Table 2.

Main Effects of Subject Group, Stimulus Type and Hemisphere.

Main Effects of Subject Group:
Component	F(1,38)	p value	Driven By
P400 Latency	4.16	0.048	Faster responses in High-Risk than Low-Risk infants1
Nc Amplitude	4.69	0.037	Larger negative responses in Low-Risk than High-Risk infants2

Main Effects of Stimulus Type:
Component	F(1,38)	p value	Driven By
N290 Latency	8.63	0.006	Faster responses to Objects than Faces1
N290 Amplitude	5.12	0.030	Larger negative responses to Faces than Objects3
P400 Amplitude	6.69	0.014	Larger positive responses to Objects than Faces4
Nc Amplitude	8.69	0.005	Larger negative responses to Objects than Faces5

Main Effects of Hemisphere:
Component	F(1,38)	p value	Driven By
P100 Amplitude	5.27	0.027	Larger positive responses in Left than Right hemisphere6
N290 Amplitude	8.32	0.006	Larger negative responses in Right than Left hemisphere6
P400 Amplitude	7.57	0.009	Larger positive responses in Left than Right hemisphere6

¹The interpretation of this main effect is modified by the subject group × stimulus type interaction, see Results.

²This effect, which does not interact with stimulus type, indicates that Low-Risk infants may have allocated more overall attention than High-Risk infants.

³This result mirrors that seen in previous ERP studies of typical infants (30).

⁴This result, although somewhat surprising, is similar to the non-face advantage for the P400 previously reported in ERP studies of typical infants (30).

⁵The Nc is generally believed to be tied to salience/attention (which is thought to differ between familiar and unfamiliar stimuli), not face vs. object processing per se (see 33). However, note that the current study did not find familiarity effects for the Nc (in either Low- or High-Risk infants), which could be because our familiar vs. unfamiliar stimuli did not differ sufficiently in salience (see 33 for discussion). Also, note that the current study found no interactions between familiarity and subject group, which is not consistent with results from previous neural imaging studies that reported differences in the response to familiar vs. unfamiliar faces between individuals with ASD and typical controls (ERPs: 81, fMRI: 99). Again, the null finding of the current study could result if our familiar vs. unfamiliar stimuli did not differ sufficiently in salience. Other reasons for a discrepancy between the current and previous studies include different ages (infants vs. children) and different diagnostic categories (High-Risk infants vs. individuals diagnosed with ASD) across studies.

⁶The interpretation of this main effect is modified by the subject group × hemisphere interaction, see Results.