Atypical auditory ERPs in SLI 583 Figure 4 2-D cartoons showing brain responses to syllables in time window 48 to 328 ms for typically developing and SLI subgroups, subdivided according to ICC for speech at C4. As can be seen in Figure 4, brainmaps for the SLI group with average ICC are closely similar to the typically developing group. Conﬁrming the picture from Figure 3, the grand average for the SLI subgroups with low ICC are markedly different, with a pronounced early negativ- ity starting around 100 ms at right central sites. In the receptive SLI subgroup this spreads to encompass a wide fronto-central region in the next time slice, at a point when other groups are only beginning to develop signs of negativity in these regions. Another unusual feature in the low-ICC receptive SLI subgroup is bilat- eral positivity in temporal regions around 132 ms, at a time when other groups show positivity lateralized to right temporal electrodes. Analogous brainmaps were also derived for ERPs to tone stimuli for the same subgroups (see Supplementary material on http://www.psy.ox.ac.uk/ oscci/dbhtml/Excel%20ﬁles/supplementary%20plots.xls), and again showed anomalous right central negativity around 100 ms in the low-ICC receptive SLI subgroup. © 2007 The Authors. Journal compilation © 2007 Blackwell Publishing Ltd. Discussion Using a sample of children aged from 5 to 10 years, we compared each individual’s waveform in the range 100 to 228 ms with that of a normative grand average. The analytic method was based on Bishop and McArthur (2005): rather than attempting to measure the amplitude and latency of peaks, we used the ICC to provide a global measure of similarity between the waveform of an individual child and the grand average of a typically developing group of the same age. We found that the waveforms of children with SLI showed abnormalities (i.e. relatively low ICCs) for frontal, central and tem- poral electrodes on the right side of the head, with a trend for smaller differences at the midline. No differences were seen for electrodes on the left side of the head. The ﬁnding of signiﬁcant group differences in the time win- dow 100–228 ms is consistent with results obtained with older children by Bishop and McArthur (2005), although