Kindness in Children and Adolescents: Conceptualization and Interventions

Definition

Kindness, from the perspective of positive psychology and character strengths, is a virtue that supports others’ emotional and practical needs, strengthens relationships, and fosters a positive, inclusive social environment. Kindness can be defined as characterized by a set of behaviors, attitudes, and dispositions rooted in care, empathy, respect, and prosocial motivation. Kindness is a multidimensional, prosocial construct that developmentally evolves, shaped by cognitive development, personal and interpersonal factors, and social contexts. As individuals mature across childhood and adolescence, their understanding and expression of kindness become more complex, reflecting growing social and relational awareness and competency.

1. Introduction

There are divergent perspectives on how to conceptualize kindness in the existing literature, as well as a lack of conceptual clarity and theoretical integration. This entry paper centers on the conceptual framework of positive psychology, within which kindness is considered a psychological strength in a prosocial relational context. According to the Values in Action (VIA) model [1], kindness is within the virtue of humanity and is among the “interpersonal strengths that involve tending and befriending others” (cited in [2], p. 25). Within this framework, kindness can be studied as a trait, as a stable personal characteristic, or a state, manifested as a momentary reaction, or a behavior/skill, which can be acquired or cultivated in supportive environments. Also, kindness is not a singular construct but a multifaceted concept that includes three core components: kind emotions, kind cognitions, and kind behaviors [3].

By taking a developmental lens, the importance of recognizing and fostering kindness in developmentally sensitive periods, such as childhood and adolescence, is emphasized in this paper. Early studies in developmental psychology focused on prosocial behavior and altruism in children, laying the groundwork for understanding kindness as a distinct construct. Kindness emerges early in childhood, with prosocial behaviors observed in infants as young as 14 months of age [4,5]. The capacity for kindness increases with age, becoming more sophisticated and intentional throughout childhood and adolescence [6,7]. Studies have consistently shown that engaging in acts of kindness, such as prosocial behavior, is associated with healthy development, especially enhanced social connections and well-being in both children and adults [8,9,10]. Given the benefits of kindness, research has examined interventions of kindness in various settings, such as schools, clinics, and workplaces, offering evidence-based strategies for promoting kindness. In this entry paper, we focus on kindness in school contexts and kindness interventions for school-age populations. Also, though most kindness research has been conducted in North American contexts, some studies were conducted in diverse regions or cultural contexts. Findings that expand the understanding of kindness’s conceptualization and its implications in promoting kindness in children and adolescents are incorporated.

1.1. Kindness Perceptions in School Contexts

Besides academic definitions of kindness, we ask, what is kindness in the eyes of people in daily life? Within the school context, several studies have analyzed students’ and teachers’ viewpoints (e.g., [11,12,13,14,15]) and a few studies from diverse cultural settings (e.g., [16]) emerged to reveal both universal themes and culturally specific understandings of kindness.

1.1.1. Students’ Perspective

Prior research has shown that preschoolers and elementary-age children enact kindness through behaviors, such as sharing, helping, and offering comfort [6]. Research on children’s subjective views of kindness is rare, but a few studies have shown an initial understanding. For example, in a study with early elementary students in Canada (N = 112, ages 5–8) [11], researchers asked students to draw what kindness looked like and kind acts they had performed at school recently. Comparable findings were found in a larger replication study that also asked the children to draw kindness at school (N = 652, kindergarten to third-grade students, age 5.25–9.33) [12]. The drawings showed that children viewed kindness as (1) physically helping others (e.g., “My friend fell down and I helped her get up.”); (2) giving to others (e.g., “We’re not fighting and I asked ‘Do you want a flower?’”); (3) maintaining friendships (e.g., “I’m passing the ball so he can play 4-Square.”); and (4) helping others emotionally (e.g., “Dylan’s feeling sad. I’m asking, ‘Are you okay?’”).

Another study focused on older school-age children in Canada (N = 1752, fourth to eighth graders, age 9–14 years and 9 months) and collected handwritten responses to open-ended questions on kindness in a survey [13]. Predominant responses suggested three themes for perceived kindness, including helping (32.7%), showing respect (24.3%), and encouraging/advocating (10.8%). The majority of kindness examples reflected the theme of helping, categorizing them into helping physically (61.8%, e.g., “I helped a person when they were hurt falling from the playground”), academically (23%, e.g., “help others who struggle to complete other schoolwork”), and emotionally (15.2%, e.g., “I helped my brother when he was crying”). Examples of showing respect include taking turns, having manners, using the “Golden Rule” (treating others as one would want to be treated by themselves), being responsible, holding the door for someone, not being rude, and not swearing. Moreover, examples of encouraging/advocating include comments to make people feel good, complimenting, and standing up for someone who is being bullied [13]. A few other simple, less explicit behaviors, such as listening to others, being careful with words, and not bullying others, are also considered to be kind [13].

Compared to younger children (ages 5–8 years) [11], older children (ages 9 years–14 years and 9 months) in Binfet and Passmore’s study [13] were more likely to show respect as an example of kindness. Moreover, accepting/understanding, encouraging/advocating, happiness, and honesty are new themes that emerged in this sample [13], which were not identified in the younger sample [11]. Additionally, helping with academic work and giving time to others emerged as new subthemes in older children [13], compared with helping emotionally, helping physically, and giving objects, as expressed by younger children [11]. It is noteworthy that one self-oriented kindness theme emerged in the older sample: happiness (being happy, having a positive attitude, and being confident) [13], which corresponds with the other-oriented kindness theme of emotional help (e.g., making someone feel happy). The themes of accepting/understanding others (being open to the differences in others, being open to others’ beliefs, and perspective-taking) and honesty (trustworthiness, keeping secrets, loyalty, playing by the rules, being kind without trying, and being fair) show that older children have more developed cognitions such as perspective-taking [3].

Binfet and Passmore’s study [13] also asked students’ perceived adult agents of kindness who most frequently enact kindness, and results showed that more than half of students (55%) reported teachers, followed by the principal/vice-principal (16.9%), and librarians (11.8%). Some students think that the very act of teaching means kindness. Moreover, many students indicated that teachers and principals’ jobs should go beyond just teaching or administration, but also foster a culture of kindness in school, such as keeping everyone happy, safe, and nice to others. Most students (55%) consider the classroom as the main location of kindness, followed by outside/playground (22.44%).

Another study applied different research methods with adolescents that helped them understand their view of kindness. Specifically, Cotney and Banerjee [14] conducted six semi-structured focus groups (three to eight students in each group, 45–60 min) with 32 UK adolescents (age 11–15) on adolescents’ conceptualization of kindness. They identified emotional support, social inclusion, helping, honesty, positive sociality, complimenting, and generosity as examples of kind acts, which are similar to the themes mentioned previously. They also identified different themes from Binfet and Gaertner’s [11] and Binfet and Passmore’s study [13], both of which used individual self-report methods by either asking participants to draw or answer open-ended questions in surveys. The different themes include proactive support (providing support for others when they are not experiencing emotional upset), expressing forgiveness (explicitly forgiving others’ transgressions and/or mistakes), and formal kindness (a premeditated act of kindness, often collective, involving more than one individual, such as fundraising for charity or volunteering). These expanded themes suggest increased complexity in adolescents’ understanding of abstract concepts, such as kindness, likely due to advanced cognitive ability and richer interactions between the individual and the context (e.g., life experiences, peer relationships).

Building on previous developmental findings, Binfet et al. [15] extended the inquiry into how high school students conceptualize and enact kindness within school contexts (N = 479, Mage = 16.2). Using a mixed-methods approach combining self- and other-ratings with open-ended questions, researchers found that students most frequently defined kindness as helping, giving, and showing care and concern for others, paralleling themes observed in younger samples of elementary and middle school students [13]. Quantitatively, girls reported higher self-rated kindness levels than boys, and students rated themselves as kinder in face-to-face than online interactions. Notably, students in 12th grade viewed both themselves and their schools as kinder compared to younger peers. Qualitative findings showed that students’ meaningful acts of kindness were largely reactive (spontaneous responses to others’ needs) and that peers were perceived as the strongest influence on one’s kindness, followed by teachers and classmates. These findings suggest that by adolescence, students hold a sophisticated, relational view of kindness grounded in empathy, self-awareness, and social connection, and that the school environment continues to play a key role in shaping these prosocial orientations [15].

To this date, research examining kindness perceptions in K-12 school contexts across diverse cultures remains limited, while a few studies with young adult samples provide valuable insights into cultural variations in kindness conceptualization, including both similarities and meaningful differences. For instance, Gherghel and Hashimoto [16] explored how university students (N = 58, mean age = 19.29) in Japan construed kindness through a three-week intervention study. Content analysis of participants’ descriptions of kind acts revealed categories similar to Western samples [11,12,13,14], including instrumental support (e.g., offering things, helping with work or school, doing something in someone’s place), emotional support (e.g., counseling and encouragement), and informational support (e.g., teaching, giving directions). The most frequently mentioned acts fell in the instrumental support category (69.5% of examples), with the most common acts as “doing something in someone else’s place” (12.6%) and “help with work or school” (11.4%). Notably, while emotional support represented 21.6% of kindness examples, Japanese participants did not frame spending time together as kindness, as this behavior is more readily associated with gratitude expression in their culture. It seems companionship or mutual benefit, despite the components of positive social interaction, may not be conceptualized as kindness by Japanese young adults, which is in contrast to Western samples where themes related to social connection, such as maintaining friendships [11], giving time to others [13], and social inclusion [14], were identified as forms of kindness. These findings suggested that the role of cultural values may shape how kindness is conceptualized and enacted.

Furthermore, Cotney and Banerjee [14] studied the antecedents of kindness from the perspective of students, including situational triggers and psychological goals. Situational triggers include emotional, instrumental, and health-related needs of others, personal life events, and one’s own emotions. Psychological goals include other-focused, self-focused, and relationship-focused, and non-autonomous goals [14]. The situational triggers of personal life events and one’s own emotions might indicate the importance of self-kindness, as the participants’ situations in which positive (or neutral) life events and positive mood trigger kind acts, though emotional triggers can include guilt and gratitude [14]. Some discussions also implied that certain aspects of emotional well-being may be required for the giver to fully engage with kindness [14]. Specifically, in this study, some participants indicated that confidence is often required to perform kind acts, as approaching others to express kindness can be challenging; others noted that individuals experiencing low mood may find it difficult to be kind, as they tend to focus on their own distress rather than attending to others [14]. Self-transcendent values (caring for people and entities outside of oneself) are also positively associated with kind behaviors [17] and numerous aspects of well-being, such as hope, purpose in life, and affect balance [18].

Additionally, Cotney and Banerjee’s study [14] revealed factors that can influence how kindness is enacted, intended, or received from the students’ perspective. Empathy is highly relevant in being kind, while the participants also pointed out that beyond feeling empathic to others and willingness to help, social context, such as aspects of the dyadic relationship (between the giver and receiver of kindness), particularly the level of relatedness and the relationship history, are highly influential in individuals’ reluctance in acts of kindness [14]. For instance, a negative experience in the past, such as bullying, could make a student feel “strange” about being kind to others, and being kind to strangers when no one expected it could induce some emotional burden for the giver. Also, some participants noted it is often inappropriate to approach strangers and sometimes it is uncertain how the recipient would evaluate the act of kindness (e.g., the giver thinks the act is being kind, but the recipient may not) [14]. Thus, the giver’s life experiences and ability to assess others’ needs and anticipate their reactions also contribute to the occurrence or lack of kindness [14]. Importantly, being aware of how students of different age groups may conceptualize kindness differently is especially important for designing kindness interventions, as Binfet and Gaertner [11] pointed out that small gestures considered as kindness by young children (such as “following directions” and “wearing a smile”) may be given less emphasis by adults, who may consider those small gestures not significant enough to be counted as kindness [14].

Another trend identified in perceived kindness is that students in higher grades tend to perceive less kindness in school [12,19,20], which is aligned with the declines in students’ perceptions of other key positive school climate constructs, such as student autonomy and the clarity and consistency of school rules [21]. Prior research also found that girls enact more kind behaviors than boys [20,22], although this might vary depending on the age and prosocial behavior measurement [12]. In addition, a few studies have found that females have stronger character strengths, such as kindness and love, than males [23,24,25].

1.1.2. Teachers’ Perspectives

Frequent interpersonal interactions take place in school contexts where teachers are prosocial behavioral models for the students. Therefore, understanding how they conceptualize and enact kindness in the school context is important [26]. Based on a study conducted with teachers of elementary, middle, and high schools in western Canadian cities [26], five major themes of kindness were perceived by teachers in schools: (1) caring (25%, “caring for the people around you and wanting good things for them”); (2) perspective taking/showing empathy (15%, “striving to understand the feelings and emotional states of others, and doing whatever they need”); (3) being respectful (15%, “showing respect to self and to others through actions that reveal acceptance of individual differences”); (4) helping (11%, “doing things for someone else without being concerned about how it benefits you”); and (5) encouraging (11%, “making others feel good about themselves or their accomplishments”).

These themes align with Eisenberg et al.’s [22] definition of kindness: helping, sharing, comforting, and cooperating. Examples of kindness raised by the teachers also mirror their perceptions of kindness in students, such as giving another teacher a ride home (helping), making dinner for a low-income student (giving), thinking of people around (caring), giving an important task to a student with low self-esteem (encouraging), and thanking others for helping out the running club (acknowledging) [26]. In addition, teachers reported that the classroom was the location of kindness most often (81%), followed by “everywhere throughout the school” (7%) [26].

Similar themes emerged in a Greek study [27] of pre-service early childhood teachers (N = 219, ages 19–20). Teachers identified kindness primarily as respect for others (64.8%), help and caring (20.54%), and understanding (15.06%). They distinguished between formal kindness (socially accepted “good manners,” 38.81%) and authentic acts of kindness (genuine actions “from the heart,” 52.05%), with 11.41% emphasizing that kindness is foundational to teaching practice. These findings reinforce the themes from Canadian studies while highlighting cultural nuances in how kindness authenticity is conceptualized.

1.1.3. Summary of Research on Kindness Perceptions in School Contexts

Though with a small number of studies, the findings collectively showed an evolving understanding and enactment of kindness across developmental stages within school contexts. Specifically, young children primarily express kindness through concrete behaviors such as sharing, helping physically, giving, and offering emotional support, often conceptualized through drawings and self-reports in early childhood research. As children mature into late childhood and adolescence, their conceptualization of kindness broadens and becomes more nuanced, incorporating themes such as respect, encouragement, honesty, social inclusion, proactive support, forgiveness, and formalized acts like volunteering. These changes reflect developmental progression, especially in social cognition, such as social awareness and perspective-taking. Beyond the cognitive factors, relational and contextual factors become more important in adolescence, especially in high school contexts. The interplay between intrapersonal factors (e.g., empathy, self-awareness, confidence, emotional well-being), the influence of peers and school adults, as well as the dyadic relationship between giver and receiver, together affect students’ decision or capacity to engage in kindness, especially overt prosocial behavior toward others.

Taken together, research across Western, East Asian, and Mediterranean contexts shows that both teachers and students view kindness as a multidimensional construct consisting of helping, giving, encouraging, and respecting others. While core themes remain consistent, cultural nuances appear in how kindness is framed (formal vs. authentic in Greek contexts) and which behaviors are recognized as kind (e.g., companionship is rarely framed as kindness by Japanese participants, even though it involves positive social interaction). These patterns suggest that what counts as kindness and how it is enacted may vary across cultures. Students may emphasize kindness more in peer relationships than with teachers. Both teachers and students identify classrooms as key sites of kindness, where teachers and students interact every day. Adults in the school environment, particularly teachers and principals, are perceived by students as key agents of kindness, and the classroom is seen as the primary setting for kind acts. Overall, these findings underscore kindness as a multifaceted construct that develops in complexity with age, is deeply embedded in social relationships and contexts, and is influenced by both individual psychological factors and broader school climate dynamics. Therefore, embedding kindness in classrooms as an educational practice is essential for creating a learning environment for developing prosocial behaviors among students. Importantly, being aware of how students of different age groups and teachers may conceptualize kindness differently is especially important for designing kindness interventions, as Binfet and Gaertner [11] pointed out that small gestures considered as kindness by young children (such as “following directions” and “wearing a smile”) may be given less emphasis by adults, who may consider those small gestures not significant enough to be counted as kindness [14].

1.2. Kindness and Well-Being in the School Contexts

1.2.1. Research Findings

Guided by the positive psychology framework, kindness as a core character strength contributes to optimal human functioning. According to Seligman’s PERMA model [28], which refers to five core elements of well-being (i.e., Positive emotions, Engagement, Relationships, Meaning, and Accomplishment), acts of kindness theoretically would either represent or lead to positive emotions, engagement, and relationships, and kindness activities can foster a sense of purpose and self-efficacy or agency. Existing research on kindness in schools has provided evidence for some of these theoretical links. For example, kind acts demonstrated by teachers not only model kind behaviors but also positively impact teacher-student relationships [29,30]. Research from North America and Europe has shown that positive teacher-student relationships are linked to fewer anti-social behaviors in the U.S. and UK [31,32], whereas negative teacher-student relationships are linked to fewer prosocial behaviors in U.S. samples [33]. Furthermore, students’ perceptions of kindness in school also matter because it is part of the “construct of school climate” ([34], p. 115), which is associated with other positive perceived school contexts, including teacher support, peer support, classroom supportiveness, prosocial goals, social responsibility goals [12], and sense of school belonging [35]. Cross-cultural research supports these relationships: in Turkey, primary school students’ (N = 159, grades 3–4) perceptions of school kindness were significantly positively correlated with school attachment across all dimensions [36], and in Norway, a qualitative study with vulnerable upper secondary students (N = 17, mean age = 17.9) revealed that teacher kindness, expressed through smiling, showing care, being available for conversation, and making small practical adjustments, served as a protective factor. In interviews, one at-risk student noted, “You notice that there is something positive about going to school” when teachers demonstrate kindness [37].

The relations between kindness and well-being in schools were mostly studied through the measurement of prosocial behaviors. In addition to short- and long-term instrumental, physical health-related, and emotional benefits for the receiver [14], in particular, prosocial behavior is positively associated with later peer acceptance for the giver [38,39], which may in turn make children more likely to present prosocial behaviors [40]. Increasing peer acceptance is critical because it is associated with various academic [41] and social [42] outcomes, including a lower likelihood of being bullied [43].

The bidirectional influence between kindness and well-being has also been recognized in the literature. Studies primarily from North America have shown that happy people do good for others, and the prosocial behaviors they engage in increase their own well-being, which is indicated by life satisfaction, positive affect, happiness, and optimism [39,44]. This reciprocal relationship has been demonstrated cross-culturally. In Japan, Otake et al. [45] found that university students who counted their acts of kindness for one week showed significant increases in subjective happiness. Students who became happier performed significantly more acts of kindness and felt more gratitude, suggesting an upward spiral between kindness and happiness. For children, happy, well-liked youths tend to exhibit more inclusive behaviors and fewer externalizing behaviors [40], supporting the importance of happiness in fostering prosociality in children and a kindness culture from the younger generation in the communities at large. The reciprocal relationships between kindness and well-being also highlight the importance of self-kindness, as self-compassion (treating oneself with care and understanding) supports well-being [46], which in turn enables sustained kindness toward others [14].

Cultural context shapes how kindness relates to well-being. Shin et al. [47] conducted a cross-cultural comparison with U.S. (N = 280) and South Korean (N = 273) university students, finding that university students (N = 280) in the U.S. who read that kindness was “good for oneself” showed greater well-being improvements than controls, while students in South Korea who read kindness was “good for others” showed no additional benefit, possibly because such benefits are already culturally obvious in collectivist contexts [48,49]. This finding demonstrates that cultural context shapes how kindness framing influences well-being outcomes, suggesting that kindness interventions should be culturally adapted to align with students’ notions of self-construal.

1.2.2. Summary of Research on Kindness in Schools and Integration with the PERMA Model

Research on prosocial behavior—the primary operationalization of kindness in schools—shows that it benefits both recipients and givers. For the giver, prosocial actions increase peer acceptance, which further enhances social connection (Relationships) and contributes indirectly to students’ academic and social success (Accomplishment) [14,38,39,41,42]. Higher peer acceptance also reduces the likelihood of being bullied, illustrating how kindness-related processes create upward spirals of well-being within peer networks [42,43]. When teachers model kindness, they help build warm teacher–student relationships [29,30] and the relational protective factors, especially for at-risk students [36,37]—aligned with the Relationships component of PERMA—which in turn reduces antisocial behavior and promotes prosocial behavior among students [31,32,33]. Likewise, students’ perceptions of kindness contribute to a positive school climate associated with supportive classroom environments, prosocial and social-responsibility goals, and a stronger sense of school belonging, all of which reflect the relational and meaning-oriented dimensions of PERMA [34,35,36]. Some findings also resonate with broader evidence showing a bidirectional relationship between kindness and well-being, consistent with PERMA’s emphasis on reciprocal pathways to flourishing. That is, happier individuals engage in more prosocial behavior, and prosocial behavior in turn increases life satisfaction, positive affect, and optimism (Positive Emotions) [39,44]. Together, these interconnected findings provide evidence on how kindness may activate multiple PERMA pathways at once and underscore the importance of fostering both kindness toward others and self-kindness to sustain well-being in schools.

2. Kindness Interventions for Children and Adolescents

Positive Psychology Interventions (PPIs) have been important venues to enhance the value of well-being in positive psychology. There has been increased scholarly interest in creating and empirically evaluating interventions that foster kindness and prosocial behavior in children and adolescents. These other-oriented kindness interventions include classroom-wide school-based interventions, mindfulness programs delivered in clinical settings, and parent-mediated interventions, all of which demonstrate empirical support and can be delivered to individuals of various ages (e.g., [50,51,52,53,54,55,56,57]). Kindness-focused interventions targeting children and adolescents in two settings are presented below. While the large majority of existing empirical research on kindness interventions has been conducted in Western cultures, several recent studies have emerged from Asian contexts that highlight the efficacy of several interventions in promoting kindness in youth in Eastern cultures.

2.1. School-Based Interventions

School-based kindness interventions are uniquely positioned to decrease inequities in service delivery and offer children high-quality, evidence-based programming that increases prosocial interactions and other-oriented empathy without the financial burdens often associated with services provided in clinical settings. The gold-standard school-based kindness intervention for preschool-age children is a Mindfulness-Based Kindness Curriculum (MBKC), a 12-week program that integrates mindfulness and prosocial skills training to improve focused attention, self-regulation, and other-oriented kindness practices (e.g., empathy, sharing) [50]. The curriculum integrates developmentally appropriate music, stories, and physical exercise to teach core concepts in a digestible manner and is delivered twice weekly for approximately 20–30 min by a trained instructor [50]. Results from a randomized control trial indicate that preschoolers who completed MBKC demonstrated increased social competence and superior grades on the social-emotional development report card compared with their peers in a control group [50]. Moreover, this intervention was found to be effective at improving prosocial behaviors (e.g., sharing), executive functioning, cognitive empathy, and academic skills in ethnically diverse and economically disadvantaged preschoolers [51]. Emerging evidence also indicates that school-based interventions with a focus on compassion and caring are efficacious in non-Western educational contexts. For example, a large multi-site evaluation across 25 public elementary schools in eastern China found that a humane education program, with the core intervention elements as didactics and activities related to being compassionate and caring towards nature and animals, improved first- and second-grade students’ prosocial behavior [52].

Another type of school-based kindness intervention designed for adolescents focuses instead on promoting and tracking students’ prosocial or kind acts, including providing help to peers (e.g., with chores), demonstrating respect, complimenting or encouraging peers, and providing peers with money or other items [53]. In this intervention, students complete a booklet for four consecutive weeks, where they plan three weekly kind acts and reflect on these acts after they are completed. The results indicate that there was significant variability in adolescents’ engagement in the intervention, and the engagement levels were associated with the outcomes. In other words, students who demonstrated increased participation in the intervention demonstrated the most benefits (i.e., reducing negative effects and increasing self-perception as being a kind individual). Importantly, students primarily directed their kind acts to known peers rather than unknown peers, indicating that school-based interventions for adolescents promote existing social relationships rather than fostering prosocial interactions with those outside of one’s social network [53]. Binfet and Whitehead’s [53] study showed the promise of kindness-tracking interventions in improving adolescents’ well-being and existing social relationships. However, additional studies are needed to replicate and confirm these effects.

2.2. Community and Clinical Mindfulness-Based Interventions

The concept of mindfulness is used not only in the context of school-based kindness interventions but also in clinical or community settings. It reliably proves to be a powerful intervention component that teaches children how to be nonjudgmental and notice their thoughts, control impulses, and understand and regulate emotions. Although these interventions vary in duration and specific format, they all incorporate the core component of loving-kindness or compassion, in which the individual is prompted to form unconditional kind beliefs and attitudes about themselves and others, along with the desire to reduce others’ suffering or pain through positive intentions [54,55].

The briefest format of Loving-Kindness Meditation (LKM) is designed to be implemented for just seven minutes; the individual (i.e., a young adult) imagines sending love to loved ones, followed by sending love, health, and well-wishes through a series of phrases to a neutral stranger. The results indicate that this intervention improves both implicit and explicit positivity toward neutral strangers, along with implicit positivity toward oneself [56]. Several longer versions of LKM have also been developed, including a 7-week LKM training in which participants engaged in six one-hour-long group sessions led by a stress-management specialist [57]. Participants engaged in meditations in which they directed love and kindness toward themselves, loved ones, acquaintances, strangers, and all living beings, respectively. Sessions also integrated didactics that educated participants about the value of meditation and how to apply the teachings of sessions in their day-to-day lives; at-home LKM was also assigned to promote generalization. The results indicate that the intervention promoted several daily positive emotions (e.g., joy, hope, love, and gratitude), increased access to personal resources (e.g., self-acceptance and prosocial relationships with others), and decreased depressive symptoms [57]. Convergent evidence across studies indicates that the gradual progression of targeting kindness from an easy target (i.e., oneself) to a difficult target (i.e., a stranger or a non-preferred individual) is a core component of effective mindfulness interventions [54,55,57,58].

2.3. Parent-Mediated Interventions

Interventions are also designed to be implemented by caregivers with the goals of promoting their children’s prosocial behavior and modeling kind behavior. Such interventions capitalize on the strong influence that parents have on children’s development. One online parent-mediated kindness intervention, “Kind Minds with Moozie,” provides caregivers of preschoolers with brief modules and kindness activities to apply when interacting with their children. Content areas include an overview of kindness along with written and pictorial activities about kindness to self (e.g., saying “good morning” to oneself), animals, and others (e.g., engaging in mutual smiling), and nature (e.g., picking up trash) [59]. Families who engaged in the curriculum reported increases in empathic behavior and resilience in their preschool-aged children, thereby demonstrating the clinical utility of the intervention. Parents can also promote children’s kind behavior through a literature-based approach in which they present children with stories about prosocial interactions and empathetic characters [60]. Reading picture books provides young children, who likely do not yet possess the vocabulary to verbally discuss kind acts, with an opportunity to understand desirable and prosocial behaviors. The effectiveness of this approach is further demonstrated by a study that found that socially themed picture books increase prosocial behavior and empathy in 4–5-year-olds [61]. Parent-mediated storybook interventions also have some cross-cultural support; a study that took place in Indonesia suggested the role of culturally responsive storybook telling as an effective parent-mediated tool that led to increases in caring behaviors in 5–6-year-olds [62].

3. Future Directions

Despite the many widely accepted examples of kindness, there is a lack of consistent definitions or a range of examples of kindness in research. The perspectives of both students and teachers, although from a few studies only, offer valuable references for a comprehensive conceptualization of kindness. It is challenging to study kindness in young children or across various developmental stages (e.g., early, middle, late childhood, and adolescence) using developmentally sensitive methods. In addition to quantitative methods, future researchers may consider using a mix of inductive and deductive qualitative data analysis approaches based on existing literature. Moreover, more studies are needed in populations from diverse ethnicities, economic statuses, and cultural backgrounds. Self-oriented kindness can be an important component of kindness. However, research on the self-kindness of both students and teachers in school contexts is lacking. Furthermore, it is yet to be discovered how and when the components of kindness (kind emotions, cognitions, and actions) become more integrated within a person over time [3].

While research clearly demonstrates the clinical utility of kindness interventions, there is a dearth of literature that specifically assesses adaptations of kindness interventions specifically designed for clinical populations, especially those with difficulty in prosocial behaviors (e.g., youth with disruptive behavior disorders). Future studies should identify the efficacy of such interventions and the necessary adjustments that must be made for programs to be suitable for children with a variety of diagnoses. Additional research should be conducted to identify the long-term effects of existing kindness interventions and whether booster sessions or additional follow-up would promote the sustainability of intervention effects. Moreover, additional research is needed to continue to develop culturally responsive kindness interventions, as recent evidence indicates that the efficacy of kindness interventions is dependent upon cultural context, specifically between independent and interdependent cultures, where self- versus other-oriented kindness is valued and experienced differently [47].

4. Conclusions

In sum, when taking a developmental and ecological approach to studying kindness in young people, some different views of kindness are identified across age/grade levels. Moreover, teachers, as both agents of kindness and models of being kind, should be recognized for their perceived kindness in the larger environment, such as among peers and in school. Most research used prosocial behaviors to represent kindness; however, the conceptualization of kindness is broader than prosocial behaviors, which calls for more research to further the understanding. Emerging research conducted in different regional or cultural contexts revealed both similarities and some differences in the conceptualization of kindness, which has important implications in both research and practice, including intervention design and evaluation. Furthermore, extant evidence demonstrates the benefits of kindness as a predictor of various positive outcomes in children, as well as the desired outcomes of high levels of well-being, supporting the positive role of kindness in fostering individuals’ positive emotions, engagement, and relationships according to the PERMA model [28]. Several interventions have been developed for implementation in school or clinical settings to promote kindness in children. Kindness interventions that include mindfulness-based components and didactic learning can be effective at increasing prosocial behavior and positive emotions. Other than interventions implemented by professionals, one intervention designed for parents has some emerging evidence to support its use. Overall, kindness intervention is at an early development stage and has demonstrated its promise as part of positive psychology intervention; more empirical research is needed to develop and evaluate the interventions that promote kindness in schools and in diverse cultural contexts.