Development of Primal World Beliefs Free

Developmental science has a long history of studying children’s beliefs. For example, false belief tasks are a cornerstone of studying children’s theory of mind (the understanding that others can have beliefs that differ from one’s own) (Wellman, 2018). Major theories of both cognitive and social development also incorporate the study of children’s beliefs. For example, Piaget’s (1954) classic stage theory of cognitive development encompasses an increasingly sophisticated series of beliefs about the world that children progressively master (e.g., object permanence, conservation of matter), and attachment theory emphasizes that children’s internal working models of social relationships (i.e., beliefs about how others will behave and how they can expect to be treated) are shaped by early relationships with important caregivers (Bowlby, 1969).

Developmentalists have examined how environmental stressors are related to children’s beliefs (e.g., Seider et al., 2019, in relation to Black and Latinx adolescents’ experiences of racism; Spencer, 1986, in relation to Atlanta’s missing and murdered children crisis between 1979 and 1981). Children’s beliefs have also been examined in several other specific domains, such as religious beliefs (Davoodi & Clegg, 2022), beliefs about luck (Woolley & Kelley, 2020), beliefs about whether abilities are fixed or malleable with effort (Rege et al., 2021), and beliefs about death (Harris, 2018). However, developmental science has not yet tackled the question of how children develop beliefs about the nature of the world as a broad concept. Is the world a good place? Safe or dangerous? Enticing or dull? Alive or mechanistic? This article aims to introduce developmental scientists to an emerging body of theory and research on primal world beliefs (hereafter referred to as primals) to stimulate future research on how primals are formed.

A first reason for developmentalists to study primals is that primals appear to be closely tied to well-being. For example, a correlation of 0.60 has been reported between seeing the world as good and well-being, which is the same magnitude of correlation as between planet surface temperature and distance from the equator (Clifton et al., 2019). Major models of the role of beliefs and mindsets in well-being, such as cognitive theories of depression, suggest primals may play a causal role in relation to well-being (Clark & Beck, 2010). Thus, it is important for clinicians, parents, and others to learn how primals develop. A second reason for developmentalists to study primals is to understand predictors of primals. Ideas in the primals literature to date have often not been empirically supported. For example, the initial evidence suggests that the hypothesis that positive primals may reflect having led a privileged life is not supported by the data (Kerry et al., 2023; Ludwig et al., 2023). Developmental methods enable the study of the origins of primals, making it important to bring developmental scientists to the table in this emerging area of inquiry.

Primals were initially introduced in social and personality psychology to understand beliefs about the world as a whole (vs. beliefs about the self) that may influence well-being and personality (Clifton et al., 2019). Initial work to identify candidate primals began with ten interrelated projects, such as an analysis of >80,000 tweets beginning with the phrase “the world is” and an analysis of >1,700 descriptions of the world in 385 influential Western and non-Western sacred texts, philosophical treatises, novels, political speeches, and films (Clifton et al., 2019). Efforts reached saturation where, despite more searching, further candidate primals could not be found. A pool of 234 items reflecting possible primals were subjected to three rounds of factor analysis and other analytics, revealing several dimensions (Fig. 1). One overarching primal, good, characterizes individuals’ belief that the world is a good (rather than bad) place. A more granular categorization includes three secondary primals: safe, enticing, and alive. Together, these three primals account for why most people see the world as an overall good or bad place (Clifton & Yaden, 2021). An even finer-grained analysis reveals 17 additional tertiary primals, which cluster under safe, enticing, and alive, and five additional primals that are unrelated to seeing the world as good or bad. Primals reflect beliefs about average tendencies rather than monolithic claims about what everything is like all the time; in other words, primals are conceptualized as continuous rather than dichotomous.

Importantly for developmentalists, the primal framework was derived mainly from what adults rather than children believe about the world. In addition, the concept of “the world” likely varies so that in the initial methodological work, some people whose tweets were analyzed were thinking of the world in physical terms, whereas others were thinking of the world in social, emotional, or existential terms, which may be reflected differently across primals. It is important to recognize that some of the concepts underlying primals are sophisticated and themselves are likely to develop over time. Even for the overarching primal good, a 2-year-old’s understanding of good is quite different from an 18-year-old’s understanding, making it important to understand what is behind each belief and at what age different primals emerge.

In addition, the term “primal” might imply that a belief is “in” the child from infancy, although the term was not intended that way by the researchers who developed this field of research. A key role for developmentalists is to understand how primals develop, perhaps as a function of personal experiences and world views imparted through socialization in particular cultural and historical contexts. Early in development, for example, infants’ movements of their bodies in space affect their perceptions of the world (Lakoff & Johnson, 2003). As children are socialized in particular cultural contexts, they come to take on beliefs that encompass spirituality and other notions of how and why the world operates as it does (Davoodi & Clegg, 2022). To understand primals in adulthood, it is important to understand the early forms of these primals themselves as well as how they evolve into later forms.

Prior to the introduction of the primals framework, belief in a just world was the conceptual and empirical grounding of the bulk of research on individuals’ beliefs about the world as a whole. Early just world theory conceptualized beliefs that the world is just essentially as a coping mechanism that would allow individuals to function in a world where bad things happen by believing that people generally get what they deserve or that everything happens for a reason (Lerner & Miller, 1978). This line of research has treated belief in a just world sometimes as an outcome predicted by earlier life experiences (e.g., what might predict individual differences in just world beliefs) and sometimes as a predictor of other aspects of psychological well-being (Hafer & Bègue, 2005). Recent just world theory and research have highlighted how individuals’ justice-related experiences are directly connected to individuals’ belief in a just world (Thomas, 2022). For example, “justice capital” reflects individual differences in access to justice based on a combination of individual factors (e.g., race, ethnicity, immigration status) and societal structural factors (e.g., racism, discrimination, power). These factors operate together so that some individuals are more likely to be treated justly by authority figures and have other justice-related experiences that would be expected to be directly related to the development of their belief in a just world (Thomas, 2022). Primals research expands beyond the belief that the world is just, to include a number of other beliefs about the world.

An initial study suggests that primals are as stable over time as personality traits (Clifton et al., 2019) and are correlated with well-being variables, such as life satisfaction and depression, and with personality variables, such as optimism (Clifton & Meindl, 2022; Stahlmann et al., 2020). Understanding primals may be useful in several subdisciplines of psychology, as primals predict a range of meaningful outcomes. For example, in political psychology, hierarchical world belief explains 20 times more variance in political ideology than dangerous world belief (Clifton & Kerry, 2022). Parallels may exist between how values and primals are related to specific behaviors, in that both are broad frameworks that may be distal in causal chains leading to eventual behaviors. For example, motivational value types, such as achievement, benevolence, conformity, and so forth (Schwartz, 1992), sometimes have small effect sizes in relation to specific behaviors because a number of other factors, such as costs and incentives, also affect whether values are put into action (Turaga et al., 2010). Yet, values are considered important to understanding human development, and the concept of primals may likewise be useful for developmentalists.

On one hand, evidence about the influence of socializing agents such as parents, teachers, and peers in the development of children’s domain-specific beliefs suggests that the development of primals may hinge on socialization. For example, when children learn about their families’ religious beliefs about deities or about scientific evidence for invisible gases and other phenomena they cannot directly observe, children change even their counterintuitive and counter-perceptual beliefs in response to new information from parents and teachers (Lane, 2018). Beliefs about the appropriateness and desirability of risky behaviors are often socialized by peers during adolescence (Kornienko et al., 2020). Children’s beliefs are also shaped by the cultural contexts in which they live as they internalize cultural norms and expectations (Lansford et al., 2018). For example, children’s beliefs about fairness (Blake et al., 2015) and a number of other beliefs are shaped through cultural learning in which children imitate and conform to normative beliefs within their cultural group (Tomasello, 2016).

On the other hand, beliefs do not always align with socialization experiences or objective reality. For example, adolescents can feel safe even in neighborhoods with high crime rates (Zuberi, 2018). Body image can be distorted, such that adolescents with eating disorders may believe themselves to be overweight even when they are objectively underweight (Sattler et al., 2020). Even attachment relationships are not as stable over time as previously believed (Fearon & Roisman, 2017). Temperament (Chen et al., 2019), polygenic scores (Elam et al., 2021), and other risk and protective factors can moderate associations between a range of experiences and developmental outcomes. Primals, too, may not be directly predictable from particular experiences.

Clifton (2020) offers two theoretical perspectives on primals that generate competing hypotheses that can be tested by developmentalists. First, the interpretive theoretical perspective holds that primals are lenses through which experiences are understood but that the experiences themselves do not shape the primals. This perspective leads to the hypothesis that experiences during childhood and adolescence will not strongly predict the development of primals in a systematic way because individuals would be expected to use past experiences to justify whatever primal they hold, but not as much to use past experiences to shape the emergence of that primal. This interpretative perspective is akin to the idea of schemas, which, once acquired, are used as a shortcut for understanding a situation and determining how to behave when encountering novel situations in the future (Huesmann, 2018). When individuals have an experience or gain information that contradicts their schema, they often ignore, reject, or reframe the experience or information. When individuals have an experience or gain information that supports their schema, they tend to use that experience or information to reinforce their schema and justify why they hold it. Second, and by contrast, the retrospective theoretical perspective holds that previous experiences shape primals that reflect those experiences. The retrospective perspective suggests that experiences during childhood and adolescence will predict the development of primals. For example, neighborhood danger and harsh parenting experienced in childhood and adolescence would be hypothesized to predict low scores on the safe primal (i.e., the belief the world is dangerous), and low socioeconomic status in childhood and adolescence would be hypothesized to predict low scores on the abundant primal (i.e., the belief the world is barren with few opportunities and resources). These hypotheses are consistent with prior work on how traumatic experiences are related to the development of individuals’ schemas about themselves and the world (Janoff-Bulman, 1989) and how justice capital is related to beliefs in a just world (Thomas, 2022). Retrospective explanations of the development of primals involve direct links between experiences in the domain of the primal and the primal itself, such as experiencing abundance and holding the belief that the world is abundant. The retrospective explanation would not be supported by personal experience of abundance, for example, impacting other primals, such as belief that the world is just.

These theoretical perspectives leave open the possibility that life experiences may influence primals in ways not encompassed by retrospective or interpretive theories, such as if watching a movie, being a student, or having a particular job changes one’s beliefs about the world in ways that do not have a direct link between a specific experience (e.g., being victimized in a crime) and a specific primal related to that experience (e.g., believing that the world is a dangerous place). Of course, different types of experiences may be stronger or weaker predictors of the development of primals. For example, the direct experience of being robbed may be more strongly related to the development of the dangerous primal than witnessing someone else be robbed, which in turn might be a stronger predictor than an even more indirect experience such as watching a film in which someone is robbed. Other experiences may take the form of direct instruction about beliefs or being reared in a particular culture in which beliefs are communicated implicitly. Retrospective and interpretive theories should not be treated as exclusive or exhaustive categories, as experiences may still shape primals in ways not defined by these two theories.

Correlations between a variety of experiences and primals suggest more initial support for the interpretive than retrospective theoretical framework (Clifton, 2020; Kerry et al., 2023). For example, growing up in a poorer household, being currently poorer, and living in a poorer neighborhood are only weakly related to seeing the world as less abundant or pleasurable, and even experiencing serious illness such as cystic fibrosis and cancer was either unrelated or only weakly related to seeing the world as a good, safe, or just place (Kerry et al., 2023). However, these correlations were cross-sectional and therefore do not reflect change over time or countless factors that might affect associations between experiences during childhood and adolescence and the development of primals. In a longitudinal quasi-experiment in the USA that included reports of primals both before and after the onset of the COVID-19 pandemic, adults, on average, showed no changes in 23 of the 26 primals, including safe, despite the world’s becoming objectively less safe during that time (Ludwig et al., 2023). These studies suggest that primals are stable frameworks in which people interpret the world. Yet, questions remain: If the content of our primals does not directly correspond to the content of our experiences, then how are primals formed? Might experience shape primals in more oblique ways?

Research to date on the origins of primals is meager. Two gaps in the primal literature are particularly noteworthy for developmentalists. First, we do not yet have validated measures of primals to use with children or adolescents. Rigorous methodological work, such as that conducted with adult samples to develop the primals inventory used with adults (Clifton et al., 2019), is essential for developmental work on primals to proceed. Second, primals have been shown to be fairly stable across two timepoints in test-retest studies (Clifton et al., 2019), but other longitudinal research on primals has not yet been conducted. Developmental scientists might suggest theories in addition to the retrospective and interpretive theories proposed by Clifton (2020) to account for how and why experiences shape primals, and longitudinal developmental research may be especially useful in examining temporal relations between potential predictors and the development of primals. In addition, primals are not conceptually independent of one another. For example, pleasurable, beautiful, and meaningful, are likely not completely disconnected, raising the question of whether they develop independently or whether one is built on the others.

In addition to advancing understanding of how primals are formed, developmental scientists can examine what effect holding each of the 26 primals has for subsequent development. For example, how strong is the connection between the belief that the world is improvable and individuals’ behaviors, such as environmental activism related to improving the word, or the connection between the belief that the world is interesting and eagerness to try new experiences. If primals do have an effect on individuals’ subsequent behaviors, are there particular situational variables that magnify or diminish the effects of primals? Developmental scientists are well-poised to address questions related to moderators and mediators of links between primals and subsequent behavior.

Parents often believe that teaching their children that the world is a bad place is an adaptive way to socialize children. In a study of parents (45% Black, 28% Hispanic, 9% white, 17% mixed or other; median family income = $80,000) recruited from a youth advancement program in New York City, 53% of parents wanted their children to think of the world as a dangerous place, and only 8% of parents thought that having their children see the world as very safe was best for their children (Clifton & Meindl, 2022). When parents hold these beliefs and want to convey them to their children, they likely do so with good intentions – to make their children cautious about real dangers in the world and thereby protect them. Indeed, in some communities and for some individuals, the world is objectively more dangerous than for others, and children need to develop survival strategies to cope with the world in which they live (Henry et al., 2019). We do not yet know whether parents’ socialization messages about the world being a dangerous place lead to the development of negative primals in adulthood, but research on how primals develop is essential because in adulthood, negative primals (e.g., believing the world is a dangerous place) are related to negative outcomes, including worse health, less job and life satisfaction, more depressed affect, and more suicide attempts (Clifton & Meindl, 2022). How can the development of primals be considered in the context of some classic theories of development? We acknowledge that these classic developmental theories, presented briefly here without detailed reviews of their lengthy histories and nuances, apply to many personality variables and social psychological constructs, but we consider them here in relation to the development of primals. We also acknowledge that these theories are not mutually exclusive. These and other theoretical perspectives should be used in conjunction with each other to provide a richer understanding of human development.

According to social information processing theory, children progress through a series of cognitive steps when they encounter information in the social world (Crick & Dodge, 1994). Early experiences shape children’s social information processing, such that children who have been abused by parents (Alink et al., 2019) or rejected by peers (McDonald & Asher, 2018), for example, develop biased ways of processing social information (e.g., believe that others acted with hostile intent even when benign or neutral explanations exist). Primals may develop in similar ways and may be closely related to these biases. That is, through experiencing danger or hostility, children may come to believe that the world is dangerous rather than safe, and this dangerous primal persists, even if the environment changes and is no longer objectively dangerous. For example, a child who is abused at home might become highly vigilant for cues that signify a parent is becoming violent. This vigilance might allow the child to flee if possible, and having a benign or neutral explanation for the parents’ behavior would not be adaptive in this case. However, hypervigilance and hostile attributions are no longer adaptive when the child is no longer in a violent environment. There are emotional, physiological, and attentional costs to hypervigilance, so the degree to which the environment is violent in terms of frequency or severity may not justify these costs.

Likewise, it is possible that primals may serve as useful heuristics for interpreting experiences in particular contexts but become less useful if the parameters of the contexts in which primals were formed no longer hold. For instance, how much of an unfair place does the world need to be such that the belief that the world is an unfair place is actually a net advantage? A social information processing perspective might be consistent with the retrospective theory of primals in their original formation (if experiences during childhood and adolescence predict the development of primals), but once established, primals might be consistent with the interpretive theory (if individuals continue to interpret the world in the context of their existing primals rather than adjusting the primals over time).

A cornerstone of attachment theory is that children develop internal working models of relationships through their early attachments to caregivers. Responsive, sensitive caregiving promotes secure attachment, which contributes to the development of internal working models in which children feel worthy of love and believe that other people can be trusted. By contrast, inconsistent or neglectful caregiving leads to insecure attachment, which contributes to the development of internal working models in which children feel rejected and believe that other people will not reliably meet their needs. From this perspective, primals may develop along with other internal working models. For example, when children with secure attachments develop beliefs that others are trustworthy, they may also develop beliefs that the world is safe and enticing, whereas when children with insecure attachments develop beliefs that they cannot count on others to meet their needs, they may also develop beliefs that the world is dangerous and dull. Secure attachment relationships have been related to a range of positive outcomes, including better social competence and fewer externalizing behavior problems (Fearon & Roisman, 2017); more positive primals may be consistent with this constellation of other positive developmental outcomes. However, even children who had insecure attachments to caregivers can develop secure attachments to romantic partners or close friends later in life (Fraley, 2019). Thus, primal beliefs, too, may change if individuals’ relationships change enough to alter their internal working models.

From the time of the classic Bobo Doll experiments demonstrating that children can learn new behaviors simply by watching other people (Bandura et al., 1961), developmentalists have studied ways in which children learn through observation, reinforcement, and direct instruction. Parents, for example, may model beliefs (e.g., hypervigilance to threats), emotions (e.g., anger), and behaviors (e.g., aggression) that children observe and emulate (Rudolph et al., 2017). Parents also direct children’s attention by pointing out threats and opportunities in their environment. In the case of primals, parents may model their own beliefs about the world in what they say to their children and in how they behave toward their children, so children’s primals would be expected to correlate with their parents’ primals, but these correlations are not yet known. Parents may also reinforce children’s primals by praising particular beliefs that children express, and may also provide direct instruction (e.g., telling their children that the world is a certain way). Primals may also be modeled and reinforced by other socializing agents, including peers, teachers, and the media (such as when playing violent video games or using a mindfulness app).

An important characteristic of ecological models of development is that they include a constellation of proximal and distal systems that jointly affect child development. For example, microsystems of parent-child and peer relationships affect children directly; mesosystems that involve parents’ work influence children indirectly primarily through their influence on parent-child relationships. Exosystems involving neighbors and mass media, macrosystems involving cultural ideologies, and chronosystems involving time all influence children by providing broad contexts in which development occurs (Bronfenbrenner & Morris, 2006). Situating the development of primals in the context of an ecological model suggests that primals are influenced not just by proximal influences of parents and peers as socializing agents with whom children have the most direct contact but also through a whole network of more distal influences. For example, exposure to news media depicting catastrophes in the world, living in a culture in which equality is promoted or in which honor is highly valued, or experiencing major historical events (such as the Great Depression or the COVID-19 pandemic) at particular points in development are all possible influences on the development of primals.

Developmental theories propose how gene × environment interactions may affect child development. Biological sensitivity to context and differential susceptibility models describe how certain phenotypes make some children more sensitive to environmental experiences, which can lead to especially negative outcomes in the face of environmental adversity and especially positive outcomes in the face of environmental support (Belsky & van IJzendoorn, 2017; Ellis & Boyce, 2008). These theories have used the analogy of a dandelion, which can grow anywhere with very little support required, and an orchid, which can thrive beautifully if tended carefully in an optimal environment but will not survive without an optimal environment (although this is an oversimplification, and children may fall anywhere on a continuous spectrum) (Lionetti et al., 2018). Considered in the context of these models, it is possible that children’s biological sensitivity may moderate associations between their environmental experiences and the development of primals. That is, in some children, primals may be more susceptible to environmental influence than others. Like dandelions, some children may perceive the world as safe, enticing, and alive (or dangerous, dull, and mechanistic) regardless of their early experiences, whereas other children, like orchids, may regard the world as safe, enticing, and alive only if their early experiences support these beliefs but otherwise regard the world as dangerous, dull, and mechanistic.

Children are not passive recipients of environmental influences. Instead, children actively elicit certain environmental inputs and mutually influence others in transactional interactions over time (Sameroff, 2009). For example, just as parents socialize their children through the types of opportunities and discipline they provide, children with different behavioral proclivities elicit different responses from their parents. Infants and toddlers with fearful temperaments, for example, may elicit more protective responses from caregivers than infants and toddlers with bolder temperaments, who may elicit more boisterous responses and encouragement from caregivers to play more independently. Over time, more fearful children may also choose different kinds of environments than bolder children (e.g., solitary play vs. playing in larger groups; “niche-picking”), and these chosen experiences influence subsequent development. These transactional models are also consistent with the idea of developmental cascades that capture complex interactions between the developing person and different environmental systems over time (Masten & Cicchetti, 2010). In terms of primals, children’s initial temperamental (e.g., fearful) dispositions may lead to treatment by caregivers and selection of environments that reinforce their initial dispositions, and to the development of primals consistent with their dispositions and experiences (e.g., the world is a dangerous place).

The classic developmental theories summarized above suggest that a retrospective perspective might be more supported than an interpretive perspective on the initial development of primals but that, once established, primals might function interpretively as a way to understand the world, much like schemas do. To date, research on primals has been conducted by personality and social psychologists. Depending on what developmental scientists learn in future research about how primals are formed, and whether longitudinal studies show more support for interpretive, retrospective, or other theoretical perspectives, primals may be a useful construct to include in interventions designed to alter developmental trajectories. For example, the Promoting Alternative Thinking Strategies (PATHS) curriculum, implemented in classrooms to teach children social information processing skills that will help them avoid hostile attribution biases and generate nonaggressive solutions in provocative social situations, has been effective in reducing children’s antisocial behavior and improving peer relationships (Kusché, 2020). Likewise, cognitive behavioral therapy that focuses on reappraisals (specifically changing beliefs) has been effective in reducing anxiety and depression (Kazantzis et al., 2018). Thus, some of the most successful interventions aimed at altering children’s life trajectories have done so by targeting interpretive bias and appraisals, which may be related to beliefs. Using knowledge about these other successful interventions, it may be possible to design interventions to teach parents how to socialize positive primals or to teach children to reframe negative primals and espouse positive primals.

In these efforts, the focus should not always be on safe world belief. Enticing world belief is an equally powerful predictor of well-being (Clifton & Meindl, 2022) and appears to be uniquely related to a variety of behaviors and character strengths, including curiosity (Stahlmann et al., 2020). Other world beliefs may be equally important to foster, such as if a Just world belief corresponds with the development of ethical behavior.

The Positive Psychology Center at the University of Pennsylvania has a list of over 45 laboratories around the world with active research studies on how primals are related to a wide range of topics, including authoritarianism, well-being, altruism, genetics, and more. Given the considerable, burgeoning research on primals, our hope is that outlining how the study of primals fits with classic developmental theories, and illustrating hypotheses about the development of primals that would be generated through different conceptual frameworks, will help ground and guide this emerging literature. We also hope to catalyze future research on the development of primals, which is just now beginning. Developmentalists have much to offer this emerging line of research. Most broadly, how are primals formed? Is there a critical period for the development of primals? How stable are primals over time? Are different primals differentially malleable over time? Do primals predict development over and above other well-studied developmental constructs, such as hostile attribution biases and secure attachment? Using longitudinal data, developmentalists can test hypotheses regarding whether experiences during childhood and adolescence predict the development of primals and, if so, which predictors matter the most for which primals. Developmentalists can also test whether genetic or other risk and protective factors moderate links between early experiences and the development of primals. Developmentalists can examine within-family concordance in primals between parents and children and can examine between-person within-families, between-families within-cultures, and between-culture sources of variance in primals. Evidence to date suggests that primals influence well-being. It is therefore critical to understand where primals come from, and the work and expertise of developmental scientists are critical to this endeavor.

This manuscript is a theoretical article that did not involve data collection. No human participants were involved, so approval was not required from an Ethics Committee.

The authors have no conflicts of interest to declare.

This research has been funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development grant RO1-HD054805 and the University of Pennsylvania and the Templeton Religion Trust (TRT0298). The funders had no role in the preparation of the manuscript.

Jennifer E. Lansford: conceptualization and writing – original draft preparation. Nicholas Kerry: conceptualization and writing – reviewing and editing. Suha M. Al-Hassan, Dario Bacchini, Marc H. Bornstein, Lei Chang, Kirby Deater-Deckard, Laura Di Giunta, Kenneth A. Dodge, Sevtap Gurdal, Daranee Junla, Paul Oburu, Concetta Pastorelli, W. Andrew Rothenberg, Ann T. Skinner, Emma Sorbring, Laurence Steinberg, Liliana Maria Uribe Tirado, Saengduean Yotanyamaneewong, and Liane P. Alampay: investigation and writing – reviewing and editing.

Data were not used in this theoretical article. Further inquiries can be directed to the corresponding author.