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Moral development focuses on the emergence, change, and understanding of morality from infancy through adulthood. In the field of moral development, morality is defined as principles for how individuals ought to treat one another, with respect to justice, others’ welfare, and rights. In order to investigate how individuals understand morality, it is essential to measure their beliefs, emotions, attitudes, and behaviors that contribute to moral understanding. The field of moral development studies the role of peers and parents in facilitating moral development, the role of conscience and values, socialization and cultural influences, empathy and altruism, and positive development. The interest in morality spans many disciplines (e.g., philosophy, economics, biology, and political science) and specializations within psychology (e.g., social, cognitive, and cultural). Moral developmental psychology research focuses on questions of origins and change in morality across the lifespan.
Introductory works/historical background 
The founder of psychoanalysis, Freud (1962), proposed the existence of a tension between the needs of society and the individual. According to Freud, moral development proceeds when the individual’s selfish desires are repressed and replaced by the values of important socializing agents in one’s life (for instance, one’s parents). A proponent of behaviorism, Skinner (1972) similarly focused on socialization as the primary force behind moral development. In contrast to Freud’s notion of a struggle between internal and external forces, Skinner focused on the power of external forces (reinforcement contingencies) to shape an individual’s development. While both Freud and Skinner focused on the external forces that bear on morality (parents in the case of Freud, and behavioral contingencies in the case of Skinner), Piaget (1965) focused on the individual’s construction, construal, and interpretation of morality from a social-cognitive and social-emotional perspective.
To understand adult morality, Piaget believed that it was necessary to study both how morality manifests in the child’s world as well as the factors that contribute to the emergence of central moral concepts such as welfare, justice, and rights. Interviewing children using the Clinical Interview Method, Piaget (1965) found that young children were focused on authority mandates, and that with age children become autonomous, evaluating actions from a set of independent principles of morality. Kohlberg (1963) expanded upon Piagetian notions of moral development. While they both viewed moral development as a result of a deliberate attempt to increase the coordination and integration of one’s orientation to the world, Kohlberg provided a systematic 3-level, 6-stage sequence reflecting changes in moral judgment throughout the lifespan. Specifically, Kohlberg argued that development proceeds from a selfish desire to avoid punishment (personal), to a concern for group functioning (societal), to a concern for the consistent application of universal ethical principles (moral).Although Kohlberg is praised for his work there have been many questions raised whether or not it is 100% accurate. Many people believe his 6 stage theory was sexist because only males were in the test group for this study.
Turiel (1983, 1998, 2002, 2006) argued for a social domain approach to social cognition, delineating how individuals differentiate moral (fairness, equality, justice), societal (conventions, group functioning, traditions), and psychological (personal, individual prerogative) concepts from early in development throughout the lifespan. Over the past 40 years, research findings have supported this model, demonstrating how children, adolescents, and adults differentiate moral rules from conventional rules, identify the personal domain as a nonregulated domain, and evaluate multifaceted (or complex) situations that involve more than one domain. This research has been conducted in a wide range of countries (Argentina, Australia, Brazil, Canada, China, Colombia, Germany, Hong Kong, India, Italy, Japan, Korea, Nigeria, Spain, Switzerland, Turkey, U.K., U.S., Virgin Islands) and with rural and urban children, for low and high income communities, and traditional and modern cultures. Turiel's social domain theory showed that children were actually younger in developing moral standards than past psychologists predicted.
For the past 20 years, researchers have expanded the field of moral development, applying moral judgment, reasoning, and emotion attribution to topics such as prejudice, aggression, theory of mind, emotions, empathy, peer relationships, and parent-child interactions. The Handbook of Moral Development (2006), edited by Melanie Killen and Judith Smetana, provides a wide range of information about these topics covered in moral development today.
Interpersonal influences on moral development 
Children’s interactions with caregivers and peers have been shown to influence their development of moral understanding and behavior. Researchers have addressed the influence of interpersonal interactions on children’s moral development from two primary perspectives: socialization/internalization (Grusec & Goodnow, 1994; Kochanska & Askan, 1995; Kochanska, Askan, & Koenig, 1995) and social domain theory (Turiel, 1983; Smetana 2006). Research from the social domain theory perspective focuses on how children actively distinguish moral from conventional behavior behavior based in part based on the responses of parents, teachers, and peers (Smetana, 1997). Adults tend to respond to children’s moral transgressions (e.g. hitting or stealing) by drawing the child’s attention to the effect of his or her action on others, and doing so consistently across various contexts. In contrast, adults are more likely to respond to children’s conventional misdeeds (e.g. wearing a hat in the classroom, eating spaghetti with fingers) by reminding children about specific rules and doing so only in certain contexts (e.g. at school but not at home) (Smetana, 1984; 1985). Peers respond mainly to moral but not conventional transgressions and demonstrate emotional distress (e.g. crying or yelling) when they are the victim of moral but not conventional transgressions (Smetana, 1984). Children then use these differing cues to help determine whether behaviors are morally or conventionally wrong.
Research from a socialization/internalization perspective focuses on the ways in which adults pass down standards of behavior to children through parenting techniques and why children do or do not internalize those values (Grusec & Goodnow, 1994; Kochanska & Askan, 1995). From this perspective, moral development involves children’s increasing compliance with and internalization of adult rules, requests, and standards of behavior. Using these definitions, researchers find that parenting behaviors vary in the extent to which they encourage children’s internalization of values, and that these effects depend partially on child attributes, such as age and temperament (Grusec & Goodnow, 1994). For instance, Kochanska (1997) showed that gentle parental discipline best promotes conscience development in temperamentally fearful children but that parental responsiveness and a mutually responsive parent-child orientation best promote conscience development in temperamentally fearless children. These parental influences exert their effects through multiple pathways, including increasing children’s experience of moral emotions (e.g. guilt, empathy) and their self-identification as moral individuals (Kochanska, 2010).
Morality and cognition: intentionality 
A hallmark of moral understanding is intentionality. Recent research on children’s theory of mind, ToM, has focused on when children understand others’ intentions (Wellman & Lui, 2004). The moral concept of actor intentionality develops with experience in the world. Yuill (1984) presented evidence that comprehension of actor intentions plays a role in moral judgment, even in young children. Killen, Mulvey, Richardson, Jampol, and Woodward (2011) present evidence that with developing false belief competence (ToM), children are capable of using information about actor intentions when making moral judgments about act acceptability and punishment acceptability, recognizing that accidental transgressors, who do not hold negative intentions, should not be held accountable for negative outcomes. In this study, children who lacked false belief competence were more likely to attribute blame to an accidental transgressor than children with demonstrated false belief competence. In addition to evidence from a social cognitive perspective, behavioral evidence suggests that even three-year-olds have the capacity to take into account actor intention and apply this information when responding to situations. Vaish, Carpenter, and Tomasello (2010), for instance, present evidence that three-year-olds are more willing to help a neutral or helpful actor than a harmful actor. Beyond the ability to identify actor intentionality, mental state understanding plays a crucial role in identifying victimization. While obvious distress cues (e.g. crying) allow even three year olds to identify victims of harm (Zelazo, Helwig, & Lau, 1996), it isn't until around six years of age that children are able to appreciate that a person may be an unwilling victim of harm even in the absence of obvious distress (Shaw & Wainryb, 2006). In their study, Shaw and Wainryb (2006) found that children older than six interpret compliance, resistance, and subversion to illegitimate requests (e.g., clean my locker) from the perspective of a victim. That is, they judge that victims who resist illegitimate requests will feel better than victims who comply.
Morality and intergroup attitudes 
Researchers interested in intergroup attitudes and behavior have approached the study of stereotypes, prejudice and discrimination in children and adolescents from several theoretical perspectives. Some of these theoretical frameworks include: Cognitive Development Theory (Aboud, 1988); Social Domain Theory (Killen & Rutland, 2011; Killen, Sinno, & Margie, 2007); Social Identity Development Theory (Nesdale, 1999); Developmental Intergroup Theory (Bigler & Liben, 2006); Subjective Group Dynamics (Abrams, Rutland, & Cameron, 2003; Rutland, Killen, & Abrams, 2010); Implicit Theories (Levy, Chiu, & Hong, 2006) and Intergroup-contact Theory (Pettigrew & Tropp, 2008). The plethora of research approaches is not surprising given the multitude of variables, (e.g. group identity, group status, group threat, group norms, intergroup contact, individual beliefs and context) that need to be considered when assessing children’s intergroup attitudes. While most of this research has investigated two-dimensional relationships between each of the three components: stereotypes, prejudice and discrimination (e.g., role of stereotypes in intergroup prejudice, use of stereotypes to reason about intergroup discrimination, how prejudices manifest into discrimination), very few have addressed all three aspects of intergroup attitudes and behaviors together (McKown, 2004).
In developmental intergroup research, stereotypes are defined as judgments made about an individual’s attributes based on group membership (Killen, Margie, & Sinno, 2006; Killen et al., 2007). Social psychologists focus on stereotypes as cognitive components influencing intergroup behaviors and tend to define them as being fixed concepts associated with a category (Allport, 1954). Prejudice, on the other hand is defined in terms of negative attitudes or affective expressions toward a whole group or members of a group (Stangor, 2009). Negative stereotypes and prejudices can manifest into discrimination towards an outgroup and for children and adolescents this may come in the form of exclusion from peer groups (Killen & Rutland, 2011).
Within an intergroup encounter children and adolescents have been found to weigh concerns about fairness, justice and the welfare of others when making decisions about inclusion or exclusion of an outgroup member into a peer group.
Intergroup exclusion context provides an appropriate platform to investigate the interplay of these three dimensions of intergroup attitudes and behaviors, prejudice, stereotypes and discrimination. Developmental scientists working from a Social Domain Theory (SDT: Killen et al., 2006; Smetana, 2006) perspective have focused on methods that measure children’s reasoning about exclusion scenarios. This approach has been helpful in distinguishing which concerns children attend to when presented with a situation in which exclusion occurs. Exclusion from a peer group could raise concerns about moral issues (e.g. fairness and empathy towards excluded), social-conventional issues (e.g., traditions and social norms set by institutions and groups) and personal issues (e.g., autonomy, individual preferences related to friendships), and these can coexist depending on the context in which the exclusion occurs. In intergroup as well as intragroup contexts, children need to draw on knowledge and attitudes related to their own social identities, other social categories, the social norms associated with these categories as well as moral principals about the welfare of the excluded, and fair treatment, to make judgments about social exclusion.
Findings from a Social Domain Theory perspective show that children are sensitive to the context of exclusion and pay attention to different variables when judging or evaluating exclusion. These variables include, social categories, the stereotypes associated with them, children’s qualifications as defined by prior experience with an activity, personality and behavioral traits that might be disruptive for group functioning and conformity to conventions as defined by group identity or social consensus. In the absence of information, stereotypes can be used to justify exclusion of a member of an out-group (Horn 2003, Killen and Stangor, 2001). One’s personality traits and whether he/she conforms to socially accepted behaviors related to identity also provide further criteria for social acceptance and inclusion by peers (Killen, Crystal, & Watanabe, 2002; Park, Killen, Crystal, & Watanabe, 2003). As children get older they become more attuned to issues of group functioning and conventions and weigh them in congruence with issues of fairness and morality (Killen & Stangor, 2001).
Moral emotions 
Moral questions tend to be emotionally charged issues which evoke strong affective responses. Consequently, emotions likely play an important role in moral development. However, there is currently little consensus among theorists on how emotions influence moral development. Psychoanalytic theory, founded by Freud, emphasizes the role of guilt in repressing primal drives. Research on prosocial behavior has focused on how emotions motivate individuals to engage in moral or altruistic acts. Social-cognitive development theories have recently begun to examine how emotions influence moral judgments. Intuitionist theorists assert that moral judgments can be reduced to immediate, instinctive emotional responses elicited by moral dilemmas.
Research on socioemotional development and prosocial development has identified several "moral emotions" which are believed to motivate moral behavior and influence moral development (Eisenberg, 2000 for a review). The primary emotions consistently linked with moral development are guilt, shame, empathy, and sympathy. Guilt has been defined as "an agitation-based emotion or painful feeling of regret that is aroused when the actor actually causes, anticipates causing, or is associated with an aversive event" (Fergusen & Stegge, 1998). Shame is often used synonymously with guilt, but implies a more passive and dejected response to a perceived wrong. Guilt and shame are considered "self-conscious" emotions, because they are of primary importance to an individual’s self-evaluation. In contrast to guilt and shame, empathy and sympathy are considered other-oriented moral emotions. Empathy is commonly defined as an affective response produced by the apprehension or comprehension of another’s emotional state which mirrors the other’s affective state. Similarly, sympathy is defined as an emotional response produced by the apprehension or comprehension of another’s emotional state which does not mirror the other’s affect, but instead causes one to express concern or sorrow for the other (Eisenberg, 2000).
The relation between moral action and moral emotions has been extensively researched. Very young children have been found to express feelings of care, and empathy towards others, showing concerns for other’s well being (Eisenberg, Spinard, & Sadovsky, 2006). Research has consistently demonstrated that when empathy is induced in an individual, he or she is more likely to engage in subsequent prosocial behavior (Batson 1998; Eisenberg, 200 for review). Additionally, other research has examined emotions of shame and guilt in relation to children’s emphatic and prosocial behavior (Zahn-Waxler & Robinson, 1995).
While emotions serve as information for children in their interpretations about moral consequences of acts, the role of emotions in children’s moral judgments has only recently been investigated. Some approaches to studying emotions in moral judgments come from the perspective that emotions are automatic intuitions that define morality (Greene, 2001; Haidt, 2001). Other approaches place emphasis on the role of emotions as evaluative feedback that help children interpret acts and consequences (Turiel & Killen, 2010). Research has shown children attribute different emotional outcomes to actors involved in moral transgressions than those involved in conventional transgressions (Arsenio, 1988, Arsenio & Fleiss, 1996). Emotions may help individuals prioritize among different information and possibilities and reduce information processing demands in order to narrow the scope of the reasoning process (Lemerise & Arsenio, 2000). In addition, Malti, Gummerum, Keller, & Buchmann, (2009) found individual differences in how children attribute emotions to victims and victimizers.
Morality and culture 
The role of culture on moral development is an important topic which raises fundamental questions about what is universal and what is culturally specific regarding morality and moral development. Many research traditions have examined this question, with social-cognitive and structural developmental positions theorizing that morality has a universal requirement to it, drawing from moral philosophy. The expectation is that if morality exists, it has to do with those values that are generalizable across groups and cultures. Alternatively, cultural relativistic positions have been put forth mostly by socialization theories which focus on how cultures transmit values rather than what values are applied across groups and individuals.
As an example of some of the debates, Shweder, Mahapatra, and Miller (1987) argued for moral relativism, or the notion that different cultures defined the boundaries of morality differently. In contrast, Turiel and Perkins (2004) argued for the universality of morality, focusing largely on evidence throughout history of resistance movements that fight for justice through the affirmation of individual self-determination rights. In an update on the debate between moral relativism and moral universality, Miller (2006) provides a thoughtful review of the cultural variability of moral priorities, arguing that rather than variability in what individuals consider moral (fairness, justice, rights), there is cultural variability in the priority given to moral considerations (e.g., the importance of prosocial helping). Wainryb (2006), in contrast, reviews extensive literature which has demonstrated that children in diverse cultures such as the U.S., India, China, Turkey, and Brazil share a pervasive view about upholding fairness and the wrongfulness of inflicting harm on others. Cultures vary in terms of conventions and customs, but not principles of fairness, which appear to emerge very early in development, prior to socialization influences. Wainryb (1991; 1993) shows that many apparent cultural differences in moral judgments are actually due to different informational assumptions, or beliefs about the way the world works. When people hold different beliefs about the effects of actions or the status of different groups of people, their judgments about the harmfulness or fairness of behaviors often differ, even when they are applying the same moral principles.
Another powerful socializing mechanism by which values are transmitted is religion, which is for many inextricably linked to a cultural identity. Nucci and Turiel (1993) assessed individuals’ reactions to dictates from God, and the distinctions in their reactions to God’s moral (e.g., stealing) and conventional (e.g., day of worship) dictates. One explicit manner in which societies can socialize individuals is through moral education. Solomon and colleagues (1988) present evidence from a study that integrated both direct instruction and guided reflection approaches to moral development, with evidence for resultant increases in spontaneous prosocial behavior. Finally, studies of moral development and cultural issues cover many subtopics. For instance, a recent review of studies examining social exclusion, identifies cultural similarities in the evaluation of exclusion across a range of societies and cultures (Hitti, Mulvey & Killen, 2011).
The role of religion in a culture can have a large impact on a child's moral development, and sense of moral identity. Intrinsic aspects of religion have a positive impact on the internalization of moral identity and the symbolism of moral identity. Religiosity is a strong precursor of moral identity. Religion also is a family activity in a childs life which helps the child internalize the parents morals. Family participation in religious organizations during early and middle childhood are predictive of better emotional health and fewer negative behaviors during middle childhood.
Morality and the allocation of resources 
The notion of justice implies an impartial weighing of individual’s needs. Early research focused on the contingency between conceptions of justice and Piagetian logical operations (Damon, 1975). In the realm or society and law, Helwig and Jasiobedzka (2001) asked adolescents to judge the acceptability of beneficial (e.g., a traffic law) and unjust laws (e.g., denial of education to a group of individuals). Park and Killen (2010) extended the notion of individuals’ needs to include the needs of groups. In their study, they asked children to consider group members’ desires (exclusion) that contrasted with an individual’s desires (inclusion) in an exclusion scenario. The results demonstrated that children viewed exclusion based on personality as less wrong than exclusion based on group membership, such as gender and nationality. Studies have also been conducted on reactions to injustice. Astor (1994) for instance, studied the reactions of violent and nonviolent individuals to provoked and unprovoked violent behavior. In the provocation condition, violent, as opposed to nonviolent, children were more likely to focus on retribution as a means of restoring justice to the situation. Other research has focused on evaluating the universality of development of notions of distributive justice. Enright, Enright, and Lapsley (1981) for instance, found that middle-SES children focused more on individuals’ needs when determining resource allocation in hypothetical scenarios than did low-SES children. Research within behavioral economics (Fehr et al., 2008, Almas et al., 2010), indicates that even very young children strongly adhere to concepts of fairness and justice when distributing resources, with children moving from a focus on strict equality to a more nuanced sense of justice based on merit, with age.
Moral neuroscience 
The advent and development of imaging technologies allows for an increasingly precise analysis of the neural bases of moral judgment, emotion, and behavior, allowing for both a structural and functional view of the organ that organizes what we perceive in the world and directs how we respond to that world. For instance, Blair (2007) has documented cortical regions that are differentially active when considering emotional expressions (e.g., fear) in neurotypical controls compared to participants with antisocial personality disorder. Decety and Michalska (2009) have identified neural circuits underlying empathic and sympathetic reactions to others’ pain. In another fMRI study, one hundred and twenty-six participants aged between 4 and 37 years viewed scenarios depicting intentional versus accidental actions that caused harm/damage to people and objects. Morally, salient scenarios evoked stronger empathic sadness in young participants and were associated with enhanced activity in the amygdala, insula, and temporal poles. While intentional harm was evaluated as equally wrong across all participants, ratings of deserved punishments and malevolent intent gradually became more differentiated with age. Furthermore, age-related increase in activity was detected in the ventromedial prefrontal cortex in response to intentional harm to people, as well as increased functional connectivity between this region and the amygdala. This study provides evidence that moral reasoning involves a complex integration between affective and cognitive processes that gradually changes with age, and supports the view that negative emotion alerts the individual to the moral salience of a situation by bringing discomfort and thus can serve as an antecedent to moral judgment. Varying the description of the trustworthiness of a partner in an economic decision game, Delgado, Frank, and Phelps (2005) were able to show that neural regions associated with reward processing were affected by the extent to which the participant thought she could trust the partner.
Morality and Society 
The social domain theory had drawn the idea that there was a connection between the child's developing concepts of morality, and other domains of social knowledge, such as social convention. In a few tests Turiel had asked his test groups if they would hit their friend. They all said no because they would get in trouble. He then offered the idea that if they wouldn't get in trouble would they do it and most said no because they knew the other person would get hurt and that would be wrong. This test showed that society creates standards for us and teaches us the right and wrong from interactions with other people and how they follow societal rules.
Morality Effect on Adaptability 
The development and internalization of morals at an early age has been shown to be predictive of future adaptive skills and future socialization skills. A study that tested children at 25, 38, and 52 months on internalization of their mothers and fathers rules, and the children's perception of their morals found that the children were more competent and better socialized if they were highly developed in the two areas tested. The relation between the child's history of empathy toward the mother and future socialization was also significant. Children who are empathic at a young age also, will find it easier to maintain relationship, both romantically and with friends and co-workers. This skill is extremely important in communicating with people and being able to understand others perspective. Children who have high internalization of the mother and father's rules are also more likely to perceive themselves being more moral later in childhood.
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