Tomisaki et al.
Child Adolesc Psychiatry Ment Health(2018) 12:53
https://doi.org/10.1186/s13034-018-0258-8

RESEARCH ARTICLE

Child and Adolescent Psychiatry
and Mental HealthOpen Access

The relationshipbetween the development of social
competence and sleep in infants: a longitudinal
study
Etsuko Tomisaki1, Emiko Tanaka2, Taeko Watanabe3, Ryoji Shinohara4, Maki Hirano2, Yoko Onda2,
Yukiko Mochizuki2, Yuko Yato5, Noriko Yamakawa6, Tokie Anme2* and the Japan Children’s Study Group

Abstract
Background: Many reports argue that sleep is important for children’s health, learning, and academic performance.
The purpose of this longitudinal study was to examine the association between sleep and the development of social
competence in infants.
Methods: This study was conducted as part of a Japan Science and Technology Agency (JST) project. Caregivers
responded to the Japan Children’s Study Sleep Questionnaire when children were 18 months old. The interactions ofcaregivers and children were observed when children were 18, 30, and 42 months old, and rated with the Interaction
Rating Scale, which is a measure of social competence.
Results: Nocturnal sleep duration of more than 10 h and an earlier bed time than 22:00 were significantly correlatedwith two trajectory groups (low point and high point transition groups) of children’s social competence at 18, 30, and42 months. Further, total sleep duration of more than 12.25 h and an earlier bed time than 22:00 were significantly
correlated with the trajectory of children’s social competence at 18, 30, and 42 months.
Conclusions: Sleep duration and sleep onset time are important factors in children’s development of social
competence.
Trial registration The ethics committee of the JST approved this study on March 19, 2001. The registration number is356-1.
Keywords: Social competence, Nighttime sleep duration, Total sleep duration, Sleep onset time, Longitudinal study
Background
Social competence is an ability to take another’s perspective, learn from experiences, and apply these abilities tothe ever-changing social landscape [1]. Evidence links
social competence to education, employment, criminal
activity, substance use, and mental and physical health[2, 3]; additionally, high social competence is valued byorganizations and employers, and promotes success in*Correspondence: anmet@md.tsukuba.ac.jp
2
Graduate School of Comprehensive Human Sciences, Universityof Tsukuba, 1‑1‑1 Tennodai, Tsukuba‑shi, Ibaraki‑ken 305‑8577, Japan
Full list of author information is available at the end of the article

jobs [4]. Around 18 months, children recognize themselves in a mirror [5]. Further, they show empathy [6] andengage in cooperative interactions with others [7]. For
the development of these abilities, children must recognize that they themselves and others may possess different perspectives [8]. To gain this recognition, interactions
that occur with caregivers are important [9]. Social competence is receiving an increasing amount of attention
in Japan, partially due to rising awareness of problems
with bullying and hikikomori (children who are not sickbut still cannot go to school because of reasons such as
bullying, being unable to understand what teachers say,and loneliness in class; they stay home most of the time

© The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License(http://creat​iveco​mmons​.org/licen​ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium,provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license,
and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creat​iveco​mmons​.org/
publi​cdoma​in/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Tomisaki et al. Child Adolesc Psychiatry Ment Health(2018) 12:53

without any contact with society). Some studies havereported that deficits in social skills predict depressive
symptoms and peer victimization [10, 11]. Others havereported that problem groups have lower social competence in elementary school [12]. From these reports, it
can be said that social competence is an important factor
for bullying and hikikomori.
Optimal sleep is known to be essential to normal
growth and development, as well as to emotional healthand proper immune system functioning [13, 14]. Further,sleep is critical to brain and body development [15–17].
Inadequate sleep can adversely affect all aspects of achild’s biopsychosocial health [18]. Many reports haveexamined the link between sleep and behavioral problems [19–24] in children. Dahl reported that inadequate
sleep results in tiredness, lack of attentional focus, lownegative affect thresholds (irritability and rapid frustration), and difficulty in moderating impulses and emotions [20]. Furthermore, inadequate or insufficient sleep
is related to behavioral and emotional regulation [25–27],
which are among the factors of social competence.
In the study of sleep, researchers must consider manyfactors, such as “waking up time” (the time a child wakesup), “sleep onset time” (the time a child goes to sleep),“daytime nap duration” (the total time a child sleeps during a nap), “nocturnal sleep duration” (the total time achild sleeps during the night), and “total sleep duration”(the total time a child sleeps including nap time). Further, sleep rhythm (whether sleep onset time and waking
up time are consistent during a week) is also important.
These factors have accordingly received considerable
attention in the literature. In this study, we looked atthree factors: “sleep onset time”, “nocturnal sleep duration” and “total sleep duration”.
“Late bedtimes” are correlated with problematic behaviors [28–38]. “Eveningness” has been correlated withscores on a composite measure of antisocial behavior,rule-breaking, attention behavior problems, and conductdisorder symptoms in boys, and to relational aggression
in girls [39]. Late sleep onset time has been correlatedwith irritation in junior high students [39, 40]. Additionally, late sleep onset time has been correlated withaggressive behavior [22, 41] and the development of verbal impairments [42] in infants.
Short nocturnal sleep duration has been negatively
correlated with approachability and positively correlated with hyperactivity–impulsivity [21, 43, 44], while
increased nocturnal sleep has been correlated withincreased approachability at 3, 6, and 11 months [44].
Further, children aged less than 3.5 years with shortnocturnal sleep durations showed an increased risk ofhigh hyperactivity–impulsivity scores and low cognitive
performance at 6 years compared with children who

Page 2 of 11

slept 11 h per night, after controlling for potentiallyconfounding variables [21]. Furthermore, 3 to 5-yearold children had significant correlations between sleep
duration and social engagement [25].
Total sleep duration was associated with emotional
problems [45, 46]. Furthermore, a shorter daytime sleep
duration was correlated with emotional regulation
at 12 months of age [44]; late bedtimes and less total
sleeping time appear to be associated with and predictive of social-emotional problems in infants and toddlers [38].
As stated, sleep is important. Unfortunately, Japanesechildren had the shortest total sleeping time in a sample of 18 countries, with an average of 11.6 h per day
from birth to 36 months [47]. Further, the bedtimes ofJapanese children are reported to be late [48–50], andlate bedtimes are specifically associated with shorter
nocturnal sleep durations [51]. Late bedtime and shortnocturnal and total sleep duration at a young age maystrongly affect many aspects of development. For thesereasons, we examined the association of sleep withsocial competence.
Although large, the literature on sleep contains few
studies that have examined sleep’s association withsocial competence. The purpose of this longitudinal
study was to examine the association between sleeping
and the development of social competence in infants.
We hypothesized that children with late bedtimes andshort nocturnal and total sleep duration may also have
low social competence scores.

Methods
ParticipantsParticipants were drawn from the Japan Science andTechnology Agency (JST) project, which operated in
two cities in Japan (Osaka and Mie) from 2003 to 2009.
Four hundred and sixty-five caregiver-child dyads participated in the JST project; we analyzed participants in
its observation component. Children in caregiver-childdyads were aged 18 months (206 dyads), 30 months(305 dyads), and 42 months (158 dyads). Regarding trajectory of social competence, dyads who answered thepaper at 18 months and participated at least twice in theobservation component at 18 months, 30 months, and42 months (207 dyads) were analyzed. We conducted aone-way ANOVA between these groups (i.e., 18-, 30-,
and 42-month dyads). No significant differences were
found between these groups regarding gender (F = 0.01,
P = 0.94) or presence of siblings (F < 0.01, P = 0.97).
Dyads were observed at 18, 30, and 42 months; social
competence was rated using the Interaction Rating
Scale (IRS).

Tomisaki et al. Child Adolesc Psychiatry Ment Health(2018) 12:53

Page 3 of 11

Measures

Procedure

Caregivers were asked to record a daily sleep log oneach day of the week regarding sleep/wake status on theJapan Children’s Study Sleep Questionnaire (JCSSQ).
This measure’s reliability and validity on weekdays
have been supported [52, 53]. Sleep/wake status wasrecorded in the daily sleep log, including sleep onset
time, morning waking time, and sleep period, whichwere the variables extracted for analysis.
The Index of Child Care Environment (ICCE) isbased on the Home Observation for Measurement of
the Environment (HOME) scale [54]. This measure’s
reliability and validity have been supported [55–57].
The ICCE is a screening questionnaire used to evaluate the quality of a childcare environment. It contains
13 items in four subscales: (1) human stimulation (i.e.,
work together with your partner to raise your child),(2) avoidance of restriction (i.e., number of times in aweek you slap your child), (3) social stimulation (i.e.,
go to the park with your child), and (4) social support(i.e., have child care support). Some items are rated ona five-point Likert scale (from 1 to 5); others require a
simple yes-or-no response.
The Interaction Rating Scale (IRS) is used in a controlled laboratory environment to obtain a rating of achild’s social competence, based on observations of the
caregiver–child interaction. We have conducted observations at 18, 30, and 42 months. Trained evaluators
whose concordance rate was more than 90% evaluatedmother–child interactions in videos. This measure’s
reliability and validity have been supported [58–60].
The IRS includes 70 behavioral and 11 impression score
items in 10 subscales. Five subscales examine the child’ssocial competence: (1) autonomy, (2) responsiveness,(3) empathy, (4) motor regulation, and (5) emotion regulation. The other five subscales assess the caregiver’s
parenting skills: (6) respect for autonomous development, (7) respect for responsiveness development, (8)respect for empathy development, (9) respect for cognitive development, and (10) respect for socio-emotional
development. One item assesses the relationship’s overall synchronicity. Each subscale assesses the presence of
behavior (1 = Yes, 0 = No). The IRS checklist, composedof 25 items examining the behavior of the child toward
the caregivers (e.g., child looks at the caregiver’s face asa social reference) and 45 items examining the conductof the caregiver, was completed by an observer. The
total score for each child is the sum of subscale scores(maximum = 25). A higher score indicates a higher levelof social competence. We used only the child’s social
competence subscales in this study.

Primary caregivers (mostly mothers: 97.1%) provided
demographic data and completed the ICCE and theJCSSQ at 18 months (Tables 1, 2) and posted them.
Table 1 Demographic information at 18 months
Items

18 months (n = 207)n%

Genders
Boys

102

49.3

Girls

105

50.7

Siblings
0

103

49.8

1

80

38.6

2

21

10.1

3

1

0.5

No answer2

1.0

Family type
Nuclear family

177

85.5

Extendend family

28

13.5

No answer

2

1.0

Mother’s age
20–29

54

26.1

30–39

143

69.1

40–49

10

4.8

No answer––

Father’s age
20–29

36

17.4

30–39

138

66.7

40–49

24

11.6

50–

1

0.5

No answer

8

3.9

Mother’s career
No

67

32.4

Yes

114

55.1

No answer

26

12.6

Family annual income< 2 million JPY

34

16.4

2–4 million JPY

46

22.2

4–6 million JPY

85

41.1

6–8 million JPY

26

12.6

8–10 million JPY

9

4.4≥ 10 million JPY

7

3.4

–

–

No answer

Using child care center
No

78

37.7

Yes

125

60.4

No answer

4

1.9

JPY Japanese yen

Tomisaki et al. Child Adolesc Psychiatry Ment Health(2018) 12:53

Table 2 The distribution of sleep at 18 months
Items

18 months (n = 207)n%

5 ~ o’clock

1

0.5

6 ~ o’clock

54

26.1

7 ~ o’clock

110

53.1

8 ~ o’clock

31

15.0

9 ~ o’clock8

3.9

10 ~ o’clock

1

0.5

11 ~ o’clock2

1.0

19 ~ o’clock2

1.0

20 ~ o’clock

28

13.5

21 ~ o’clock

102

49.3

22 ~ o’clock

56

27.1

23 ~ o’clock

14

6.8

24 ~ o’clock

5

2.4

0

12

5.8

~1

20

9.7

~2

118

57.0

~3

47

22.7

~4

10

4.8

4~

–

–

5~

3

1.4

7~

1

0.5

8~

15

7.2

9~

98

47.3

10~

76

36.7

11~

12

5.8

12~

2

1.0

8~

1

0.5

9~

11

5.3

10~

30

14.5

11~

79

38.2

12~

69

33.3

13~

14

6.8

14~

3

1.4

Waking up time

Sleep onset time

Daytime naps duration (h)Nocturnal sleeping duration (h)Total sleeping duration (h)In observation, caregiver–child interactions wererecorded using five video cameras (one at each of thefour corners of the room and one in the center of the ceiling). Recordings were made when the children were 18,30, and 42 months old. Each dyad was escorted to a playroom (4 × 4 m) furnished with a small table and chairs
for the caregiver and child. We asked each caregiverto teach his or her child a prescribed task, which wasPage 4 of 11

slightly difficult for the child to accomplish alone (building a small house with some building blocks). During thehouse-building task, the caregiver gave instructions toand assisted the child, as in daily life. We considered thatthe task began when the caregiver received the building blocks and ended upon the completion of the houseand the caregiver’s tidying up of the play area. Observation typically lasted for 1–5 min. An observer then completed the IRS checklist based on the video recordings ofinteractions.
Analysis

The Statistical Analysis System (SAS; v9.3) was used forall data analysis. We performed Spearman rank-ordercorrelations between the 18-month-olds’ sleep ratings (nocturnal sleep duration, total sleep duration, andsleep onset time) and social competence at 18, 30, and42 months.
A trajectory of social competence growth was developed for each child using the semi-parametric groupbased trajectory method (Proc Traj, an extension of SAS
for Windows, v.9.1; SAS Institute, Inc., Cary, North Carolina) [61–63]. The selection of the optimal number oftrajectory groups was based on the Bayesian information
criteria (BIC). In trajectory analysis, subjects with somemissing longitudinal variables were included in the analysis. The base model assumed the missing data to be random. The missing data in this research do not depend on
the data value, meaning the missing data are random [64],so the base model fits the data well. Maximum likelihood
estimation was used to estimate the model parameters.
After establishing the trajectories of social competencefrom 18 to 42 months old, the model computed the effectof predictor variables on the probability of trajectorygroup membership. We checked the probability of eachvariable in terms of which trajectory group it may belong
to. A logistic regression analysis was used.
Next, we examined the contributions of a group of nocturnal sleep duration and sleep onset time, and anotherof total sleep duration and sleep onset time in distinguishing group memberships for child social competence
trajectories. Group memberships were made at the cutoff
point of 25th percentile. A multinomial logistic regression function was used.

Results
Demographic data are shown in Table 1. Two hundredand seven caregiver-child dyads were analyzed regarding the trajectory of children’s social competence. The
percentage of only children at 18 months was 49.8%, and85.5% lived in a nuclear family.
Table 2 shows the distribution of sleep variables(i.e., waking up time, sleep onset time, daytime nap

Tomisaki et al. Child Adolesc Psychiatry Ment Health(2018) 12:53

Page 5 of 11

duration, nocturnal sleep duration, total sleep duration)
at 18 months of age. The mean (standard deviation: SD)
sleep onset time was 21.56 (0.89); 49.3% of children went
to sleep between 21:00 and 22:00. The mean nocturnal
sleep duration was 9.64 (0.85) hours; 47.3% of children
slept from 9 to 10 h. The mean total sleep duration was
11.56 (1.02) hours per day; 38.2% slept from 11 to 12 h
in total. Sleep onset time was found to be positively correlated with nocturnal sleep duration (r = 0.43, P < 0.001)
and total sleep duration (r = 0.28, P < 0.001).
The mean score on the IRS was 21.35 (3.63) at
18 months, 22.32 (3.02) at 30 months, and 22.96 (2.66)
at 42 months. Table 3 shows correlations between nocturnal sleep duration, total sleep duration, and sleep
onset time and social competence. Nocturnal sleep duration was significantly positively correlated with emotion
regulation scores (r = 0.18, P = 0.01) at 18 months. At
30 months, sleep onset time was significantly positively
correlated with emotion regulation (r = 0.12, P = 0.04). At
42 months, sleep onset time was significantly positively
correlated with emotion regulation (r = 0.18, P = 0.02),
motor regulation (r = 0.26, P < 0.01), and total social competence (r = 0.23, P < 0.01). Nocturnal sleep duration was
positively correlated with emotion regulation (r = 0.17,
P = 0.03) and total social competence (r = 0.18, P = 0.02).
Further, total sleep duration was positively correlatedwith total social competence (r = 0.18, P = 0.02).
Figure 1 indicates the trajectory of the developmentof social competence from 18 to 42 months. We identified groups using a group-based trajectory model. In
order to determine the optimal number of trajectories
needed to describe the transition of social competencefrom 18 to 30 and to 42 months, we fitted models with
one, two, three, four, and five profiles, based on BIC. The
BIC was − 1515.28 for one trajectory, − 1517.88 for two,Fig. 1 Trajectory of social competence− 1525.27 for three, − 1528.35 for four, and − 1536.98 for
five, when considering social competence alone. Using
the BIC criterion, the one-group model fit the best. However, the AIC criterion in one-group was − 1509.59 andin two-group was − 1506.50, hence a two-group model
was selected. The trajectory groups were divided into twogroups: low point and high point transition groups. The
two groups’ score came close at 42 months, but there wasa significant difference between the average score of thetwo groups (Fig. 1).
All variables were checked in terms of which trajectorygroup they belonged to. Gender and the presence of siblings at 18 months emerged as significant factors. Further,“Work together with your partner to raise your child”
emerged as a significant factor. Regarding sleep variables,
total sleep duration and sleep onset time emerged as significant factors (Table 4).

Table 3 Correlations between sleep and child’s social competenceSocialcompetence

Autonomy

Responsiveness EmpathyMotorregulation

Emotional
regulation

r

r

P

r

P

r

P

r

r

P

− 0.03

0.67

0.11

0.43

0.11

0.10

− 0.040.59

0.06

0.10 − 0.06
0.01

0.91

0.18

0.01

− 0.02

0.80

0.03

0.08

0.06

0.41

− 0.001.00

0.04

0.64 − 0.12
0.48

0.09

0.11

0.12

0.04

− 0.00

0.99

0.02

0.67

0.02

0.75

0.01

0.82

P

Sleep onset time (18 months)

0.07

0.30

0.02

0.83

Nocturnal sleeping duration (18 months)

0.08

0.24

0.05

0.49

Total sleeping duration (18 months)

0.02

0.76

0.05

0.45

Sleep onset time (30 months)

0.08

0.14

0.03

0.58

− 0.030.57

Nocturnal sleeping duration (30 months)
Total sleeping duration (30 months)

0.05

0.39

Sleep onset time (42 months)

0.23

Nocturnal sleeping duration (42 months)
Total sleeping duration (42 months)

0.42

P

− 0.01

0.88

0.05

0.37

0.08

0.17

0.04

0.50

0.02

0.73

0.02

0.73

< 0.01

0.11

0.19

0.06

0.45

0.10

0.23

0.26

< 0.01

0.18

0.02

0.18

0.02

0.06

0.44

0.06

0.45

0.12

0.14

0.06

0.44

0.17

0.03

0.18

0.02

0.09

0.28

0.07

0.35

0.10

0.20

0.14

0.07

0.12

0.13

Italic values indicate significance of P value (P < 0.05)

Tomisaki et al. Child Adolesc Psychiatry Ment Health(2018) 12:53

Page 6 of 11

We divided children into two groups, one by nocturnal sleep duration and sleep onset time, and anotherby total sleep duration and sleep onset time. The participants were divided into two groups with sleep onset
Table 4 Correlation between the trajectories of children’ssocial competence
Items

Low vs. highanalysis
Regression P
coefficient

Genders2.90< 0.01

Siblings

2.91< 0.01

Family type

0.30

0.76

Mother’s age− 0.55

0.58

Father’s age− 1.02

Mother’s career

0.31

0.54

Annual family income

0.59− 0.79Using child care center
Play with your child
Read books to your child
Sing songs with your child

0.43

0.00

1.00

− 0.68

0.50

0.97

0.33

1.73

0.08

Work together with your partner to raise your child

1.95

0.05

Eat meals together as a family

0.86

0.39

Go grocery shopping with your child
Go to the park with your child
Go to friends’ or relatives’ house
Have child care support− 0.20

0.85

1.17

0.24

− 0.950.34

0.67

Have consult
Talk with your partner about your child

0.50− 0.01

1.00

0.61

0.54

When your child splits milk

0.24

0.81

Number of times in a week you slap your child

1.12

0.26

Sleep onset time

2.05

0.04

Nocturnal sleeping duration

1.85

0.07

Total sleeping duration

2.10

0.04

Italic values indicate significance of P value (P < 0.05)

times above the 25th percentile (before 22:00, n = 132,
63.8%; after 22:00, n = 73, 36.2%) and sleep duration
below the 75th percentile (less than 10 h, n = 165,
79.7%; more than 10 h, n = 42, 20.3%). The sleep duration percentile differed from the sleep onset time percentile as we wanted to include any duration less than
11 h, given that previous literature has shown associations between sleep durations less than this amountand increased risk of high hyperactivity–impulsivity scores and low cognitive performance [21]. The
sleep duration variable was therefore set at the 75th
percentile. For the same reason, the participants weredivided into two groups with total sleep duration below
the 75th percentile (less than 12.25 h, n = 160, 77.3%;
more than 12.25 h, n = 47, 22.7%). Sleep onset time
was found to be significantly positively correlated withnocturnal and total sleep duration (r = 0.40, P < 0.01;
r = 0.27, P = 0.04).
Using these groups, we created four new variables(X) denoting nocturnal duration and sleep onset time:(1) nocturnal sleep duration more than 10 h and sleep
onset time before 22:00 (n = 68); (2) nocturnal sleep
duration more than 10 h and sleep onset time after
22:00 (n = 7); (3) nocturnal sleep duration less than
10 h and sleep onset time before 22:00 (n = 97); and (4)nocturnal sleep duration less than 10 h and sleep onset
time after 22:00 (n = 35; Table 5).
An additional four variables (Y) denoting total sleep
duration and sleep onset time were also created: (1)total sleep duration more than 12.25 h and sleep onset
time before 22:00 (n = 64); (2) total sleep duration morethan 12.25 h and sleep onset time after 22:00 (n = 11);(3) total sleep duration less than 12.25 h and sleep
onset time before 22:00 (n = 96); and (4) total sleep
duration less than 12.25 h and sleep onset time after
22:00 (n = 36; Table 5).

Table 5 New variables from sleeping
Sleeping variables
Sleep onset timen%

Nocturnal sleeping duration

New variables
X1

X2

X3

0

0

68

32.9

0

0

0

0

1

7

3.4

1

0

0

1

0

97

46.9

0

1

0

1

1

35

16.9

0

0

1

n

%

New variables
Y2

Y3

Sleeping variables
Sleep onset time

Total sleeping duration

Y1

0

0

64

30.9

0

0

0

0

1

11

5.3

1

0

0

1

0

96

46.4

0

1

0

1

1

36

17.4

0

0

1

Tomisaki et al. Child Adolesc Psychiatry Ment Health(2018) 12:53

In the multinomial logistic regression analysis, we
examined the relative contributions of two parenting
practices at 18 months: “Work together with your partner to raise your child,” and the caregiver slapping theirchild or not, because there are reports that slapping thechild is correlated to social competence [65–68]. The
child’s gender and the presence of siblings at 18 months
were entered as covariates in order to control for theseeffects on child social competence development. The
results indicated that children with high social competence trajectories were more likely to have an earlier
sleep onset time and sleep longer at night (regression
coefficient = 2.15, P = 0.03; Table 6).
Furthermore, children with high social competence
trajectories were more likely to have an earlier sleep
onset time and have more total sleep (regression coefficient = − 2.01, P = 0.05; Table 7).

Discussion

Table 6 Multinomial
logistic
regression
analysisof sleeping new variable X and trajectory of social
competence
Low vs. highmultiple analysis
P

Genders

2.35

0.02

Siblings

1.23

0.22

Work together with your partner to raise your child

1.69

0.09

The caregiver slapping their child or not

0.92

0.36

New variableX1[sleep onset time, nocturnal sleeping duration = 1,0]

0.50

0.62

1.42

0.16

New variableX3[sleep onset time, nocturnal sleeping duration = 1,1]

2.15

0.03

− 2.000.05

New variableX2[sleep onset time, nocturnal sleeping duration = 0,1]
Constant

BIC = − 1104.67

Italic values indicate significance of P value (P < 0.05)

Items

Low vs. highmultiple analysis
Regression
coefficientP

Genders

1.57

0.12

Siblings

0.75

0.46

Work together with your partner to raise your child

1.62

0.11

The caregiver slapping their child or not

0.67

0.50

New variableY1[sleep onset time, total sleeping duration=1,0]

0.82

0.41

New variableY2[sleep onset time, total sleeping duration=0,1]

1.15

0.25

New variableY3[sleep onset time, total sleeping duration=1,1]

2.01

0.05

− 1.180.24

Constant
Italic values indicate significance of P value (P < 0.05)

We found that sleep onset time before 22:00, sleeping atnight for more than 10 h, and total sleep duration of morethan 12.25 h at 18 months of age are important for thedevelopment of social competence. Late bedtimes havebeen associated with problematic behavior [22, 28–42],and short nocturnal sleep duration has been negatively
associated with approachability and positively associatedwith hyperactivity–impulsivity and social engagement[21, 25, 43, 44]. Further, total sleep duration has been

Regression
coefficient

Table 7 Multinomial
logistic
regression
analysisof sleeping new variable Y and trajectory of social
competence

BIC = − 1110.89

Relationship between sleep variables (nocturnal sleep
duration, total sleep duration, and sleep onset time)and social competence

Items

Page 7 of 11

associated with emotional problems [45, 46]. IRS has
evidence in terms of discriminant validity for pervasive
development disorder (PDD), attention deficit/hyperactivity disorder (ADHD), and abused children. Children with PDD, ADHD, and abused children have beenreported to have lower levels of empathy and self-control
in areas such as motor regulation and emotional regulation compared to children without these conditions [58].
Though the correlation between sleep variables and IRS
is weak, these reports support our findings.
Sleep onset time had a weak correlation with motor
regulation and emotion regulation at 42 months. Emotion regulation is the child’s ability to adjust his or her
emotional state to a comfortable and appropriate level.
Motor regulation is the child’s physical focus on a giventask, and high regulation is neither overactive nor underactive. As previously indicated, late bedtimes have been
associated with problematic behavior [22, 28–42, 69].
One study showed that 4-year-old children whose sleep
onset time was late were aggressive [69]. Further, anotherstudy showed that 3-year-old children whose sleep onset
time was late had short tempers [41]. Our results extend
these findings to indicate that emotion and motor regulation skills are associated with earlier sleep onset time.
Short nocturnal sleep duration has been negatively
associated with approachability and positively associated with hyperactivity–impulsivity and social engagement [21, 25, 43, 44]; our results support this finding.
In 42-month-olds, social competence was significantly
associated with sleep onset time and sleep duration. It
is interesting that 18-month-olds’ sleep patterns wereTomisaki et al. Child Adolesc Psychiatry Ment Health(2018) 12:53

more closely related to social competence at 42 monthsof age than at 18 or 30 months of age. As noted previously, infant sleep patterns may affect behavior at older
ages [21, 33, 69]. Children who slept less than 11 h before
they were 3 years old were found to show hyperactivity–impulsivity at 6 years of age [43]. Further, children
for whom parents felt their child’s sleep time was shortshowed aggressive behavior 14 years later [70]. Thus,
infant sleep may affect social competence later in life.
Total sleep duration and sleep onset time influenced
the trajectory of the development of social competence
in children. Total sleep duration appears to be associatedwith social-emotional problems [38]. Further, reports
have indicated that children with short nocturnal sleep
duration are at an increased risk of high hyperactivity–
impulsivity and low cognitive performance [21]. Furthermore, a significant association between sleep onset timeat 3 years of age and quality of life in the first year of junior high school has been reported [71]. Our results therefore indicate that sleep onset time and sleep duration areimportant to the development of social competence.
Many other sleep patterns require further examination.
Research has reported that late bedtimes are specificallyassociated with shorter nocturnal sleep duration [21]. In
this study, a relationship was found between bedtimes
and sleep duration (nocturnal and total sleep). Hence,
examining only one of these factors may be insufficient.
It is therefore necessary to examine sleep duration andsleep onset time together.
Participants’ demographic data, sleep variables, and social
competence

Participants’ demographic data indicated that they accurately represented the general population of Japan. The
mean (SD) sleep onset time in this study was somewhat
later than in the paper by Kohyama et al. [72], which was
21.26 (1.01). However, the means of nocturnal and total
sleep duration were similar to results reported by Kohyama [65], which were 9.52 (0.94) h and 11.65 (1.27) h,
respectively. The children who participated in Kohyama’s
study [72] were aged 12–23 months; as the children were
18 months old in our study, age may account for some ofthis difference.
We chose 18 months as the age to begin measuring
sleep because sleep patterns vary in the first few yearsof life, and it is easier to compare sleep patterns whenchildren exhibit a given pattern consistently. Most children sleep through the night by 18 months and, whilesome children may continue to take two or more naps,
most children take only one nap [73]; we therefore examined children aged 18 months old. Further, in Japan,
infant health checkups are scheduled at 3, 6, 9, 18, and36 months, which facilitated our assessments.

Page 8 of 11

Japanese children have the shortest total sleep duration of 18 examined countries [47]; total sleep durationin this study was close to the amount reported previously [47]. Touchette et al. argue that nocturnal sleep
duration of 11 h or more before age 3.5 is necessary for
unimpaired cognitive performance at age six [21]. In thepresent study, only 7.1% of children were sleeping morethan 11 h at night; hence, Japanese children may not be
sleeping enough. They also fall asleep late: 30% of them
go to sleep after 22:00 [49]. In this study, average sleep
onset time was close to 22:00, and 36.3% of children went
to sleep later than 22:00.
The mean score on the IRS was over 20 for every age
group, showing that 70–80% of children of various ages
have a score of above 20 [74]. This scale assesses the interaction between child and caregiver; as noted previously,
the interactions that occur between child and caregiverare important to the development of social competencein the child [9]. The caregivers who participated in thisJST project were interested in learning about child rearing, which may have had some impact on the high scoresthat were observed.
Social competence correlates with many other factors,
including gender, birth order [75], family dynamics [76],and family background [77]. Identifying the most important associated factors is necessary to achieve the greatest insight and understanding of the role of sleep in later
development. In this study, the trajectory of the development of social competence was related to gender andpresence of siblings at 18 months. The trajectory of social
competence was not related to ICCE scores; however,there was a trend toward a positive relationship betweensocial competence and co-parenting at 18 months. We
therefore included these three variables—gender, siblings, and co-parenting—in our analysis. Studies havealso reported that punishment affects social competence[65–68]; we therefore used this variable too.
Regarding social competence, between low pointand high point transition groups, the point came closer
at 42 months. Social competence is known to develop
through training [78]. It keeps developing, but unfortunately, the total score of IRS is 25 points. If IRS had
higher points, the high point transition group may have
had higher points at 42 months, and there could havebeen more difference between the two groups. To resolve
this problem, we created another scale called the Interaction Rating Scale between Children (IRSC) [79]. Further
investigation is needed to find differences between thetwo groups using the IRSC.
Limitations and suggestions for future researchThis study has certain limitations. First, we examinedchildren only at ages 18, 30, and 42 months; futureTomisaki et al. Child Adolesc Psychiatry Ment Health(2018) 12:53

studies should use assessments that are more frequentand study older children. Second, the children’s caregivers provided information regarding sleep variables;
however, the JCSSQ has verified the reliability of parent
reports [52, 53]. Third, we examined sleep patterns onlyat 18 months of age. Future research could expand thisstudy’s results by including older children and measuring
sleep patterns at different ages.
Sleep onset time and sleep duration affect the development of social competence. The present results indicate that Japanese children’s sleep duration is short andsleep onset time is late. As mentioned previously, infant
sleep may affect children later in life. There are reportsthat show associations between late sleep onset time at
3 years of age and low quality of life in the first year of
junior high school [71]. Japanese children’s short sleep
duration and late sleep onset time may have some association with social competence problems in later years.
Further investigation of the role of sleep in the development of social competence is necessary. This information
may become a protective factor in preventing childhood
problems.

Page 9 of 11

Availability of data and materials
The datasets used and/or analyzed during the current study are available fromthe corresponding author on reasonable request.
Consent for publication
Not applicable.
Ethics approval and consent to participate
The ethical standards set by the JST were followed. Owing to the age of thechildren, we carefully explained the purpose, content, and methods of thestudy to the caregivers. The caregivers were also told that they had the rightto withdraw from the experiment at any time. Each caregiver then signed an
informed consent form. To maintain the confidentiality of the participants,
personal information was collected anonymously and stored securely usinga private ID system. Further, all image data were stored on a password-protected disk; only researchers with the chairperson’s permission were granted
access. The ethics committee of the JST approved this study on March 19,
2001. The registration number is 356-1.
Funding
As part of the project “Exploring the effective factors on the child’s cognitiveand behavior development in Japan,” this research was supported by the R&D
Division of Brain-Science & Society, the JST Research Institute of Science andTechnology for Society (RISTEX), and a Japanese government Grant-in-Aid for
Scientific Research (23330174).

Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Received: 23 October 2017 Accepted: 6 December 2018

Conclusions
We examined the association between sleep and thedevelopment of social competence in infants. Nocturnal sleep duration, total sleep duration, and sleep onset
time had positive correlations with children’s social
competence. Sleep is an important factor in the development of children’s social competence. Follow-up studies are necessary to investigate the role of sleep in social
competence.
Abbreviations
JST: Japan Science and Technology Agency; IRS: Interaction Rating Scale; ICCE:
Index of Child Care Environment; JCSSQ: Japan Children’s Study Sleep Questionnaire; HOME: Home Observation for Measurement of the Environment.
Authors’ contributions
All authors participated in the drafting or the revision of the manuscript. In
addition, ETo participated in the design of the study and performed the statistical analysis. ETa, TW, RS, MH, YO, and YM participated in the interpretationof data. YY and NY collected the data. TA supervised and led the design of thestudy. All authors read and approved the final manuscript.
Author details
1
Keio University, Tokyo, Japan. 2 Graduate School of Comprehensive Human
Sciences, University of Tsukuba, 1‑1‑1 Tennodai, Tsukuba‑shi, Ibaraki‑ken
305‑8577, Japan. 3 Shukutoku University, Chiba, Japan. 4 Health Science
University, Yamanashi, Japan. 5 College of Letters, Ritsumeikan University,
Kyoto, Japan. 6 Clinical Research Institute, Mie-Chuo Medical Center, National
Hospital Organization, Tsu, Japan.
Acknowledgments
We wish to thank all of the participants in the JST project.
Competing interests
The authors declare that they have no competing interests.

References
1. Semrud-Clikeman M. Social competence in children. Michigan: Springer
Science; 2007.
2. Spitzberg BH. Methods of interpersonal skill assessment. In: Greene JO,
Burleson BR, editors. Handbook of communication and social interaction
skills. Mahwah: Lawrence Erlbaum Associates; 2003. p. 93–113.
3. Jones DE, Greenberg M, Crowley M. Early social-emotional functioning
and public health: the relationship between kindergarten social competence and future wellness. Am J Public Health. 2015;105(11):2283–90.
4. O’Neill HF Jr, Allred K, Baker EL. Review of workforce readiness theoreticalframeworks. In: O’Neill Jr HF, editor. Workforce readiness: competencies
and assessment. Mahwah: Lawrence Erlbaum Associates; 1997. p. 3–26.
5. Brownell CA, Zerwas S, Ramani GB. “So big”: the development of bodyself-awareness in toddlers. Child Dev. 2007;78:1426–40.
6. Warneken F, Tomasello M. Altruistic helping in human infants and young
chimpanzees. Science. 2006;311:1301.
7. Warneken F, Chen F, Tomasello M. Cooperative activities in young children and chimpanzees. Child Dev. 2006;77:640–63.
8. Moore C. Understanding self and others in the second year. In: Brownwell
CA, Kopp CB, editors. Socioemotional development in the toddler years:transitions and transformations. New York: Guilford Press; 2007. p. 43–65.
9. Ereky-Stevens K. Associations between mothers’ sensitivity to their infants’internal states and children’s later understanding of mind and emotion.
Infant Child Dev. 2008;17:527–43.
10. Perren S, Alsaker FD. Depressive symptoms from kindergarten to earlyschool age: longitudinal associations with social skills deficits and peer
victimization. Child Adolesc Psychiatry Ment Health. 2009;3(1):28.
11. Cole DA, Martin JM, Powers B, Truglio R. Modeling causal relations
between academic and social competence and depression: a multitrait-multimethod longitudinal study of children. J Abnorm Psychol.
1996;105(2):258–70.
12. Henricsson L, Rydell AM. Children with behaviour problems: the influence of social competence and social relations on problem stability,
school achievement and peer acceptance across the first six years ofschool. Infant Child Dev. 2006;15(4):347–66.

Tomisaki et al. Child Adolesc Psychiatry Ment Health(2018) 12:53

13. Everson CA. Sustained sleep deprivation impairs host defense. Am J
Physiol. 1993;265:R1148–54.
14. Zee PC, Turek FW. Introduction to sleep and circadian rhythms. In:
Turek FW, Zee PC, editors. Regulation of sleep and circadian rhythms.
New York: Marcel Dekker, Inc.; 1999. p. 1–17.
15. Dahl RE. The development and disorders of sleep. Adv Pediatr.
1998;45:73–90.
16. Walker MP, Helm VDE. Overnight therapy? The role of sleep in emotional brain processing. Psychol Bull. 2009;135(5):731–48.
17. Walker MP. Sleep, memory and emotion. Prog Brain Res.
2010;185:49–68.
18. Lee KA, Landis C, Chasens ER, Dowling G, Merritt S, Parker KP, et al.
Sleep and chronobiology: recommendations for nursing education.
Nurs Outlook. 2005;52(3):126–33.
19. Gregory AM, O’Connor TG. Sleep problems in childhood: a longitudinal study of developmental change and association with behavioral
problems. J Am Acad Child Adolesc Psychiatry. 2002;41(8):964–71.
20. Dahl RE. The impact of inadequate sleep on children’s daytime cognitive function. Semin Pediatr Neurol. 1996;3:44–50.
21. Touchette E, Petit D, Tremblay RE, Montplaisir JY. Risk factors andconsequences of early childhood dyssomnias: new perspectives. Sleep
Med Rev. 2009;13(5):355–61.
22. Yokomaku A, Misao K, Omoto F, Yamagishi R, Tanaka K, Takada K, et al.
A study of the association between sleeping habit and problematic
behaviors in preschool children. Chronobiol Int. 2008;25(4):549–64.
23. Sadeh A, Marcas GD, Guri Y, Berger A, Tikotzky L, Bar-Haim Y. Infant
sleep predicts attention regulation and behavior problems at 3–4 yearsof age. Dev Neuropsychol. 2015;40(3):122–37.
24. Hall WA, Scher A, Zaidman-Zait A, Espezel H, Warnock F. A communitybased study of sleep and behavior problems in 12- to 36-month-old
children. Child Care Health Dev. 2012;38(3):379–89.
25. Vaughn BE, Elmore-Staton L, Shin N, El-Sheikh M. Sleep as a support
for social competence, peer relations, and cognitive functioning inpreschool children. Behav Sleep Med. 2015;13(2):92–106.
26. Schumacher AM, Miller AL, Watamura SE, Kurth S, Lassonde JM,
LeBourgeois MK. Sleep moderates the association between response
inhibition and self-regulation in early childhood. J Clin Child Adolesc
Psychol. 2017;46(2):222–35.
27. Bordeleau S, Bernier A, Carrier J. Maternal sensitivity and children’s
behavior problems: examining the moderating role of infant sleep
duration. J Clin Child Adolesc Psychol. 2012;41(4):471–81.
28. Randler C. Association between morningness–eveningness andmental and physical health in adolescents. Psychol Health Med.
2011;16(1):29–38.
29. Caci H, Mattei V, Bayle FJ, Nadalet L, Dossios C, Robert P, et al. Impulsivity but not venturesomeness is related to morningness. Psychiatry Res.
2005;134:259–65.
30. Carney CE, Edinger JD, Meyer B, Lindman L, Istre T. Daily activities andsleep quality in college students. Chronobiol Int. 2006;2006(23):623–37.
31. Gau SS, Soong WT, Merikangas KR. Correlates of sleep–wake patterns
among children and young adolescents in Taiwan. Sleep. 2004;27:512–9.
32. Gau SS, Shang CY, Merikangas KR, Chiu YN, Soong WT, Cheng AT. Association between morningness–eveningness and behavioral/emotional
problems among adolescents. J Biol Rhythms. 2007;22:268–74.
33. Gaina A, Sekine M, Kanayama H, Takashi Y, Hu L, Sengoku K, et al. Morning
evening preference: sleep pattern spectrum and lifestyle habits among
Japanese junior high school pupils. Chronobiol Int. 2006;23:607–21.
34. Monk TH, Buysse DJ, Potts JM, DeGrazia JM, Kupfer DJ. Morningness–eveningness and lifestyle regularity. Chronobiol Int. 2004;21:435–43.
35. Soehner AM, Kennedy KS, Monk TH. Personality correlates with sleep–
wake variables. Chronobiol Int. 2007;24:889–903.
36. Giannotti F, Cortesi F, Sebastian T, Ottaviano S. Circadian preference, sleep
and daytime behaviour in adolescence. J Sleep Res. 2002;11(3):191–9.
37. Susman EJ, Dockray S, Schiefelbein VL, Herwehe S, Heaton JA, Dorn LD.
Morningness/eveningness, morning-to-afternoon cortisol ratio, and antisocial behavior problems during puberty. Dev Psychol. 2007;43:811–22.
38. Mindell JA, Leichman ES, Dumond C, Sadeh A. Sleep and social-emotional development in infants and toddlers. J Clin Child Adolesc Psychol.
2017;46(2):236–46.

Page 10 of 11

39. Fukuda K. Education and sleeping problem. In: Takahashi K, editor. Somnology—sleeping science, medical, and sociology. Tokyo: Jihou; 2003. p.
169–83 (in Japanese).
40. Harada T. Evening-typed diurnal rhythm in Japanese children and theirmental health. J Child Health. 2004;63:202–9 (in Japanese).
41. Araki A, Ohinata J, Suzuki N, Iwasa S, Amamiya S, Tanaka H, et al. Questionnaire survey on sleep habits of 3-year-old children in Asahikawa city.
Off J Jpn Soc Child Neurol. 2008;40:370–4 (in Japanese).
42. Nakayama M, Hiraiwa M. A follow-up study of development in infants
through four months, 12 months, and 20 months of age: An analysis
concerning sleep–wake patterns. J Child Health. 2005;64(2):46–53 (inJapanese).
43. Touchette E, Petit D, Séguin JR, Boivin M, Tremblay RE, Montplaisir JY.
Associations between sleep duration patterns and behavioral/cognitive
functioning at school entry. Sleep. 2007;30(9):1213–9.
44. Spruyt K, Aitken RJ, So K, Charlton M, Adamson TM, Horne RS. Relationship between sleep/wake patterns, temperament and overall
development in term infants over the first year of life. Early Hum Dev.
2008;84(5):289–96.
45. Hysing M, Sivertsen B, Garthus-Niegel S, Eberhard-Gran M. Pediatric sleep
problems and social-emotional problems. A population-based study.
Infant Behav. 2016;42:111–8.
46. Sivertsen B, Harvey AG, Reichborn-Kjennerud T, Torgersen L, YstromE, et al. Later emotional and behavioral problems associated withsleep problems in toddlers: a longitudinal study. JAMA Pediatr.
2015;169(6):575–82.
47. Mindell JA, Sadeh A, Wiegand B, How TH, Goh DY. Cross-cultural differences in infant and toddler sleep. Sleep Med. 2010;11(3):274–80.
48. Kohyama J, Shiiki T, Ohinata-Sugimoto J, Hasegawa T. Potentially harmful
sleeping habits of 3-year-old children in Japan. J Dev Behav Pediatr.
2002;23:67–70.
49. Kawai H. Investigation on the health of young children in 2000. J Child
Health. 2001;60:543–87 (in Japanese).
50. Kohyama J, Shiiki T, Hasegawa T. Sleep duration of young children isaffected by nocturnal sleep onset time. Pediatr Int. 2000;42(5):589–91.
51. Touchette E, Mongrain V, Petit D, Tremblay RE, Montplaisir JY. Development of sleep–wake schedules during childhood and relationships withsleep duration. Arch Pediatr Adolesc Med. 2008;162:343–9.
52. Iwasaki M, Iemura A, Oyama T, Matsuishi T. A novel subjective sleep
assessment tool for healthy elementary school children in Japan. J Epidemiol. 2010;20:S476–81.
53. Iwasaki M, Iwata S, Iemura A, Yamashita N, Tomino Y, Anme T, et al. Utilityof subjective sleep assessment tools for healthy preschool children: acomparative study between sleep logs, questionnaires, and actigraphy. J
Epidemiol. 2010;20(2):143–9.
54. Caldwell BM, Bradley RH. Home observation for measurement of theenvironment. Little Rock: University of Arkansas; 1984.
55. Anme T. An evaluation of environmental stimulation and health andwelfare support system. J Ntl Rehab Center Disabl. 1991;12(1):29–36.
56. Anme T. Evaluation for child care environment. Tokyo: Kawasima Pubication; 1996.
57. Anme T. Evaluation of child care environment for 18-month child. Nippon
Koshu Eisei Zasshi. 1997;44(5):346–52.
58. Anme T, Yato Y, Shinohara R, Sugisawa Y. The validity and reliabilityof the interaction rating scale (IRS): characteristics for children withbehavioral or environmental difficulties. Jpn J Hum Sci Health Soc Serv.
2007;14(24):23–31.
59. Shinohara R, Sugisawa Y, Anme T. Factors related to social competencedevelopment of eighteen-month-old toddlers: longitudinal perspective,
with emphasis on “praise” in the parenting of four- and nine-month-old
infants. Jpn J Hum Sci Health Soc Serv. 2010;16:31–42 (in Japanese).
60. Sugisawa Y, Shinohara R, Tong L, Tanaka E, Yato Y, et al. Reliability andvalidity of interaction rating scale as an index of social competence. Jpn J
Hum Sci Health Soc Serv. 2010;16:43–55 (in Japanese).
61. Nagin DS, Tremblay RE. Parental and early childhood predictors of persistent physical aggression in boys from kindergarten to high school. ArchGen Psychiatry. 2001;58(4):389–94.
62. Nagin DS. Analyzing developmental trajectories: a semiparametric,
group-based approach. Psychol Methods. 1999;4:139–57.
63. Jones BL, Nagin DS. Advances in group-based trajectory modeling andSAS procedure for estimating them. Sociol Method Res. 2007;35:542–71.

Tomisaki et al. Child Adolesc Psychiatry Ment Health(2018) 12:53

64. Little RJA, Rubin DB. Statistical analysis with missing data. New York:
Wiley; 1987.
65. Tong L, Shinohara R, Sugisawa Y, Tanaka E, Maruyama A, Sawada Y, et al.
Relationship of working mothers’ parenting style and consistency toearly childhood development: a longitudinal investigation. J Adv Nurs.
2009;24:2067–76.
66. Gershoff ET. Corporal punishment by parents and associated child behaviors and experiences: a meta-analytic and theoretical review. Psychol Bull.
2002;128(4):539–79.
67. Gershoff ET, Lansford JE, Sexton HR, Davis-Kean P, Sameroff AJ. Longitudinal links between spanking and children’s externalizing behaviors in anational sample of White, Black, Hispanic, and Asian American families.
Child Dev. 2012;83(3):838–43.
68. Grogan-Kaylor A. Corporal punishment and the growth trajectory ofchildren’s antisocial behavior. Child Maltreat. 2005;10:283–92.
69. Taguchi M, Sakurada S, Terazono S, Morino M, Nosaki H, Ootani T.
The interaction between child sleep and aggressiveness. Sci Health.
2006;48(3):225–9 (in Japanese).
70. Gregory AM, Van der Ende J, Willis TA, Verhulst FC. Parent-reported sleep
problems during development and self-reported anxiety/depression,
attention problems, and aggressive behavior later in life. Arch Pediatr
Adolesc Med. 2008;162(4):330–5.
71. Wang H, Sekine M, Chen X, Yamagami T, Kagamimori S. Lifestyle at
3 years of age and quality of life (QOL) in first-year junior high school
students in Japan: results of the Toyama Birth Cohort Study. Qual Life Res.
2008;17(2):257–65.

Page 11 of 11

72. Kohyama J, Mindell JA, Sadeh A. Sleep characteristics of young children in
Japan: internet study and comparison with other Asian countries. Pediatr
Int. 2011;53(5):649–55.
73. Iglowstein I, Jenni OG, Molinari L, Largo RH. Sleep duration from infancy
to adolescence: reference values and generational trends. Pediatrics.
2003;111(2):302–7.
74. Anme T. Manual of interaction rating scale. Tokyo: Nihon shouni iji shuppansha co, ltd.; 2009 (in Japanese).
75. Vandell DL, Wilson KS, Whalen WT. Birth-order and social-experience differences in infant–peer interaction. Dev Psychol. 1981;17:438–45.
76. Belsky J. Early human experience: a family perspective. Dev Psychol.
1981;17:3.
77. Cowen EL, Lotyczewski BS, Weissberg RP. Risk and resource indicatorsand their relationship to young children’s school adjustment. Am J Community Psychol. 1984;12:353–67.
78. Gresham FM, Elliott SN. Assessment and classification of children’ssocial skills: a review of methods and issues. School Psychol Rev.
1984;13:292–301.
79. Anme T, Sugisawa Y, Shinohara R, Matsumoto M, Watanabe T, Tokutake K,
et al. Validity and reliability of the Interaction Rating Scale between Children (IRSC) by using motion capture analysis of head movement. Public
Health Res. 2012;2(6):208–12.

Ready to submit your research ? Choose BMC and benefit from:• fast, convenient online submission• thorough peer review by experienced researchers in your field• rapid publication on acceptance• support for research data, including large and complex data types• gold Open Access which fosters wider collaboration and increased citations• maximum visibility for your research: over 100M website views per year
At BMC, research is always in progress.
Learn more biomedcentral.com/submissions