Table 2.

Detailed information on the measurements used in this study

Factors selected	Measurements (detailed information)
Fear of missing out (FOMO)	FOMO was measured by the Fear of Missing Out scale (Przybylski et al., 2013), which comprises 10 items (e.g., “I fear others have more rewarding experiences than me”). All items were valued on a 5-point Likert scale (1 = not at all, 5 = extremely). The Cronbach’s α was 0.798.
Social anxiety	The 4 item-social anxiety scale of Wang, Jackson, and Zhangv (2011), revised from Greca and Lopez (1998), was used to measure social anxiety. Higher scores indicate higher social anxiety. Items were scored on a 5-point Likert scale (1 = never, 5 = always) (α = 0.761). An example item: “I get nervous when I meet new people”.
Loneliness	Loneliness was measured by the children’s loneliness scale developed by Asher, Hymel, and Renshaw (1984). This scale includes 16 items (e.g., “I’m lonely”, “I feel alone”), which were valued on a 4-point Likert scale (1 = very inconsistent, 4 = very consistent). A higher score indicates increased loneliness (α = 0.883).
Self-control	Self-control was measured by the Chinese version self-control scale (Unger, Bi, Xiao, & Ybarra, 2016), which originates from the Tangney self-control scale (Tangney, Baumeister, & Boone, 2004). The scale consists of 17 items (e.g., “I have a hard time breaking habits”, “I am good at resisting temptation”), in which 9 items were scored reversely on a 4-point Likert scale (1 = very inconsistent, 4 = very consistent). The Cronbach’s α was 0.891, and a higher score indicates higher self-control ability.
Teacher-student relationship	The teacher-student relationship scale was adopted from PISA 2015 Assessment and Analytical Framework (OECD, 2017). This scale includes 5 items (e.g., “I get along well with my teacher”, “My teacher treats me fairly”) (α = 0.881), and the higher the score is, the better the teacher-student relationship is.
Peer PSU	Peer PSU was measured by the partner phubbing scale (Roberts & David, 2016). This revised scale includes 9 items (e.g., “My friend places his or her cell phone where they can see it when we are together”), and its Cronbach’s α was 0.878. A higher score indicates higher peer PSU.
Peer attitudes towards smartphone use	These two factors were revised from peers’ attitude on Internet overuse and peer pressure for Internet use (Jin-tao, Chao, Feng-e, Lin-yuan, & Xiao-yi, 2012; Zhou et al., 2019). Peer attitudes towards smartphone use consisted of 6 items (participants were asked “What is your peers’ attitude about the following description?” in 6 aspects, such as excessive reliance on smartphone use and frequent use of smartphone games). Peer pressure for smartphone use contains 7 items (participants were asked “How often did you do the following behaviors under peers’ invites or pressures?”, such as playing games through the smartphone and prolonging time spent on games through the smartphone). For attitude and pressure, higher scores represent more accepted peer attitudes toward smartphone use and more perceived smartphone use pressure from peers. The former’s Cronbach’s α was 0.887, and the latter’s Cronbach’s α was 0.892.
Peer pressure for smartphone use
Friendship quality	Friendship quality was measured by items that were used by Valkenburg and Peter (2007). This measurement includes 4 items (e.g., “I tell my friends about my problems and troubles”, “My friends help me to understand myself better”), whose Cronbach’s α was 0.849. A higher score indicates greater friendship quality.
Parents’ drinking and smoking	Parents’ drinking and smoking behaviors were measured by items revised from YRBS Questionnaire (CDC, 2018). Four items were used in this study to measure fathers’ drinking and smoking and mothers’ drinking and smoking. Example items include “In the past week, how many days did the child’s father drink? (response is from none to 7 days)” or “How many cigarettes did the child’s mother consume in the last week? (response is from none to more than 20 per day)”.
Marital satisfaction	Marital satisfaction was measured using the quality marriage index (Norton, 1983), which includes 6 items (e.g., “We have a good marriage”, “My relationship with my partner makes me happy”), in which items 1–5 were valued on a 7-point Likert scale (1 = totally disagree, 7 = totally agree), and item 6 was valued on a 10-point Likert scale (1 = very unhappy, 10 = very happy). The Cronbach’s α was 0.949, and a higher score means higher marital quality.
Parents’ PSU	Parents’ PSU was evaluated with previous research on problematic smartphone use (Derks & Bakker, 2014; McDaniel & Radesky, 2018). We used 3 items (e.g., “I use my smartphone intensively”, “When my smartphone blinks to indicate new messages, I cannot resist checking them”) to measure parents’ PSU. All items were rated on a 4-point Likert scale (1 = very disagree, 4 = very agree). The Cronbach’s α was 0.703
Technology interference	Items measuring technology interference in parent-child relationships were adopted from McDaniel and Radesky (2018). Parents were asked “On a typical day, about how many times do the following devices interrupt a conversation or activity you are engaged in with your child?” including (a) cell phone/smartphone, (b) television, (c) computer, (d) tablet, (e) iPod, and (f) video game console. Parents responded to each item on a 7-point Likert scale ranging from none to more than 20 times. The Cronbach’s α was 0.731.
Parental mediation (restrictive, active, and co-use)	This study revised the parental mediation scale (Hwang & Jeong, 2015) to form the parental mediation scale on smartphone use for Chinese participants. The revised scale consists of three dimensions: restrictive mediation (e.g., “I set specific rules for using smartphones”), active mediation (e.g., “I explain the disadvantages of overuse of smart devices to my child”), and co-use (e.g., “I accompany with my child to use smart devices to study such as finishing homework, etc.”). Each dimension includes 3 items, which are rated on a 4-point Likert scale. The Cronbach’s α of parental mediation (restrictive, active, and co-use) was 0.797, 0.851, and 0.506, respectively.
Parental engagement	Parental engagement included two aspects: the parents’ engagement in the study (revised from TIMSS 2011 Assessment Frameworks (Mullis, Martin, Ruddock, Sullivan, & Preuschoff, 2011)) and parents’ engagement in daily life (revised from PISA 2009 Assessment Framework (OECD, 2009)). The former’s example item was “My parents ask me what I am learning in school”, and the latter’s example item is “My parents spend time with me talking about TV shows, movies, news or books that interest me”. The Cronbach’s α of the scale was 0.830.
Parent-child relationship	The social relationship network questionnaire, developed by Furman et al., primarily measures the condition of the relationships between an individual and important-others (e.g., parents, teachers, friends) (Buhrmester & Furman, 1985) and was revised to form a parent-child relationship scale, which is popular among Chinese researchers (Zhang, Li, Zhang, Lu, & Wang, 2014). The revised scale includes 23 items (e.g., “Are you satisfied with your relationship with your parents?”, “Are you happy when you stay with your parents?”) and adopted a 4-point Likert scale (α = 0.902). A higher score indicates a better parent-child relationship.
Parents’ attitude towards mobile device use	Parents’ attitude towards mobile devices use was measured by one item, which stated “What is your attitude toward the use of mobile devices?” This item was valued on a 6-point Likert scale (1 = extremely disagree, 6 = very much agree), and a higher score indicates parents with more acceptable attitudes.