Table 1.

Descriptions of primary variables at both individual and assessment levels

	High familial risk (n = 21)					Low familial risk (n = 21)
	n	$\overline{X}$	SD	min	max	n	$\overline{X}$	SD	min	max
Individual-level variables
n assessments	21	1.76	0.83	1	3	21	1.71	0.78	1	3
MSEL Early Learning Score	21	97.62	16.26	60	137	21	102.86	10.96	80	117
ADOS Severity Score	20	3.95	2.76	1	10	–	–	–	–	–
Assessment-level variables
Age in months	37	9.80	2.43	5.98	13.41	36	10.23	2.23	5.69	13.74
Proportion time inattentive	37	0.40	0.25	0.08	0.95	36	0.43	0.22	0.03	0.81
Proportion time in HRDSA	37	0.30	0.21	0.00	0.92	36	0.30	0.21	0.06	0.95
IBI change during HRDSA	34	33.38	23.53	3.96	110.47	36	36.02	22.52	3.56	130.15

Individual-level variables are measured on one occasion per individual, and assessment-level variables are collapsed across all assessments and individuals in each group

ADOS Autism Diagnostic Observation Schedule, HRDSA heart rate-defined sustained attention, IBI interbeat interval, MSEL Mullen Scales of Early Learning