Screen Media Exposure in Early Childhood and Its Relation to Children ’ s Self-Regulation

Self-regulation, the ability to control thoughts, emotions, and behavior for goal-directed activities, shows rapid development in infancy, toddlerhood, and preschool periods. Early self-regulatory skills predict later academic achievement and socioemotional adjustment. An increasing number of studies suggest that screen media use may have negative e ﬀ ects on children ’ s developing self-regulatory skills. In this systematic review, we summarized and integrated the ﬁ ndings of the studies investigating the relationship between young children ’ s screen media use and their self-regulation. We searched the ERIC, PsycINFO, PubMed, and Web of Science databases and identi ﬁ ed 39 relevant articles with 45 studies. We found that screen time in infancy is negatively associated with self-regulation, but ﬁ ndings were more inconsistent for later ages suggesting that screen time does not adequately capture the extent of children ’ s screen media use. The ﬁ ndings further indicated that background TV is negatively related to children ’ s self-regulation, and watching fantastical content seems to have immediate negative e ﬀ ects on children ’ s self-regulatory skills. We suggest that future studies should take the content and context of children ’ s screen media use into account and also focus on parent- and home-related factors such as parental behaviors that foster the development of self-regulatory skills.


Introduction
Self-regulation is a multidimensional construct that represents an individual's ability to manage thoughts, feelings, and actions to support goal-directed behavior across changing contexts [1]. Children's self-regulation skills predict their cognitive and social outcomes such as school readiness, academic achievement, and socioemotional adjustment [2][3][4][5]. Studies in recent years suggest that self-regulation is related to children's use of screen media. On the one hand, there are studies suggesting that a high dose of regular exposure to screen media is related to poorer self-regulation skills in children [6]. On the other hand, there are findings indicating that children who are rated by their parents as having poor self-regulation skills are allowed to use screen media more often [7]. Considering that children are frequently exposed to screens from an early age onwards [8][9][10][11][12][13] and the predic-tive role of early self-regulation for later outcomes, it is important to understand how children's self-regulation relates to their screen media use. The purpose of this review article is to provide an overview of this relationship by focusing on the age period until six, the prime years for the development of self-regulation [2,14].
1.1. Defining Self-Regulation. Self-regulation has been investigated by researchers across different fields of study, leading to a lack of consistency in its definition and measurement and a lack of conceptual integration across disciplines [1,[15][16][17][18][19][20]. Jones et al. [21] identified over 40 unique terms in the literature that define regulation-related skills; however, researchers agree that the two terms that stand out in the self-regulation literature are executive functions and effortful control [22][23][24][25].
Executive functions are mostly studied from a cognitive perspective and are characterized as top-down processes that help individuals engage in goal-directed behaviors and control and regulate automatic processes and prepotent responses [26]. Executive functions have been conceptualized as a unitary construct [27] or a unitary construct with dissociable components like working memory (for storing and manipulating information in mind), inhibitory control (for inhibiting prepotent responses and behaviors), and cognitive flexibility (for flexibly adjusting to new demands and changing perspectives) [28,29]. Executive functions are usually measured with standardized lab-based tasks that assess separate components (e.g., backward digit span task to measure working memory) or a combination of these (e.g., Tower of Hanoi task to measure planning). Children's early executive functions predict later school readiness and academic achievement [30][31][32]. Parental behaviors (scaffolding, autonomy support, and controlling), attachment security, and socioeconomic status and risk are associated with children's executive functions [33][34][35][36][37].
In contrast to executive functions, effortful control has mostly been studied from a socioemotional perspective and is thought to be a critical component of emotion regulation [38]. Effortful control is the temperamental dimension that corresponds to individual differences in the ability to regulate emotions and actions [39][40][41]. Skills like inhibitory control, voluntary control of attention, conflict resolution, error detection and correction, and planning are thought to be part of this construct [42]. Effortful control is typically measured via parent or teacher reports (e.g., Child Behavior Questionnaire by [43]), but laboratory tasks to measure inhibitory skills and direct observations of behavior in naturalistic settings are used as well [44]. Children's effortful control is positively associated with prosocial behavior and social competence and negatively associated with internalizing and externalizing problems [45,46]. Demographic and psychosocial risk, along with parental responsiveness and parental positive and negative control behaviors, is associated with children's effortful control [47][48][49].
Researchers have proposed a unifying framework for self-regulatory skills that combines the two different works of literature of executive functions and effortful control. Zhou et al. [25] proposed an integrated model of selfregulation encompassing both of these constructs based on their commonalities (e.g., inhibitory control) and correlations between behavioral tasks measuring executive functions and parent and teacher reports measuring effortful control [31,50]. More recently, Nigg [20] emphasized the need to integrate executive functions and effortful control, and Bailey and Jones [22] argued that a unifying framework would provide a more comprehensive account of regulatory skills. Here, we employ such a unifying framework for selfregulatory skills and focus on the studies investigating the relationship between young children's screen media use and self-regulation.

Understanding How Screen
Media Use Relates to Self-Regulation. There are several nonmutually exclusive hypotheses about how children's cognitive and social abilities-in-cluding self-regulation-may be associated with their use of screen media [51]. One explanation is that the quality time that could be spent alone or with caregivers on enriching and educational activities is displaced with screen time that provides fewer opportunities for cognitive and social growth [52][53][54]. Given the strong links between children's selfregulatory skills and parental behaviors like sensitivity and scaffolding [34,49,55], it is plausible that self-regulation shows a less than optimal development when the frequency and quality of parent-child interactions suffer due to excessive screen media use by children.
Another hypothesis linking children's self-regulation to their screen media use suggests that compared to screen media, other activities such as schoolwork may seem less exciting and less interesting for children as screen media often contains fast-changing scenes and attention-grabbing properties [51]. In a similar vein, Singer [56] proposed that children's attention to TV is maintained via perceptually salient auditory and visual changes, and thus, regular exposure to TV may lead children to rely on the environment rather than on internal goals and motivations to maintain focused attention. As self-regulation requires top-down control of emotions, thoughts, and actions and is linked to the ability to control attention [57][58][59], the bottom-up effects of screen media on attention may be disruptive for the development of self-regulatory skills. Thus, the first question that this review aims to answer is whether children's screen time is negatively associated with their self-regulatory skills. But all screen time is not equal. Children can spend time on traditional vs. interactive media, where the former corresponds to TV watching and the latter encompasses activities such as playing video games, video chatting, and watching videos. When spending time on interactive devices, children may be more likely to engage in goal-directed activities that necessitate the use of regulation-related functions. Therefore, a related question we aim to answer is whether the association between screen time and self-regulation differs for traditional and interactive media.
Whether screen time has adverse effects on child development is particularly debated for infants. World Health Organization (WHO) [60] and the American Academy of Pediatrics [61] recommend no screen time for infants younger than age two with the exception of video chatting, but research shows that infants are exposed to screens starting from a young age [8,10,62]. An early exposure to TV and TV viewing in infancy are associated with negative developmental outcomes in terms of attention and language [63]. Any negative effects of screen exposure in infancy may be related to the fact that infants learn best through social interactions and fail to acquire new knowledge from screen media, including infant-directed DVDs and YouTube videos [64][65][66][67][68]. Thus, another aim of this review is to examine whether screen exposure in infancy is detrimental to the development of self-regulation.
Despite many findings showing negative associations between screen time and child outcomes, there are also studies reporting no associations or positive relations [69]. Inconsistent findings may point to problems in measuring children's screen time as well as to the importance of other 2 Human Behavior and Emerging Technologies aspects of screen media use such as content (e.g., educational vs. entertainment) and context (e.g., parental mediation of child media use) [63,69,70]. The content children consume on screens shows variation as some shows/applications are only entertainment-oriented, whereas others contain both education-and entertainment-related elements; some are more realistic, and others tend to be more fantastical. Hence, another aim of this review is to reveal the relations between children's self-regulation and the content they consume on screens.
Apart from the content, contextual factors such as parent-child interactions during screen media use and the use of screen media during different family routines such as bedtime and meals may be important. One such contextual factor is whether children use screen media as a primary or secondary activity. While children are involved in a primary activity such as individual play and play with their parents, they are often exposed to the television running in the background [71][72][73][74]. Background TV negatively affects caregiver-child interactions, children's play behaviors, and focused attention [75][76][77]. Given that the development of self-regulation is related to both caregiver-child interactions and children's attentional control skills, background TV may have detrimental effects on children's self-regulation. Thus, another goal of this review is to summarize the findings pertaining to the relationship between background TV and selfregulation.
Finally, another contextual factor that may be important is parent-related factors such as parental restrictions on children's screen media use. A recent study with a large sample size (>10,000) of US elementary school children reported that children had a lower risk of later frequent use of online technologies if families had certain rules on children's TV use such as when and what to watch [78]. Hence, a question to be answered is whether parental practices in terms of regulating children's screen media use have a protective role against the potentially negative effects of screen media. Furthermore, any negative effects that screen media use might have on children's self-regulation may be alleviated by positive parental behaviors such as parental responsiveness and scaffolding that support the development of self-regulatory skills. Thus, the final goal of this review is to examine the role of moderating and protective parent-related factors.

Current Review
To date, no systematic review article has comprehensively integrated the findings of studies that investigate the relations between young children's screen media use and selfregulation. Some of the previous review articles focused only on one aspect of self-regulatory skills such as executive functions or one aspect of screen media use such as TV viewing [63,79]. Other review articles were either not systematic [80] or omitted relevant articles by using a limited or highly specialized (e.g., health-related) pool of databases [79,81]. Thus, the current study is aimed at providing a systematic review of young children's (age < 6) screen media consumption and their self-regulation by conducting a thorough database search and identifying the current gaps in the liter-ature. The questions that this review aims to answer revolve around three main topics, namely, the relation of children's self-regulation to (1) screen time, (2) screen media content, and (3) screen media context. To reiterate, our research questions regarding each of these three dimensions are as follows: (1) Is there a negative association between children's screen time and self-regulation?
(a) Does this relationship differ for traditional and interactive media?
(b) Is screen time in infancy particularly detrimental to self-regulatory skills?
(2) Is there a relationship between children's selfregulation and the content they are exposed to on screens?
(3) Are contextual factors related to children's screen media use relevant to children's self-regulation?
(a) Is background TV negatively associated with children's self-regulation?
(b) Are there any moderating variables like parenting behaviors or parental rules regarding screen media use that may influence the relationship between children's self-regulation and screen media use?

Method
The current review followed the guidelines of the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement for reporting the search strategy and eligibility criteria [82].
3.1. Search Strategy. Using the (("self-regulation" OR "executive function * " OR "effortful control") AND ("media exposure" OR "mobile device" OR smartphone OR tablet OR technology OR TV OR "digital media" OR computer OR "screen media" OR "screen time") AND (infant * OR child * )) keywords, we searched the ERIC, PsycINFO, PubMed, and Web of Science databases in March 2021. Bibliographies of the relevant articles were further hand searched.

Inclusion and Exclusion
Criteria. We used the following eligibility criteria for the studies to be included in this review: studies had to have an assessment of children's self-regulation and an assessment or manipulation of screen media use. Studies had to have children younger than age six and/or their parents as participants. For longitudinal studies, children had to be younger than age six at the first measurement point. Studies had to be published in peer-reviewed journals and written in English to establish a form of quality check. Unpublished dissertations and conference proceedings were excluded to ensure that the selected articles had undergone rigorous peer review. There was no limitation regarding the publication date of the studies. The first author removed the duplicates, and all authors independently screened the articles based on titles and abstracts. Discrepancies were resolved by discussion. The full texts of the remaining articles were screened for eligibility by the first author by using the criteria listed above. Figure 1 shows the search and elimination process of the articles.

Data Extraction.
For each article, the following information was extracted: (1) type of the study (correlational vs. experimental), (2) design of the study (cross-sectional vs. longitudinal), (3) sample size, (4) age range of participants, (5) information related to the socioeconomic status of the participants, (6) country where the study took place, (7) how children's self-regulation was measured, (8) how children's screen media use was measured or how the screen content/use was manipulated (for experimental studies), (9) control variables/covariates, and (10) main findings.
The second and third authors entered information about each study into a summary table, and the first author verified this information (see Table 1). If the studies included effect sizes, these values are reported in Table 1.

Quality Assessment.
We assessed the quality of each study by using the Downs and Black checklist [83], which comprises 27 items. All of the items were not relevant to each type of study design; therefore, similar to Faelens et al. [ Figure 1, 3,987 articles were identified through database search (ERIC: 106, PsycINFO: 1,340, PubMed: 895, and Web of Science: 1,646), and seven additional articles were identified through backward citation search. After the removal of the duplicates and the elimination process based on titles and abstracts, 60 articles remained. Out of these 60 articles, 39 articles (having 45 independent studies) matched the inclusion criteria and were included in this review. Except for two studies published in 1973 and 1979, all studies were published between 2010 and 2020. Here, we will first summarize the findings of the studies that investigated the relations between children's screen time and self-regulation by focusing on the studies testing concurrent and predictive relations in order. In the same section, we will summarize the findings pertaining to the time spent with traditional vs. interactive media and screen exposure in infancy. Then, we will review the findings of how screen media content and context (e.g., background TV and parent-related factors) relate to children's selfregulatory skills (see Table 2 for a categorization of studies according to different themes).

Screen Time
4.2.1. Concurrent Relations between Screen Time and Self-Regulation. Seven studies examining the relationship between children's self-regulation and the time spent with traditional media found children's TV viewing amount to be associated with poorer self-regulatory skills (e.g., poorer executive functioning and more self-regulatory problems) [6,[85][86][87][88][89][90]. In contrast to these findings, two studies reported nonsignificant relations [91,92], and one reported a positive association between TV viewing and executive functions [93] where the sample had a relatively low amount of TV viewing ðM ðSDÞ = 1:22 ð0:93Þ hoursÞ compared to the samples in other studies. The examination of the relationship between children's self-regulation and interactive media use similarly produced inconsistent findings. Three studies did not report significant relations between interactive media use and executive functions and self-control [86,91,92]. In contrast, a positive relation was reported by Yang et al. [94]; however, the unique variance in executive functions that was explained due to the time spent playing electronic games was relatively low (0.001). In other work, sleep was shown to be a moderator where children's effortful control was negatively related to tablet use if they received less sleep but positively related to game player use if children slept more [95]. Yet, the regression coefficients of these screen time predictors were relatively small (β ' s = 0:0007 and 0:0009). Overall, current evidence does not seem to suggest any strong relations between interactive media use and children's self-regulatory skills.
In contrast to the studies that differentiated between traditional and interactive media, several studies used a measure of total screen media use spanning both the time spent watching and interacting with screen media devices. Four out of these five studies reported negative relations between self-regulation and screen time or a lack of compliance with screen time recommendations [96][97][98][99], and one study reported null findings [100].
In sum, the majority of the findings indicate a negative relation between TV viewing and children's self-regulatory skills; however, it cannot be concluded that TV viewing is detrimental to the development of self-regulatory skills since some studies reported no significant relations between these variables.. Regarding the use of interactive media, null findings and small effect sizes indicate that it may not be strongly related to self-regulation.

Predictive
Relations between Screen Time and Self-Regulation. While most of the studies investigated concurrent relations between children's screen time and selfregulatory skills, longitudinal studies focusing on early screen time's predictive capacity for later self-regulation 4 Human Behavior and Emerging Technologies have been conducted as well. Studies assessing screen time in infancy (age ≤ 2) reported that early screen exposure was negatively related to later self-regulatory skills [7,69,100,101]. For preschool-aged children, findings were more inconsistent as some studies reported that higher screen time predicted poorer self-regulation ( [88,102,103] for application use) and others reported null findings ( [104] (after including parent-and home-related control variables); [7,103] (for program viewing); [105]). Regarding the traditional versus interactive media distinction, longitudinal studies did not provide sufficient evidence as only three studies measured these separately [7,103,105]. Except for McNeill et al. [103] that demonstrated a negative association between early application use and later executive functions, other studies found nonsignificant relationships between interactive media use and self-regulation.
Longitudinal studies mostly focused on the predictive role of early screen media exposure for later self-regulation, but there were some studies examining whether early selfregulatory skills may predict later screen media use. Relatedly, it has been demonstrated that infants with longer crying durations and children with more difficult temperaments (such as children with higher irritability and distractibility) are allowed to have longer screen time [106][107][108]. In a similar vein, two studies reported that early self-regulatory skills were negatively associated with later screen time [7,109], but not all studies supported this claim [100].
Overall, similar to cross-sectional studies, longitudinal research reported mixed findings in terms of the relationship between screen time and self-regulatory skills. These mixed findings were especially evident for preschool-aged children.

Screen Time in Infancy.
Studies were in consensus that screen time in infancy is negatively related to children's selfregulatory skills. To summarize, early (age ≤ 2) screen exposure was found to be positively associated with selfregulatory problems [97] and negatively associated with later executive functions [100,101] and self-regulatory skills measured via parent, teacher, and observer reports [7]. To complement these findings, an earlier onset age of screen viewing was found to be negatively associated with executive functions [6]. Overall, these findings suggest that early screen exposure might be detrimental to children's developing self-regulatory skills. It must also be noted that the effects of early exposure may depend on the screen media content since Barr et al. [110] reported that early exposure to adult-directed but not child-directed TV was negatively associated with later executive functions.         10 Human Behavior and Emerging Technologies

24
Human Behavior and Emerging Technologies In most of the studies that collected data on TV content, the content was classified as either educational or entertainment (i.e., content without an educational value). In terms of the relationship between watching educational content and self-regulatory skills, studies showed both negative [6], positive [87], and null findings [93,[111][112][113]. Similarly, while some studies reported that watching entertainment content was positively related to self-regulation ( [112] for low-risk children; [93,113]), others demonstrated a nonsignificant relationship [6]. Thus, regarding TV content, the findings demonstrate some contradictions.
In terms of the relationship between electronic game play and self-regulation, our current knowledge is limited. One study demonstrated that children show better cognitive flexibility after a short amount of physical play compared to touchscreen play [114]. How the content of electronic games may be related to children's regulatory skills was only investigated by one study that reported negative relations between action content and inhibitory control and no significant relations between action and prosocial content and composite executive function measures [94]. Thus, more studies are needed to investigate how game content may be related to self-regulation in young children.

Fantastical Content.
Physically impossible and hence fantastical events are commonly used in child-directed TV and videos. Comprehension of fantastical events may be cognitively taxing due to their novelty and rarity in daily life, resulting in excessive consumption of resources [115][116][117]. It has been suggested that executive functions and processing fantastical events may rely on the same cognitive resources; thus, watching fantastical events may have immediate negative effects on executive functioning (e.g., [118]). To test this hypothesis, a series of studies investigated the short-term effects of watching fantastical content on young children's executive functions and reported poorer performance on executive function tasks after watching fantastical events [115][116][117]119]. These findings were complemented by higher activation of the brain and frequent and shorter eye fixations while watching a higher number of fantastical events, potentially indicating more cognitive effort [116]. An exception was the study by Kostyrka-Allchorne et al. [120] reporting that inhibitory control showed an increase after watching unrealistic content, albeit the effect size for this increase was rather small (η p 2 = 0:025). Unlike other studies using cartoons, this study used movies consisting of a narrator along with story-related images, which may have rendered the procedure more similar to book reading than watching a typical cartoon.
Interacting with fantastical events such as playing a fantastical game may have different effects on executive functions compared to watching these events. Interactivity may allow multimodal stimulation, such that children can see, hear, touch, and manipulate images and characters on the screen. This multimodal stimulation may render the perception of fantastical events as more realistic [118]. So far, only one study investigated the differences between the immedi-ate effects of watching vs. interacting with fantastical content and reported poorer outcomes in terms of inhibitory control for watching compared to interacting [118]. More studies are needed to investigate the differential effects of watching and interacting with fantastical events on children's executive functions.
Apart from whether fantastical content is presented in an interactive way or not, the pace of presentation may also matter. Attention-grabbing properties of screen media such as fast pace may trigger bottom-up attentional processes [56] and negatively affect self-regulatory skills, which require topdown control of attention [2]. So far, studies testing the effect of slow vs. fast pace while keeping the number of fantastical events similar in both conditions did not report any significant effects of pace on children's executive functions [117,120]. On the contrary, children showed a poorer delay of gratification ability after watching a fast-paced compared to a slow-paced show in Lillard and Peterson [121]; however, the fantastical content was a confound in this study since the fast-paced show was fantastical but the slow-paced one was realistic.
In sum, the majority of the studies investigating the immediate effects of fantastical content on young children's executive functions reported negative effects with effect sizes ranging from medium to large. Furthermore, the negative effects of watching fantastical content on behavioral outcomes were supported by studying eye movements and brain activation patterns.

Long-Term Effects.
In terms of how the content of screen media relates to children's self-regulatory skills, the majority of the studies were concerned with the immediate negative effects of viewing or interacting with fantastical content. On the other hand, two early experimental studies investigated the long-term effects of viewing different types of TV content on children's various developmental outcomes such as behavior problems, peer relations, prosocial behaviors, and self-regulation. Their findings showed that children's tolerance of delay, namely, the ability to voluntarily wait for materials or adult attention when these are not immediately available, increased after a long-term exposure to prosocial TV content such as cooperation, sharing, and sympathy and decreased after being exposed to aggressive TV content such as physical violence and verbal aggression [122]. Similarly, a long-term exposure to prosocial TV content led to positive changes in children's social interactions, imaginative play, and aggression but not in self-regulation [123]. These two studies are the only ones that provide information about the effects of long-term manipulation of screen media content.
In general, the studies examining the relationship between children's self-regulation and screen media content demonstrated (1) immediate negative effects of watching fantastical content on executive functions and (2) mixed findings in terms of the relationship between educational and entertainment TV and self-regulation. background TV was positively related to children's selfregulation problems [113] and negatively related to executive functions ( [112], only for high-risk children; [124]). Similarly, watching adult-directed shows, which may function as background TV [125], was negatively related to children's cognitive skills, including executive functions [87,110]. Additionally, children more frequently exhibiting difficulties in regulating their emotions and behavior were exposed to longer durations of TV during meals and background TV [98]. Overall, regarding background TV, studies suggest that it is negatively related to young children's ability to self-regulate.

Parent-Related Factors.
Parental behaviors can facilitate or hinder the development of children's self-regulatory skills. Three studies found that after controlling for parentrelated factors such as hostile and positive parenting, general well-being, and anxiety, early screen time (age ≤ 3) was still negatively related to later self-regulation [7,101,102]. On the contrary, Blankson et al. [104] found that early TV exposure was negatively associated with later executive functions, but this relationship was no longer statistically significant after controlling for mothers' scaffolding behaviors and features related to the home learning environment such as the presence of cognitively stimulating toys. This study differed from the three studies reporting negative relations in that maternal behaviors were measured via observation rather than self-report.
Instead of using parent-related factors as control variables, two studies examined the moderating role of these factors between children's screen media use and selfregulation. These studies did not report a significant moderating role for parental inconsistency and responsiveness [112] and parental sensitivity [98]. Overall, there is weak evidence for a protective role of positive parental behaviors against the probable negative effects of screen media use.
Parental restrictions on children's use of screen media may also be relevant to the relationship between children's screen media use and self-regulation as parents may limit their children's screen time and the content they are exposed to on screens. Parental limitations on children's TV time and content predicted better cognitive and social skills, including executive functions and self-control [87]. However, after controlling for demographic factors and screen time and content, the restrictions did not significantly predict children's cognitive and social outcomes. Contrary to expectations, Yang et al. [93] found that only if the parental restrictive approach was at a low level, TV viewing duration was positively related to executive functions. The authors argued that parents might be more restrictive for children with poorer executive functioning skills. Overall, the findings of these two studies about parental restrictions are not conclusive, and more research is needed to examine the moderating role of parental restrictions.

Discussion
The main purpose of this review was to provide a comprehensive summary of the literature regarding the relations between young children's screen media use and their selfregulatory skills. Specifically, we focused on the relation of children's self-regulation to screen time, screen media content, and screen media context. The key findings in response to the six questions that this review aimed to answer can be listed as follows: (1) screen time is not consistently negatively associated with children's self-regulation; (2) inconsistent findings were reported for both traditional and interactive media; (3) screen exposure in infancy is negatively related with self-regulation; (4) watching fantastical content seems to have immediate negative effects on children's executive functions, and watching educational content does not seem to have positive effects; (5) background TV is negatively related to children's self-regulatory skills; and (6) studies mostly do not lend support to the claim that certain parenting practices and behaviors are protective against the potential negative consequences of screen exposure. In the discussion that follows, we will elaborate on each of these key findings.

Screen Time.
Studies testing concurrent and predictive relationships between screen time and self-regulation produced inconsistent results. An explanation of this inconsistency may be that screen time by itself is not a completely adequate measure of screen exposure. It has been suggested that children's screen exposure should not only be assessed in terms of screen time but also in terms of parental attitudes towards media use, parental mediation of media use, and the amount of background TV in the household [69]. Another potential explanation of inconsistent findings is related to how screen time is measured. Most of the studies assessed screen time by parent estimate; however, parental reports may be biased as parents have been found to underreport (36% of parents) or overreport (35% of parents) their young children's use of mobile devices [126]. It is possible that parents report incorrect information due to social desirability bias or their lack of awareness about their children's media use. Asking parents to keep a diary of their children's screen media use could lead to more accurate assessments of screen time. Only a small number of studies reviewed here used the diary method to collect more detailed data [110,112,113]. Collecting diary data from parents could both render the classification of the media content easier and enable further investigation of screen time such as whether a bulk of screen time (e.g., 2 hours of TV after lunch) has different effects than more scattered screen time throughout the day (e.g., 1 hour of TV after lunch and 1 hour of TV after dinner).
Consistently, studies found that screen exposure in infancy predicts poorer self-regulatory skills. Coupled with the findings showing that an earlier onset of screen exposure is negatively associated with executive functioning [6], these findings suggest that screen exposure before age two is detrimental to the development of self-regulatory skills. One way for early screen exposure to have a damaging effect is that TV/videos may stimulate low-level instead of high-level attentional processing via rapid visual changes [56], which could impair attentional control skills that underlie selfregulation. Supporting this hypothesis, a recent study showed that preschool-aged children had lower attentional 27 Human Behavior and Emerging Technologies control skills if they had a longer duration of touchscreen use from toddlerhood to preschool ages [127]. Another explanation for why early screen exposure is related to poorer self-regulation may be that the content being watched is mostly incomprehensible for infants. Just like watching fantastical content has immediate negative effects on preschool-aged children's executive functions, watching TV/videos and especially adult-directed content may create a cognitive load and have short-term negative effects on emerging self-regulatory skills of infants. Finally, infants are wired to learn from social interactions. From a young age onwards, they prefer to look at faces, prefer speech and particularly child-directed speech over other signals, and pay attention to social cues [128][129][130][131]. The lack of interactivity in screen media seems to create an obstacle for infant learning. Supporting this argument, Myers et al. [132] found that 17-to 25-month-olds demonstrated word and pattern learning by interacting with an adult over FaceTime but failed to do so after watching a prerecorded video of the same person. In terms of self-regulation, behaviors such as learning to wait and dealing with frustration are likely to be more easily learned from social interactions and by observing caregivers as role models instead of watching the interactions between the characters on screen.
In terms of the distinction between traditional and interactive media, we do not have conclusive evidence. For both types of screen media use, inconsistent findings have been reported. Particularly, there is no evidence for a strong connection between interactive media use and self-regulation in children. An explanation of these findings may be that interactive devices can be used both passively (such as for watching videos) and actively (such as for playing games and using applications), and these different types of use may have different effects on children's attention and behaviors related to self-regulation. A drawback of most of the studies that assessed the amount of children's interactive media use was that how and for what purposes children use mobile devices was not measured.

Screen Media Content.
What children watch on TV may be more important than how much they watch [63]. Experimental studies seem to agree that watching fantastical content has immediate negative effects on children's executive functions and that children are likely to show a poorer performance on executive function tasks and more brain activation after watching fantastical content which indicates that the processing of fantastical events requires cognitive effort from young children. A future direction may be to investigate the cumulative long-term effects of watching fantastical content since all studies so far examined immediate effects. Whether watching fantastical events creates a similar cognitive load for older children may also be examined by future studies since compared to younger children, older children (and adults) may find fantastical events easier to process. Furthermore, if processing fantastical content is taxing for young children's cognitive resources, it can be tested whether using a simple and explanatory language of the events to accompany the visuals would alleviate this cognitive load.
Apart from fantastical content, some studies investigated whether watching educational content benefitted children's self-regulatory skills. Out of five studies coded for TV content, only one reported positive associations between watching educational content and self-regulation. A recent analysis of child-directed applications that were advertised as educational showed a low educational quality for most of the applications analyzed [133]. Although we are not aware of such an analysis for TV shows, it may be that the TV shows/cartoons categorized as educational may likewise have low educational value. There is also the possibility that educational content is more important for the development of vocabulary and general knowledge but not for the development of self-regulation.
In terms of whether watching entertainment TV relates to children's self-regulation, the findings were inconsistent as some studies showed a positive relationship and others reported null findings. An explanation of these inconsistent findings may be that the TV shows that were categorized as entertainment TV may vastly differ from each other in terms of their narrative structure, action content, and pace (e.g., Tom and Jerry and SpongeBob). More fine-grained analyses of the content (e.g., fantastical content, action content, and prosocial content) and the way the content is presented (e.g., use of visually/auditorily salient features such as sound effects, the presence, or absence of dialogue) seem to be necessary.

Background TV.
Consistently, studies found that background TV and watching adult-directed content are negatively associated with children's emerging self-regulatory skills. It is known that high-quality interactions and parental behaviors are associated with better development of selfregulatory skills [34,55]. One way for background TV to be related to children's self-regulation is through decreasing the quantity and quality of parent-child interactions and positive parental behaviors towards children [75,76,134,135]. Another way for background TV to have an effect on self-regulation may be through children's attentional skills. Experimental studies showed that young children sustain their attention on toys for shorter periods of time while the TV is on in the background [77,136]. Frequent exposure to background TV may have cumulative negative effects on children's attentional control skills that are thought to lay the foundation for self-regulation [58].

Parental Behaviors and Parental Restrictions on Screen Media
Use. Spending quality time with parents and experiencing positive parenting behaviors such as sensitivity and scaffolding may alleviate the negative effects that screen media use may have on child development. Studies mostly did not report such a protective or moderating role of parental behaviors. The only piece of evidence indicating a protective role of parents came from Blankson et al. [104], where the negative association between screen time and selfregulation was rendered insignificant after controlling for parental scaffolding and the home learning environment. Importantly, the studies that did not report a significant role for parenting measured aspects of parental behaviors via self- 28 Human Behavior and Emerging Technologies report while the study reporting a significant role for parental scaffolding used an observational method to assess parental behaviors. We suggest that future studies use observation to assess parental behaviors and focus on specific behaviors that provide support for the development of self-regulation, such as autonomy support and scaffolding [55,137]. The role of parental restrictions in the relationship between children's screen media use and self-regulation was not studied widely. More studies are needed where the role of parental restrictions is interpreted in relation to parental education and family income since these factors are significantly associated with parental attitudes towards children's screen media use [108,138].

Limitations and Future
Directions. The theoretical approaches that aim to explain how the development of selfregulation might be related to children's use of screen media were not tested by the majority of the studies. For instance, the displacement hypothesis argued that longer durations of screen time may be detrimental since screen time might displace the time that could be spent with caregivers on activities that support the development of self-regulation [52]. One way to test this hypothesis would be to measure the proportion of time children spend on doing different activities like watching TV, participating in sports, being engaged in hobbies, and doing homework [139]. To date, no study directly tested this hypothesis in relation to the development of self-regulation. Another hypothesis linking screen media use to children's attention and cognitive development suggests that low-level, perceptually salient visual changes found in child-directed TV/videos capture children's attention so that over time, children may rely on external stimuli more than internal goals to guide attention [56]. Current evidence suggests that the pace of the program does not have any immediate effects on children's executive functions [117,120], but more studies are needed to understand how formal features such as editing and the presence of sudden visual effects have an effect on children's attention and self-regulation.
We know that children from low-income countries use the Internet the least, and their digital experiences are less documented [13]. Thirty-seven of 39 studies reviewed here were conducted in high-income countries, and the remaining two studies were conducted in upper-middle-income countries (classified according to the [140]). More studies are needed to investigate how children's use of screenbased technologies in low-income countries relates to their self-regulation. Another limitation of the current literature was the lack of focus on the content of screen media children consume. As for the studies that measured content, they tended to omit information about how different content categories (such as educational and entertainment) were coded. Furthermore, although numerous findings demonstrate that playing aggressive video games is associated with attention problems and aggressive thoughts and behaviors in children and adolescents [51,141,142], only one study [122] investigated the effects of watching aggressive content on children's self-regulation. More studies are needed to investigate how watching or interacting with aggressive and action content relates to young children's self-regulation.
Although we mostly focused on the negative associations between children's screen media use and self-regulation, it may be that certain types of screen media use may have positive effects. For instance, one of the factors that was overlooked by the studies reviewed here was whether and how joint media engagement, in other words, sharing media experiences with another partner [143] such as a caregiver or a sibling, may have different effects compared to using screen media alone. Another factor that may lead to more positive outcomes may be interacting with prosocial content. Playing prosocial video games where game characters help and support each other is associated with positive outcomes such as increased prosocial behaviors and decreased aggressive cognition for children and adults [142,[144][145][146]. Future studies should examine the immediate and long-term effects of exposure to prosocial interactive content on children's self-regulation. Furthermore, our current knowledge about whether and how touchscreen play affects children's attention and selfregulation is highly limited. It may be that an interactive use of screens with high-quality apps may yield positive effects. Finally, since physical activity has been shown to promote the development of executive functions [147], games and game consoles that combine screen-based activity with physical activity (such as Just Dance and Nintendo Wii Fit) may yield positive outcomes in terms of self-regulatory skills.
In the current review article, we deliberately did not focus on the studies that investigate the relationship between children's screen media use and their attention-related behaviors, such as focused attention and inattention, and ADHD-related behaviors such as impulsivity and hyperactivity. Given that attentional control is thought to be related to the development of regulation-related behaviors [28,148], future review studies and meta-analyses can focus on the findings of the studies investigating the relationship between children's screen media use, attention-related behaviors, and attention problems.

Disclosure
The present study was presented at the Budapest CEU Conference on Cognitive Development (2022) and APA Technology, Mind, and Society Conference (2021) as a poster.