineral weathering. They fundamentally changed their role in the Mediterranean woodland’s topsoil and humid-temperate forest soil, where LMWOA liberated organic P, likely for enzymatic degradation. It was inferred that P cycling under arid conditions is driven by the acquisition of mineral inorganic P but towards decreasing aridity, the importance of organic P recycling increases. The P sorption capacity of soils was highest under a humid climate and highly weathered soils and was explained by high contents of ferrihydrite, ammonium-oxalate leachable Al and clay. Microbial uptake of sorbed inorganic P from the soil’s solid phase was highest in the A-horizon of the Mediterranean woodland soil and was low in the humid-temperate forest. In the latter, phosphatase activity was high, indicating organic P recycling and a low relevance of sorbed inorganic P to meet the P requirements of the biota. Inorganic P sorbed to the soil solid phase was most intensively utilized in the Mediterranean woodland soil and microbial uptake of sorbed inorganic P increased when glucose was added. This demonstrates that P limitation in the Mediterranean woodland soil can be reduced when readily available C is exuded in the rhizosphere. In contrast, microbiota in the other ecosystems along the ecosequence were either not primarily P limited or relied on different P sources. Moreover, in the humid-temperate forest a plethora of C compounds are available for microbial utilization, reducing the importance of labile root exuded C. In accordance with the XANES results, operationally defined P pools showed an increase of plant available P and a decrease of precipitated P with decreasing aridity. While the content of LMWOA in soil was higher in the humid-temperate forest than the Mediterranean woodland and arid shrubland, 13C allocation to LMWOA was of equal magnitude in the humid-temperate forest and Mediterranean woodland. High enzyme activities in the humid-temperate forest imply the utilization of organic P. A variety of P mobilizing processes can be assumed as weathering agents were only partly derived from recently exuded root C but also from unlabeled C sources. For the arid shrubland and Mediterranean woodland it was shown that the content of fungi-derived oxalic acid is positively correlated with well crystallized inorganic P (DCB leachable P), XV pointing to fungi as important organisms to mobilize hardly available P sources in these ecosystems. 13C allocation patterns in the arid shrubland are similar to those in the Mediterranean woodland, even though contents are on a lower level. This is interpreted as adaption to drought in both off these ecosystems and an indication that aridity is driving belowground C allocation. In summary it was demonstrated that biological weathering is an important process of P acquisition under arid and Mediterranean climate, but not under humid-temperate climate, where P recycling becomes more important. At the same time, LMWOA are important P cycling agents in soil; under arid conditions they support mineral weathering, while under humid climate they facilitate organic P recycling. C limitation of P acquisition is high under arid and Mediterranean climate and relieved under humid climate. With respect to climate dependent P cycling in soil it is concluded that each site has its specific P speciation, P availability, and stoichiometric nutrient constraints. It was, therefore, not possible to identify a systematic trend of these parameters along the ecosequence. Abiotic changes (i.e., climate change) likely result in nonlinear changes in P speciation, P availability, and stoichiometric nutrient limitations, impeding our ability to predict changes in P cycling as a result of changing abiotic conditions at a site.Phosphor (P) im Boden ist ein wichtiger Nährstoff für die biologische Aktivität, welcher in natürlichen Ökosystemen häufig das Wachstum von Pflanzen und Mikroorganismen limitiert. Aufgrund seiner chemischen Eigenschaften und der physikochemischen Gegebenheiten im Boden ist seine Mobilität im Boden durch starke Sorption an Metall(hydr)oxide und Ausfällung mit Calcium (Ca), Eisen (Fe) und Aluminium (Al) eingeschränkt. Die P-Speziierung und -Fixierung im Boden ändert sich während der Pedogenese von hauptsächlich Ca-gebundenem P in frühen Entwicklungsstadien zu Fe-, und Al-gebundenem- und organischem P in stärker verwitterten Böden. Die Geschwindigkeit der Mineralverwitterung und der Bodenentwicklung hängt stark von den klimatischen Bedingungen ab. Daher ist zu erwarten, dass Ökosysteme mit unterschiedlichem Klima, aber mit Böden, die aus ähnlichem Ausgangsmaterial entstanden sind, unterschiedliche Zustände der Verwitterung und P-Speziierung im Boden aufweisen. Pflanzen und Mikroorganismen verfügen über Mechanismen, um P aus verschiedenen Quellen zu akquirieren. Es wird angenommen, dass sich die biotischen Mechanismen und Prozesse des P-Kreislaufs den im Boden verfügbaren P-Spezies anpassen. Ziel dieser Arbeit war es, die klimaabhängige P-Speziierung und die biotischen P-Mobilisierungsstrategien entlang eines Ariditätsgradienten in der chilenischen Küstenkordillere zu bestimmen. Die Untersuchungsstandorte bildeten eine Ökosystem- Sequenz von einem ariden Strauchland im Norden über ein mediterranes Waldgebiet zu einem feucht-temperierten Wald im Süden. Die Studien dieser Arbeit konzentrierten sich insbesondere auf die Frage, ob die pflanzliche P-Ernährung in einem gegebenen Ökosystem hauptsächlich auf der Aufnahme von P aus mineralischen Quellen beruht oder ob die Mineralisierung von organischem P die Haupt-P-Quelle darstellt. Darüber hinaus lag der Fokus der Arbeit auf den Auswirkungen von aus Wurzeln stammendem leicht verfügbarem Kohlenstoff (C) auf den P-Kreislauf unter variierenden klimatischen Bedingungen. Der Beitrag von niedermolekularen organischen Säuren (LMWOAs) zur mineralischen Verwitterung, aber auch zur Mineralisierung organischen Ps wurde untersucht. Diese Arbeit besteht aus vier Studien, die die P-Speziierung im Boden und die Mechanismen, die den P-Kreislauf innerhalb des Systems Pflanze-Boden-Mikrobe antreiben, untersuchten. Die P-Speziierung in der Rhizosphäre und im Boden wurde mittels Röntgen-Nahkanten-Absorptions-Spektroskopie (XANES) bestimmt, einer leistungsfähigen Methode zur Bestimmung der Speziierung anorganischen Ps im Boden. Darüber hinaus wurde P als Löslichkeits-definierte P-Formen als wasser-extrahierbares-, Natriumhydrogencarbonat-extrahierbares-, Ammonium-Oxalat-extrahierbares- und Dithionit-Citrat-Bikarbonat (DCB)-extrahierbares P bestimmt. Die Sorptionskapazität von Böden für P wurde mittels Applikation von 33P untersucht. Die mikrobielle Aufnahme von sorbiertem anorganischem P wurde unter stationären Bedingungen und unter Zugabe von Glukose (Bedingungen ähnlich denen der Rhizosphäre) quantifiziert. Eine Methode zur Extraktion niedermolekularer organischer Säuren wurde adaptiert, um den 13C-Gehalt in diesen, die mineralische Verwitterung befördernden Stoffen zu messen. LMWOA wurden nach der Applikation von 13C-angereichertem CO2 extrahiert. Dies ermöglichte einerseits P-Spezies mit der Exsudation von organischen Säuren im Allgemeinen in Beziehung zu setzen, und andererseits auch die pflanzliche und mikrobielle C-Allokation zu diesen Verwitterungsmitteln zu quantifizieren. Die primären Ca-gebundenen P-Gehalte waren im ariden Strauchland-Ökosystem am höchsten und nahmen zum mediterranen Waldgebiet und feucht-temperierten Wald hin ab. Sekundär gebundenes Fe- und Al-P folgte dem gleichen Trend, während anorganisches P, das an Fe- und Al-(Hydr)oxiden sorbiert ist, und organisches P mit abnehmender Trockenheit zunahmen. Eine Akkumulation von organischem P in der Nähe der Wurzeln wurde im mediterranen Wald und im feucht-temperierten Wald festgestellt, was eine hohe biologische Aktivität an diesen Standorten widerspiegelt. Die P-Speziierung wurde mit dem LMWOA-Gehalt, der Phosphatase-Kinetik und dem mikrobiellen Biomasse-Kohlenstoff korreliert. Es konnte gezeigt werden, dass LMWOA unter aridem Klima und im Unterboden des mediterranen Waldes zur Mineralverwitterung beitrugen. Ihre Rolle änderte sich jedoch grundlegend im Oberboden des mediterranen Waldes und im Boden des feucht-temperierten Waldes, wo LMWOA organisches P freisetzten, was dann für den enzymatischen Abbau zur Verfügung stand. Daraus wurde gefolgert, dass der P-Zyklus unter ariden Bedingungen durch die Aufnahme von mineralischem, anorganischem P angetrieben wird, mit abnehmender Trockenheit nimmt die Bedeutung der organischen P-Mineralisierung jedoch zu. Die P-Sorptionskapazität der Böden war unter feuchtem Klima und stark verwitterten Böden am höchsten und wurde durch hohe Gehalte an Ferrihydrit, Ammonium-Oxalat-löslichem-Al und Ton erklärt. Die mikrobielle Aufnahme von sorbiertem anorganischem P von der Bodenfestphase war im A-Horizont des mediterranen Waldes am höchsten. Im feucht-temperierten Wald hingegen war die mikrobielle Aufnahme von sorbiertem anorganischem P gering, die Phosphataseaktivität jedoch hoch. Dies deutet auf die Mineralisierung organischen Ps und eine geringe Relevanz sorbierten anorganischem Ps zur Deckung des P-Bedarfs der Pflanzen und Mikroorganismen hin. An die Bodenfestphase sorbiertes anorganisches P wurde im Boden des mediterranen Waldes am intensivsten verwertet und die mikrobielle Aufnahme von sorbiertem anorganischem P erhöhte sich bei Zugabe von Glukose. Dies zeigt, dass die P-Limitierung im mediterranen Waldboden aufgehoben wird, wenn leicht verfügbarer C in der Rhizosphäre ausgeschieden wird. Im Gegensatz dazu waren die Mikroorganismen in den anderen Ökosystemen entlang der Ökosequenz entweder nicht primär P-limitiert oder sie waren auf andere P-Quellen angewiesen. Darüber hinaus ist im feucht-temperierten Wald eine Vielzahl von C-Verbindungen für die mikrobielle Verwertung verfügbar, was die Bedeutung des von Wurzeln ausgeschiedenen Cs reduziert. In Übereinstimmung mit den XANES-Ergebnissen zeigten Löslichkeits-definierte P-Pools eine Zunahme des pflanzenverfügbaren P und eine Abnahme des ausgefällten P mit abnehmender Trockenheit. Während der Gehalt an LMWOA im Boden im feucht-gemäßigten Wald höher war als im mediterranen Wald und im trockenen Buschland, war die 13C-Allokation zu LMWOA im feucht-gemäßigten Wald und im mediterranen Wald gleich groß. Hohe Enzymaktivitäten im feucht-gemäßigten Wald deuten auf die Verwertung von organischem P hin. Es ist anzunehmen, dass in diesem Ökosystem eine Vielzahl von P-mobilisierenden Prozessen anzutreffen ist, da die Verwitterungsstoffe nur teilweise aus kürzlich ausgeschiedenem Wurzel-C, aber auch aus anderen C-Quellen des Bodens stammen. Für das aride Strauchland und die mediterranen Wälder wurde gezeigt, dass der Gehalt an pilzlich erzeugter Oxalsäure positiv mit gut kristallisiertem anorganischem P (DCB lösliches P) korreliert ist, was auf Pilze als wichtige Organismen zur Mobilisierung schwer verfügbarer P-Quellen in diesen Ökosystemen hinweist. Die 13C-Allokation im ariden Strauchland ähnelt derjenigen im mediterranen Wald, auch wenn die Gehalte auf einem niedrigeren Niveau liegen. Dies wird als Anpassung an die Trockenheit in diesen beiden Ökosystemen interpretiert und ist ein Hinweis darauf, dass die Trockenheit die pflanzliche C-Allokation im Boden antreibt. Zusammenfassend wurde gezeigt, dass die biologische Verwitterung ein wichtiger Prozess der P-Gewinnung unter aridem und mediterranem Klima ist, aber nicht unter feucht-gemäßigtem Klima, wo die Mineralisierung organischen Ps eine bedeutende Rolle spielt. Gleichzeitig sind LMWOAs wichtige Stoffe der P Mobilisierung im Boden; unter ariden Bedingungen dienen sie der mineralischen Verwitterung, während sie unter feuchtem Klima die Mineralisierung organischen Ps unterstützen. Die C-Limitierung der P-Aufnahme ist unter aridem und mediterranem Klima hoch und unter feuchtem Klima gering. In Bezug auf den klimaabhängigen P-Kreislauf im Boden wird geschlossen, dass jeder Standort seine spezifische P-Speziation, P-Verfügbarkeit und stöchiometrische Nährstoffverfügbarkeiten hat. Es war nicht möglich, einen systematischen Trend dieser Parameter entlang der Ökosequenz zu identifizieren. Abiotische Veränderungen (d. h. der Klimawandel) führen wahrscheinlich zu nichtlinearen Veränderungen der P-Speziation, der P-Verfügbarkeit und der stöchiometrischen Nährstoffverfügbarkeit, was unsere Fähigkeit zur Vorhersage von Veränderungen des P-Kreislaufs als Folge veränderter abiotischer Bedingungen an einem Standort erschwert

An embedded process perspective

It remains a dogma in cognitive neuroscience to separate human attention and memory into distinct modules and processes. Here we propose that brain rhythms reflect the embedded nature of these processes in the human brain, as evident from their shared neural signatures: gamma oscillations (30–90 Hz) reflect sensory information processing and activated neural representations (memory items). The theta rhythm (3–8 Hz) is a pacemaker of explicit control processes (central executive), structuring neural information processing, bit by bit, as reflected in the theta-gamma code. By representing memory items in a sequential and time-compressed manner the theta-gamma code is hypothesized to solve key problems of neural computation: (1) attentional sampling (integrating and segregating information processing), (2) mnemonic updating (implementing Hebbian learning), and (3) predictive coding (advancing information processing ahead of the real time to guide behavior). In this framework, reduced alpha oscillations (8–14 Hz) reflect activated semantic networks, involved in both explicit and implicit mnemonic processes. Linking recent theoretical accounts and empirical insights on neural rhythms to the embedded-process model advances our understanding of the integrated nature of attention and memory – as the bedrock of human cognition

Cross-Cultural Differences in the Generation of Novel Ideas in Middle Childhood

Innovation and creativity have recently been in the center of the debate on human cultural evolution. Yet, we know very little about childrens’ developing capacity to generate novel ideas, as a key component of innovation and creativity, in different cultural contexts. Here, we assessed 8‐ to 9-year-old children from an autonomous and a relational cultural context, namely Münster (urban Germany; n = 29) and Banten (rural Cameroon; n = 29). These cultural contexts vary largely in their ecology, social structure, and educational system, as well as the cultural models on children’s individual development and thinking. Therefore, they provide an optimal contrast to investigate cultural similarities and differences in development of creative capacities. We applied classical divergent thinking tasks, namely an alternative uses task and a pattern association task. In these tasks, children are asked to generate as many ideas as possible what an object could be used for or what a pattern could be. First, our study revealed a good internal consistency and inter-task correlations for the assessment of children’s fluency and the generation of unique ideas in both cultures. Second, and most critically, we found significantly higher levels of creative capacities in children from Münster in contrast to Banten. This was reflected in both a higher number of ideas (fluency) and a higher number of unique ideas (uniqueness). Third, looking at the type of answers that children gave in the alternative uses task, we found that children from Münster and Banten uttered a similar number of conventional ideas, but that children from Münster uttered more ideas to manipulate an object, invent novel things with an object, and involve an object in play or pretend play, or in a fantasy story. This demonstrates that early creative development is strongly influenced by the cultural context and substantiates the cultural nature of human cognitive development

Cognitive and motivational underpinnings of early helping behavior

Frühes Hilfeverhalten scheint eine einfache Handlung zu sein, es ist jedoch ein komplexes Phänomen. Warum beginnen Säuglinge schon früh in ihrem zweiten Lebensjahr anderen zu helfen, zum Beispiel, wenn diese ein Objekt nicht erreichen können, nach dem sie sich ausstrecken? Wie nehmen sie Situationen wahr in denen andere ein Bedürfnis haben, wie verstehen sie ihre eigene Rolle in diesen Situationen (kognitive Grundlagen) und was motiviert ihre Hilfsbereitschaft in diesen Situationen (motivationale Grundlagen)? In dieser Synopse, bette ich die Forschungsarbeiten meiner Dissertation in einen breiteren empirischen und theoretischen Kontext, ein. Hierzu organisiere ich aktuelle Themen und Forschungsarbeiten entlang vier allgemeiner Faktoren, die das frühe Hilfeverhalten beeinflussen. Diese umfassen sozial-kognitive Funktionen (z. B. das Verständnis über die Hilfsbedürftigkeit anderer und über die eigenen Fähigkeiten, helfen zu können), die Sozialisation im kulturellen Kontext (z. B. die mütterliche Vermittlung alltäglicher Aufgaben), Einflüsse der sozialen Situation (z. B. vorherige Interaktionen mit der bedürftigen Person) und die erwarteten Konsequenzen früher Hilfehandlungen (z. B. Lob und Dank durch die Eltern). Schließlich wende ich mich den biologischen Grundlagen frühen Hilfeverhaltens zu. Einerseits, wieso sich Hilfsbereitschaft evolutionär entwickelt haben könnte und andererseits, wie früher Hilfeverhalten in proximalen biologischen Mechanismen verankert sein könnte. Dies bringt mich zu dem Schluss, dass, auch wenn die Frage nach der Existenz einer frühen, altruistischen Motivation ungelöst bleibt, frühes Hilfeverhalten tief in unserer sozialen Natur verankert ist.Infants’ helping behavior appears to be a simple action, but it is a complex phenomenon. Why do infants spontaneously start to help others at the beginning of their second year of life, for example, when another individual is reaching for an object that she cannot reach? Put differently, how do infants perceive situations and their own role in situations in which another individual is in need for help (cognitive underpinnings) and what motivates them to engage helpfully in these situations (motivational underpinnings)? In this synopsis, I embed the empirical works of my dissertation in a broader empirical and theoretical context. In particular, I will organize recent topics and research about infants’ helping behavior along four general factors that influence infants helping behavior in a certain situation. These comprise socio-cognitive functions (e.g., understanding others’ needs and the own competencies to engage helpfully), the socialization within the cultural context (e.g., maternal scaffolding of chores), influences of the social situation (e.g., recent social interactions with the recipient), and expected consequences of helpful behavior (e.g., praise and thanking by the parents). I will then discuss the biological foundations of infants’ early motivation to help. That is, why helping behavior may have evolved and how early helping behavior may be grounded in proximate biological mechanisms. I will conclude that, although the debate about infants’ altruistic tendencies remains unresolved, early helping behavior is certainly deeply grounded in our social human nature

Young Children Respond to Moral Dilemmas Like Their Mothers

There is a large scientific interest in human moral judgments. However, little is known about the developmental origins and the specific role of the primary caregivers in the early development of inter-individual differences in human morality. Here, we assess the moral intuitions of 3- to 6-year-old children and their mothers (N = 56), using child-friendly versions of five trolley dilemmas and two control scenarios. We found that children responded to moral dilemmas similar to their mothers, revealed by correlations between the responses of mothers and their children in all five moral dilemmas and a highly similar overall response pattern between mother and child across all judgments. This was revealed by a high agreement in the response pattern of children and their mothers. Furthermore, children’s overall response tendencies were similar to the response tendencies of adults. Thus, similar moral principles (e.g., the Doctrine of the Double Effect) which have been identified in adults, and describes as a universal moral grammar, may guide the moral intuitions in early childhood already. Taken together, the present findings provide the first evidence that children’s moral intuitions are closely associated with the moral intuitions of their mother

The Development of Context-Sensitive Attention Across Cultures: The Impact of Stimulus Familiarity

Across cultures, there are marked differences in visual attention that gradually develop between 4 and 6 years of age. According to the social orientation hypothesis, people in interdependent cultures should show more pronounced context sensitivity than people in independent cultures. However, according to the differential familiarity hypothesis, the focus on the salient object should also depend on the familiarity of the stimulus; people will focus more on the focal object (i.e., less context sensitivity), if it is a less familiar stimulus. To examine the differences in visual attention between interdependent and independent cultures while taking into account stimulus familiarity, this study used an eye-tracking paradigm to assess visual attention of participants between 4 and 20 years who came from urban middle-class families from Germany (n= 53; independent culture) or from Nso families in a rural area in Cameroon (n= 50; interdependent culture). Each participant saw four sets of stimuli, which varied in terms of their familiarity: (1) standard stimuli, (2) non-semantic stimuli, both more familiar to participants from Germany, (3) culture-specific matched stimuli, and (4) simple stimuli, similarly familiar to the individuals of both cultures. Overall, the findings show that mean differences in visual attention between cultures were highly contingent on the stimuli sets: In support of the social orientation hypothesis, German participants showed a higher object focus for the culture-specific matched stimuli, while there were no cultural differences for the simple set. In support of the differential familiarity hypothesis, the Cameroonian participants showed a higher object focus for the less familiar sets, namely the standard and non-semantic sets. Furthermore, context sensitivity correlated across all the sets. In sum, these findings suggest that the familiarity of a stimulus strongly affects individuals' visual attention, meaning that stimulus familiarity needs to be considered when investigating culture-specific differences in attentional styles

Communicative signals during joint attention promote neural processes of infants and caregivers

Communicative signals such as eye contact increase infants’ brain activation to visual stimuli and promote joint attention. Our study assessed whether communicative signals during joint attention enhance infant-caregiver dyads’ neural responses to objects, and their neural synchrony. To track mutual attention processes, we applied rhythmic visual stimulation (RVS), presenting images of objects to 12-month-old infants and their mothers (n = 37 dyads), while we recorded dyads’ brain activity (i.e., steady-state visual evoked potentials, SSVEPs) with electroencephalography (EEG) hyperscanning. Within dyads, mothers either communicatively showed the images to their infant or watched the images without communicative engagement. Communicative cues increased infants’ and mothers’ SSVEPs at central-occipital-parietal, and central electrode sites, respectively. Infants showed significantly more gaze behaviour to images during communicative engagement. Dyadic neural synchrony (SSVEP amplitude envelope correlations, AECs) was not modulated by communicative cues. Taken together, maternal communicative cues in joint attention increase infants’ neural responses to objects, and shape mothers’ own attention processes. We show that communicative cues enhance cortical visual processing, thus play an essential role in social learning. Future studies need to elucidate the effect of communicative cues on neural synchrony during joint attention. Finally, our study introduces RVS to study infant-caregiver neural dynamics in social contexts

The Development of Context-Sensitive Attention in Urban and Rural Brazil

Human perception differs profoundly between individuals from different cultures. In the present study, we investigated the development of context-sensitive attention (the relative focus on context elements of a visual scene) in a large sample (N= 297) of 5- to 15-year-olds and young adults from rural and urban Brazil, namely from agricultural villages in the Amazon region and the city of Sao Paulo. We applied several visual tasks which assess context-sensitive attention, including an optical illusion, a picture description, a picture recognition and a facial emotion judgment task. The results revealed that children and adults from the urban sample had a higher level of context-sensitive attention, when compared to children and adults from the rural sample. In particular, participants from Sao Paulo were more easily deceived by the context elements in an optical illusion task and remembered more context elements in a recognition task than participants from rural Amazon villages. In these two tasks, context-sensitivity increased with age. However, we did not find a cultural difference in the picture description and the facial emotion judgment task. These findings support the idea that visual information processing is highly dependent on the culture-specific learning environments from very early in development. Specifically, they are more consistent with accounts that emphasize the role of the visual environment, than with the social orientation account. However, they also highlight that further research is needed to disentangle the diverse factors that may influence the early development of visual attention, which underlie culture-specific developmental pathways

Cultural background shapes spatial reference frame proclivity

Spatial navigation is an essential human skill that is influenced by several factors. The present study investigates how gender, age, and cultural background account for differences in reference frame proclivity and performance in a virtual navigation task. Using an online navigation study, we recorded reaction times, error rates (confusion of turning axis), and reference frame proclivity (egocentric vs. allocentric reference frame) of 1823 participants. Reaction times significantly varied with gender and age, but were only marginally influenced by the cultural background of participants. Error rates were in line with these results and exhibited a significant influence of gender and culture, but not age. Participants’ cultural background significantly influenced reference frame selection; the majority of North-Americans preferred an allocentric strategy, while Latin-Americans preferred an egocentric navigation strategy. European and Asian groups were in between these two extremes. Neither the factor of age nor the factor of gender had a direct impact on participants’ navigation strategies. The strong effects of cultural background on navigation strategies without the influence of gender or age underlines the importance of socialized spatial cognitive processes and argues for socio-economic analysis in studies investigating human navigation.This work was funded by the European research grant: ERC- 2010-AdG #269716 – MULTISENSE, together with the Cognition and Neuroergonomics/Collaborative Technology Alliance #W911NF-10-2-0022

The proximate regulation of prosocial behaviour: towards a conceptual framework for comparative research

Humans and many other animal species act in ways that benefit others. Such prosocial behaviour has been studied extensively across a range of disciplines over the last decades, but findings to date have led to conflicting conclusions about prosociality across and even within species. Here, we present a conceptual framework to study the proximate regulation of prosocial behaviour in humans, non-human primates and potentially other animals. We build on psychological definitions of prosociality and spell out three key features that need to be in place for behaviour to count as prosocial: benefitting others, intentionality, and voluntariness. We then apply this framework to review observational and experimental studies on sharing behaviour and targeted helping in human children and non-human primates. We show that behaviours that are usually subsumed under the same terminology (e.g. helping) can differ substantially across and within species and that some of them do not fulfil our criteria for prosociality. Our framework allows for precise mapping of prosocial behaviours when retrospectively evaluating studies and offers guidelines for future comparative work