Physically punishing a misbehaving child is an ordinary part of parental discipline across continents [1]. In many cultures, hitting, spanking, or slapping a child is nothing out of the ordinary, despite the large body of research claiming that physical punishment is harmful, ineffective, and associated with increased odds of childhood maltreatment ^[2][3][2,3]. Approximately 63% of children are regularly subjected to harsh physical discipline by parents or caregivers, even though The United Nations Committee on the Rights of the Child has stated that physical punishment is a form of violence that threatens a child’s security, and several countries have laws against the practice [4].

A thorough understanding of how physical punishment affects children is not yet available, as some studies suggest physical punishment is associated with neutral or positive outcomes, while other research has shown that the use of physical punishment is linked to a range of negative child and adolescent outcomes [5]. Childhood and adolescent externalizing behaviors are by far the most studied of these outcomes, and research suggests that the use of harsh physical punishment in children is associated with increases in externalizing behaviors over time [3]. This classification of behaviors can be characterized by outward expressions that reflect negatively on a child’s external environment and can be a major risk factor for aggression, delinquency, antisocial behavior and conduct problems. The social learning theory, which posits that parental use of physical discipline teaches children that violence is sometimes effective or necessary, is one approach to explain this phenomenon [6]. Children observe and imitate the behaviors of those around them, especially those they consider to be role models (e.g., their primary caregiver), as highlighted, for example, by a child’s increased likelihood of exhibiting aggressive behavior once they have been subjected to harsh physical punishment themselves [7]. Further, while corporal punishment has been shown to secure immediate compliance and help a parent gain control of a child in the moment, it is not unlikely that instances of physical punishment can escalate into more serious maltreatment. For example, in a study by Afifi et al. [2], harsh physical punishment was associated with increased odds of childhood maltreatment, including sexual, physical, and emotional abuse. These findings indicate that reducing children’s exposure to physical punishment is an effective way to reduce exposure to more severe forms of maltreatment as well.

Ultimately, growing up in a well-balanced environment fosters positive developmental outcomes, and disruption in the safety and stability of a child’s home life may lead to disruption in other domains as well [4]. In the classroom, corporal punishment of a child may worsen their problematic and disruptive attributes, making it difficult for them to succeed academically. For example, corporal punishment has been linked with declines in school engagement as students may be less focused on learning while experiencing heightened levels of stress as a result of the exposure to physical punishment [8]. Another vital part of success in the traditional classroom environment relates to the process of building successful and positive relationships with peers [7]. Effective socialization requires that a child internalizes moral and social norms as he or she learns how to communicate effectively. Unfortunately, studies have shown that this process is disrupted when children are physically punished as the reasons for behaving appropriately are not explained to them [1]. As a result, a child may be rejected by peers as they struggle to effectively interact with others, making their life at school increasingly difficult. This further highlights the importance of encouraging parents to consider alternative methods of discipline since physical punishment at home has spillover effects into other domains and can seriously threaten a child’s potential for success in later life ^[1][3][1,3].

2. Physical Discipline and Externalizing Behaviors in Children

One of the most common methods of parental physical discipline is spanking. Spanking can be characterized as a slap with an open hand, especially on the buttocks, often used to correct undesirable behavior in children ^[9][16]. Unfortunately, studies have found that spanking can actually have the opposite effect ^[10][17]. Literature points towards a link between spanking and higher levels of aggression in children, as well as children’s endorsement of spanking as an effective conflict solution method ^[11][18]. In their longitudinal study, Mackenzie et al. ^[10][17] examined the prevalence of maternal and paternal spanking of children at ages three and five. Rule-breaking, aggression, and destructive habits of the child were measured using the Child Behavior Checklist (CBCL), a commonly administered questionnaire to assess behavioral and emotional problems ^[12][19]. Interestingly, the results of their research indicate that maternal spanking administered at high and low frequency at age five was a significant predictor of higher externalizing behaviors at age nine. These findings go against the argument that normative harsh discipline is not detrimental, suggesting even low-frequency spanking can have a negative effect on a child’s behavioral adjustment. In a similar study, Mulvaney and Mebert ^[13][20] utilized the CBCL and observations of the family environment to examine the impact of corporal punishment (CP) on children’s behavioral problems. This study contained a younger sample, assessing children at 36 months and first grade, and found that CP contributed to negative behavioral adjustment at both time points. A particular strength of this study was that the assumed causal variable (CP) was assessed before the behavioral adjustment of the child, reducing the likelihood that behavioral problems of the child evoked CP from the parents. Nonetheless, temporal precedence is not sufficient for establishing a causal relationship. Even though effect sizes found in this study were small, these findings might still be cause for concern at a societal level given that a large proportion of the world’s children experience CP. An additional problem with the use of correlational longitudinal data is the inability to discern whether a difference found in a construct is due to different initial statuses on a measure, or because of actual rates of growth ^[14][21]. For example, aggressive behavior measured in children at two time points might differ between groups because one group actually increased in instances of aggression or because the children in the sample simply entered the study with different initial levels of the construct. To address this limitation, Grogan-Kaylor ^[14][21] used a hierarchical linear model to investigate the growth trajectory of CP and externalizing behaviors. In his research, the Behavioral Problems Index (BPI) was administered, in which mothers are asked about the degree to which, for example, a child is hyperactive, aggressive, or breaks rules frequently. Results of this analysis showed that the growth of antisocial behavior over time was linear and that the use of CP had a clear effect on this relationship. Specifically, children who had experienced higher levels of CP exhibited higher levels of antisocial behavior than those who did not receive CP. Interestingly, the author found that the strength of the relationship between CP and antisocial behavior was increasingly strong as children grew older, contrary to the belief that parents might begin to use non-coercive discipline tactics as their children develop. Altogether, this study provides methodologically sound support for the conclusion that harsh physical discipline is associated with negative child outcomes. Another common controversy surrounding the use of physical punishment to discipline children is that it does not explain to them why a certain behavior is wrong, nor does it provide alternatives for the child to better handle a challenging situation in the future. In the study by Simons and Wurtele ^[11][18], both parents and children were assessed on the practices and beliefs surrounding corporal punishment using vignettes of moral, social, and prudential transgressions. Interestingly, frequent spanking, as reported by the parents, was the strongest predictor of children’s acceptance of aggressive problem solving. Hitting was seen by children as an effective strategy for resolving interpersonal conflict, as indicated by children’s responses to problem-solving vignettes, and they further generalized that hitting was acceptable in most conflict situations toward both peers and siblings. Although data in this study was based solely on self-report measures and may have been affected by social desirability or recall errors, these findings imply an intergenerational transmission of physical punishment, illustrating that CP experience predicts CP acceptance. The findings regarding physical discipline and externalizing behaviors provide a methodologically firm conclusion: physical discipline, in both high and low frequency, is associated with adjustment and behavioral problems, antisocial behavior, and endorsement of physical punishment as an appropriate problem-solving strategy. Clearly, to best support children’s development, parenting advisors should encourage parents and caregivers to avoid CP as a disciplinary method.

Bidirectionality between Physical Discipline and Externalizing Behaviors in Children

Currently, little is known about the bidirectionality of the relationship between harsh physical discipline and adjustment problems in children; does parental use of physical discipline make children more aggressive, hyperactive, and oppositional, or do these behaviors elicit more physical discipline from parents ^[15][22]? A large body of research supports the hypothesis that physical discipline is related to externalizing behaviors. However, as mentioned previously, a large majority of this research is correlational, and very little is known about the directionality of the relationship ^[16][15]. Unsurprisingly, parenting literature indicates that there are unique contributions from both the parent and the child that shape their relationship and interactions; a child’s behavior can evoke certain reactions from a parent or caregiver, which in turn evokes specific parenting behaviors ^[17][23]. Further, as parents and children develop over time, it is plausible that the nature of this bidirectional relationship can change. As a result, it is important to examine how the parent-child relationship exists and evolves through development to optimize the timing and type of intervention before adverse effects of physical discipline are exacerbated ^[15][22]. In their longitudinal study, Verhoeven et al. ^[15][22] investigated the possibility of a bidirectional relationship between parenting styles and young boys’ externalizing behavior. At four stages throughout their childhood (17, 23, 29, and 35 months of age), mothers reported a broad range of parenting dimensions, including parental support, structure, and physical discipline using questionnaires. The child’s aggressive behaviors and attentional problems were reported using the CBCL. Interestingly, no evidence of bidirectionality was found, suggesting that children’s behavioral problems influenced parenting behaviors; the boys who displayed high levels of externalizing behaviors were the ones who evoked harsh punishment from their mothers and fathers. The authors explain this finding by suggesting that when dealing with a difficult child, parents may lose control and turn more quickly to harsh punishment tactics. Further, the authors posit that the developmental period chosen in the study may have been too early for parenting behavior to display influence on aggressive behavior or attentional problems. Lansford et al. ^[16][15] addressed this limitation by assessing how the relationship between physical discipline and externalizing behaviors develops over the course of time from middle school into adolescence. Mothers reported their discipline practices annually during home interviews, while children’s externalizing behavior was measured using the CBCL administered to the child’s teacher, reducing the likelihood of common method bias. Consistently high levels of externalizing behaviors between ages six and nine were found, where more frequent physical discipline was associated with more frequent externalizing behaviors at all ages. These externalizing behaviors, in turn, were associated with subsequent mild and harsh physical punishment. In the second study, this time consisting of a sample of adolescents aged 10–15, physical discipline and subsequent antisocial behaviors were positively associated, but antisocial behavior was no longer associated with subsequent physical punishment. These findings indicate some evidence for transactional processes between parents and younger children, but these effects appear to weaken as a child reaches adolescence. In the previously mentioned studies, only maternal reports of externalizing behaviors and/or physical discipline were included, overlooking the important role of fathers in the relationship between the two constructs. Unsurprisingly, in two-parent families, children are likely to be spanked by both the mother and father, and the quality of the father-child relationship can have a significant impact on a child’s wellbeing ^[17][23]. To address this gap in the literature, Lee et al. ^[17][23] examined how instances of spanking by mothers and fathers contributed to child aggression in the first five years of life. Associations between the two constructs were measured when the child was one, three, and five years of age. A father-child transactional process was not supported as spanking by fathers was not associated with subsequent increases in child aggression. Further, no evidence was found that fathers changed their rate of spanking as a result of the child’s prior aggression. Results did indicate that mothers spanked more than fathers and that maternal spanking led to increases in child aggression, suggesting that the mothers may have had more opportunities to reinforce this association. In sum, the results of these studies found mixed support for the bidirectional relationship between harsh physical discipline and externalizing behaviors. It is plausible that the characteristics of the sample and measures play a role in determining the direction and strength of the relationship, as highlighted by the fact that evidence for transactional processes was found for younger children and maternal spanking but not for adolescents and father-reported spanking. Clearly, further empirical research is needed to assess the reciprocal effects of parental discipline and externalizing behaviors in children.

3. Potential Moderators: Cultural Normativeness and Parental Warmth

3.1. Cultural Normativeness

Within the study of parental disciplinary practice, the question remains whether all practices are appropriate for all populations [7]. Various studies have shown that parenting behaviors are differentially related to children’s adjustment depending on context, suggesting that conclusions drawn from literature may not be universally applicable ^[18][24]. For example, in a study by Deater-Deckard et al. ^[19][25], a significant association was found between physical discipline and externalizing behaviors in European-American children, leading them to more aggressive behaviors in the school setting, but not in African American children, who showed lower physical aggression scores after physical punishment. Thus, it has been hypothesized that cultural normativeness or ethnic group differences may work to moderate these effects, emphasizing the importance of recognizing that different communities may require different forms of parenting to optimally support children’s development ^[20][26]. Lansford et al. [7] approached the investigation of the role of ethnicity on discipline responses by following a sample of children in the United States from pre-kindergarten to adolescence. Over this period, mothers reported their use of physical discipline at multiple time points, and mothers and adolescents reported a variety of externalizing behaviors at age 16. Their analysis revealed significant interactions between race and physical discipline during the child’s first five years of life in predicting adolescent externalizing outcomes. More specifically, results of their analysis showed that the experience of physical discipline at each time point was related to higher subsequent levels of externalizing problems for European American adolescents, but not for African American adolescents. Adolescent externalizing behaviors included items like getting in trouble with the police, getting into fights, and having difficulties at school. Nonetheless, it is plausible that these interactions have roots other than cultural ones. For example, Pinderhughes et al. ^[21][27] found significant relationships between African American ethnicity, harsher discipline responses, and increased instances of stress in parents, with stress accounting for the ethnic differences in the tendency to use physical punishment. Moreover, in the context of the many difficulties and challenges faced by minority groups, the effect of the added stressor of physical punishment may be diminished in the face of greater concerns. Children’s perceptions of normativeness play an important role in the interpretation of their parents’ disciplinary tactics, as a child who accepts their parents’ behavior as “normal” may not react as strongly when receiving physical punishment. Parents who believe they are acting in a normative way are less likely to act out in uncontrollable anger, and subsequently the message transmitted to the child may not be that their parent is unpredictable and out of control, but instead that the punishment, although unpleasant, is for their own good ^[18][24]. Lansford et al. ^[18][24] examined these effects by conducting interviews with a sample of 336 mother-child dyads from China, India, Italy, Kenya, The Philippines, and Thailand. Their results showed that children’s perceptions of normativeness of physical discipline (e.g., spanking, slapping, or shaking) moderated the association between physical discipline and child aggression. Specifically, more frequent use of physical discipline was associated less strongly with adverse outcomes (in this case, heightened levels of aggression) when perceived as normative by the children. Using the same international sample, Gershoff et al. ^[22][28] found corporal punishment, yelling, and scolding to be associated with child aggression. Interviews were conducted orally in the homes of the participants, and mothers reported how often they used certain discipline techniques, while both mothers and children reported how normal they perceived certain techniques to be in their communities. Measures of the children’s externalizing behaviors were obtained using maternal reports of the aggression subscale of the CBCL. Replicating the results of Lansford et al. ^[18][24], perceptions of normativeness were found to moderate the relationship between CP and child aggression. In other words, although more frequent CP was associated with more aggression, the association was less strong when children perceived CP to be normative in their communities. Nonetheless, it is important to keep in mind that translation of interview questions may have led to a loss of information or misunderstanding. Furthermore, findings cannot be generalized to entire cultural groups or subgroups. The group differences hypothesis explains that patterns of correlations between physical punishment and behavioral problems may differ between cultural contexts. For example, certain behaviors may be adaptive for one cultural group but not another ^[19][25]. Polaha et al. ^[23][9] examined these differences in a sample of African American and European American children and their mothers. The authors used same-source and distinct-source data, postulating that a child could behave differently across contexts, leading to differential perceptions of the child by parents and teachers. The researchers asked mothers of children aged three to five to estimate the frequency of a variety of disciplinary tactics over the past year, as well as hypothetical questions probing disciplinary responses (for example, “What would you do if your child got angry at you and hit you?”), allowing parents to endorse physical and nonphysical strategies. On the other hand, the mother and the child’s preschool or daycare teacher reported measures of child externalizing behavior. The results of their research indicate, as in the previously mentioned studies, that mother-reported physical discipline was associated with more mother-reported externalizing behaviors in children at preschool age. In addition, the authors found a significant two-way interaction with ethnicity, but only when predicting teacher-reported behavioral problems. Specifically, a negative correlation between mother-reported physical discipline and teacher-rated externalizing behaviors was found, but only for African American children. Therefore, using same-source and distinct-source data may contribute unique results to the parenting literature. To sum up, some evidence for the moderation by cultural normativeness was found. Cultural normativeness may work to buffer some of the effects of harsh physical discipline, although the exact mechanisms of this relationship did not provide a firm conclusion. Nonetheless, it appears there are culturally specific reasons for, and responses to, physical discipline which may work to buffer the adverse effects of these practices. Clarifying the role of cultural differences in parental discipline is vital in preventing the development of children with disruptive and aggressive traits into problematic adults.

3.2. Parental Warmth

Over the past few decades, a powerful moderator of the correlation between physical punishment and child behavioral problems has been indicated in studies involving a range of research methods ^[24][12]. Parental warmth, characterized by affection, comfort, and concern, is thought to promote reciprocity and respect between parent and child, leading to fewer disruptive child behaviors ^[25][29]. Physical punishment and parental warmth have been found to be able to co-occur in families, and thus warmth has been hypothesized to act as a buffer against the negative effects of physical discipline as it promotes a positive parent-child relationship ^[9][16]; hence, in a setting where a child misbehaves and receives physical discipline from a mother or father who is generally warm and supportive, a child may be less inclined to perceive the parenting environment to be rejecting, protecting them from acting out ^[24][12]. In their research, Deater-Deckard et al. ^[24][12] hypothesized that the correlation between physical punishment and externalizing behaviors would be highest when maternal warmth was lower in a sample of children between one and nine years old. Families completed interviews, surveys, and home observations probing the harshness of discipline and positive feelings about the child, as well as the child’s externalizing problems. As hypothesized, the moderator effect was present; among the lower warmth mother-child dyads, harsher discipline was positively associated with externalizing behaviors. However, the size of the interaction effect found in this study was small and interview data was cross-sectional. In contrast, Lee et al. ^[9][16] examined the longitudinal associations between maternal spanking and child aggression in a sample of mothers and their children. Between the ages of one and five, mothers reported instances of spanking and their child’s aggressive behaviors, and maternal warmth was consistently observed. Their results indicate that child aggression was highest in groups characterized by low warmth and that increases in spanking predicted increases in child aggression. However, spanking was unrelated to maternal warmth, such that spanking was similarly associated with high levels of child aggression regardless of whether a mother displayed high levels of warmth. Similarly, Mackenzie et al. ^[26][30] administered telephone interviews with mothers in the United States and found that high-frequency spanking at age three significantly predicted externalizing behavior at age five, as indicated by the aggression and rule-breaking subscales of the CBCL. Corresponding to the findings of Lee et al. ^[9][16], no significant moderation of maternal warmth in the relationship between spanking and later externalizing behaviors was found. In the study of Lansford et al. ^[25][29], the research was extended to a diverse set of countries to assess whether and how parental warmth moderates the link between CP and aggression in different contexts. Interviews were conducted with mothers and their children, between the ages of seven and ten, in China, Colombia, Italy, Jordan, Kenya, the Philippines, Thailand, and the United States, with a follow up interview a year later. Mothers were asked how often they used certain CP tactics, and maternal warmth was measured using the Parental Acceptance-Rejection/Control Questionnaire. In this study, both mothers and children completed the CBCL to report externalizing behaviors. Maternal warmth was found to be related to decreases in aggression, while CP predicted subsequent adjustment problems. Significant interaction effects were found in some countries; however, results differed depending on whether mother-reported or child-reported aggression was examined. Lau et al. ^[20][26] examined the contextual factors that might affect the link between physical discipline and child behavioral problems in Black and White families, assessing warmth as a potential moderator. In their study, physical discipline was associated with increases in externalizing problems when children displayed behavioral problems at an early age. However, while parental warmth protected against later behavioral problems among White children, warm attitudes intensified early problems in Black children. Thus, it appeared the moderating effect of parental warmth on externalizing behavior was dependent on the cultural context or ethnic group in which it occurred. In contrast, McLoyd and Smith ^[27][31] used data from a European American, African American, and Hispanic sample of children and found a significant interaction; maternal emotional support (i.e., warmth) moderated the link between spanking and problem behavior for all three racial-ethnic groups. In their study, mothers reported their use of spanking and their children’s behavioral problems, while maternal emotional support of the children was measured during home observations over the course of six years. Findings showed that spanking was associated with increases in behavioral problems over time, but only in the context of low levels of emotional support. Based on the studies mentioned above, there is not yet a firm conclusion about the exact role of parental warmth in moderating the relationship between physical discipline and externalizing behaviors. However, these findings highlight the possibility that even in a trusting, warm, and supportive environment physical discipline may compromise the parent-child bonds and reinforce the behaviors it aims to eliminate.