Table 2.

Hierarchical multiple regression analyses for RRB Subtype (RBS-R) predicting socialization domain scores (VABS-II) at 24 and 36 months

	Model 1		Model 2		Model 3		Model 4
24 Months
Sex	− 1.145		.745		.563		.677
IQ	.095		.085		.125		.130
RSM			− 5.081***		− 2.463		− 2.331
IS					− 3.213		− 2.900
SIB							− .607
F	.838		8.342***		7.246***		5.743***
$R^2$	.027		.298		.333		.335
Δ$R^2$			.271***		.035		.002
36 Months
Sex	4.340		5.515		5.453		7.341
IQ	.336***		.227**		.224**		.216**
RSM			− 6.312***		− 6.723**		− 5.710*
IS					.501		.356
SIB							− 2.139
F	7.693**		15.191***		11.058***		9.430***
$R^2$	.325		.595		.596		.619
Δ $R^2$			.270***		.000		.023

Standardized regression coefficients. 24 months (N = 63). 36 months (N = 35). Bold face indicates Δ $R^2$ that survive the Bonferroni adjusted alpha level ($\alpha$ = .008)

RRB restricted repetitive behavior, RBS-R Repetitive Behavior Scale-Revised, VABS-II Vineland Adaptive Behavior Scale, IS insistence on sameness, RSM repetitive sensory motor, SIB self-injurious behavior, IQ Mullen early learning composite

*p < .05. **p < .01. ***p < .001