Table 1. Demographic information and children’s scores on the IRS.

Items		categries	Total Score on the IRS (0–25 points)		High Scoring Group (18–25 points)		Low Scoring Group (0–17 points)
			n	%	n	%	n	%
Gender	Boys	1	125	50.8	107	48.4	18	72.0
	Girls	2	121	49.2	114	51.6	7	28.0
Siblings	No	1	137	55.7	121	54.8	16	64.0
	Yes	2	109	44.3	100	45.3	9	36.0
Family type	Nuclear family	1	217	88.2	195	88.2	22	88.0
	Extended family	2	29	11.8	26	11.8	3	12.0
Mother’s age	20–29	1	60	24.4	56	25.3	4	16.0
	30–39	2	174	70.7	156	70.6	18	72.0
	40–	3	12	4.9	9	4.1	3	12.0
Mother’s education	Intermediate school	1	3	1.2	3	1.4	0	0.0
	High school	2	49	19.9	45	20.4	4	16.0
	Technical college	3	50	20.3	43	19.5	7	28.0
	Junior college	4	71	28.9	68	30.8	3	12.0
	University	5	72	29.3	61	27.6	11	44.0
	Graduate	6	1	0.4	1	0.5	0	0.0
Mother’s occupation	No	1	123	50.0	112	50.7	11	44.0
	Yes	2	123	50.0	109	49.3	14	56.0
Father’s age	20–29	1	46	18.7	43	19.5	3	12.0
	30–39	2	169	68.7	152	68.8	17	68.0
	40–49	3	27	11.0	23	10.4	4	16.0
	50–	4	4	1.6	3	1.4	1	4.0
Father’s education	Intermediate school	1	4	1.6	4	1.8	0	0.0
	High school	2	81	32.9	71	32.1	10	40.0
	Technical college	3	36	14.6	33	14.9	3	12.0
	Junior college	4	6	2.4	6	2.7	0	0.0
	University	5	104	42.3	93	42.1	11	44.0
	Graduate	6	15	6.1	14	6.3	1	4.0
Family’s economic status ​ (annual income)	<2 million JPY	1	7	2.9	5	2.3	2	8.0
	2–4 million JPY	2	60	24.4	53	24.0	7	28.0
	4–6 million JPY	3	120	48.8	109	49.3	11	44.0
	6–8 million JPY	4	34	13.8	30	13.6	4	16.0
	8–10 million JPY	5	14	5.7	13	5.9	1	4.0
	≧10 million JPY	6	11	4.5	11	5.0	0	0.0

N = 246.