Table 4.

Predictive effects of speech preference, risk group, and the interaction of speech preference and risk group on social development in Experiment 1 (speech vs. non-speech; top) and Experiment 2 (speech vs. monkey calls; bottom).

	Exp. 1: Speech vs. Non-Speech
	Total Score				Total Markers
	R2Δ	B	SE	95 % CI	R2Δ	B	SE	95 % CI
Step 1
Constant	.04*	5.09	0.39	[4.33, 5.86]	.03†	3.46	0.23	[3.01, 3.91]
SPI		−0.14	0.07	[−0.27, 0.00]		−0.07	0.04	[−0.15, 0.01]
Step 2
Constant	.04*	4.50	0.49	[3.53, 5.47]	.04*	3.11	0.29	[2.54, 3.68]
SPI		−0.13	0.07	[−0.27, 0.00]		−0.07	0.04	[−0.14, 0.01]
Risk Group		1.50	0.78	[−0.05, 3.04]		0.88	0.46	[−0.03, 1.78]
Constant	.02*	4.49	0.49	[3.53, 5.46]	.03*	3.11	0.28	[2.54, 3.67]
SPI		−0.04	0.09	[−0.22, 0.14]		0.00	0.05	[−0.11, 0.11]
Risk Group		1.49	0.77	[−0.05, 3.03]		0.87	0.45	[−0.03, 1.77]
SPI * Risk Group Interaction	−0.19	0.13	[−0.45, 0.07]		−0.13	0.08	90.28, 0.02]
	Exp. 2: Speech vs. Monkey Calls
	Total Score				Total Markers
	R2Δ	B	SE	95 % CI	R2Δ	B	SE	95 % CI
Step 1
Constant	.00	5.34	0.41	[4.52, 6.16]	.00	3.51	0.24	[3.03, 3.98]
SPI		−0.03	0.06	[−0.15, 0.09]		−0.02	0.04	[−0.09, 0.05]
Step 2
Constant	.02	4.86	0.56	[3.74, 5.97]	.02	3.19	0.32	[2.55, 3.84]
SPI				[−0.16, 0.08]		−0.02	0.04	[−0.09, 0.05]
Risk Group		−0.04	0.06	[−0.60, 2.70]		0.68	0.48	[−0.27, 1.64]
Step 3		1.05	0.83
Constant	.04	4.95	0.55	[3.85,	.05†	3.25	0.32	[2.62,
				6.05]				3.89]
SPI		0.09	0.08	[−0.08, 0.25]		0.05	0.05	[−0.04, 0.15]
Risk Group		1.02	0.82	[−0.60, 2.64]		0.66	0.47	[−0.27, 1.60]
SPI * Risk Group Interaction	−0.24	0.12	[−0.48, −0.01]		−0.16	0.07	[−0.29, −0.02]

^***p < .001.

^**p < .01.

^*p < .05.

^†p < .10.