Table 4. Pair Affiliation.

Summary of Multilevel Models with Treatment Effects on Home cage Pair mate Affiliation Across the First Four Months of Pairing. Subject ID nested within pair mate ID was included as a random effect in all models. To calculate p values for each estimate in Model 1, DF of 27 were used (29 subjects – 1 predictor – 1). To calculate the p value for each estimate in Model 2, DF of 25 were used (29 subjects – 3 predictors – 1). The Null AIC indicates the AIC of a model with the outcome variable predicted by only the intercept and random effects; for a full summary of the stepwise models tested, see Supplementary Table 1. * indicates p < .05.

	Null	Model 1					Model 2
	AIC	β	SE	t	p	AIC	β	SE	t	p	AIC
Proximity	309.5	-	-	-	-	301.1	-	-	-	-	293.9
Treatment	-	−0.42	0.12	−3.46	0.002*	-	−0.42	0.12	−3.46	0.002*	-
Month	-	-	-	-	-	-	0.22	0.07	3.40	0.002*	-
Treatment x Month	-	-	-	-	-	-	−0.02	0.07	−0.36	0.72	-
Contact	311.5	-	-	-	-	303.7	-	-	-	-	296
Treatment	-	−0.39	0.12	−3.36	0.002*	-	−0.40	0.11	−3.46	0.002*	-
Month	-	-	-	-	-	-	0.20	0.07	3.02	0.006*	-
Treatment x Month	-	-	-	-	-	-	0.12	0.07	1.74	0.09	-
Tail Twining	304.2	-	-	-	-	301.7	-	-	-	-	305.4
Treatment	-	0.30	0.14	2.12	0.043*	-	0.30	0.14	2.12	0.044*	-
Month	-	-	-	-	-	-	−0.02	0.07	−0.25	0.81	-
Treatment x Month	-	-	-	-	-	-	−0.03	0.07	−0.47	0.64	-