The peak latencies of the responses were determined from the deviant/novel-standard difference signals from channel F3, which was deemed to be a representative of the response for all four channels included in the analysis. For the deviant tones, the peak latency for the MMN was defined as the latency of the largest negativity between 200 and 300 ms, for the P3a as the latency of the largest positivity between 200 and 300 ms, and for the LDN as

the latency of the largest negativity between 500 and 600 ms after the deviant became physically PD0325901 concentration distinct from the standard. For the novel sounds, in turn, the peak latency of the P3a was determined as the latency of the largest positivity between 200 and 300 ms and for the LDN/RON as the latency of the largest negativity between 600 and 700 ms. For the analysis of the MMN and P3a, mean amplitudes of the responses were calculated on channels F3, F4, C3 and C4 over 50 ms time windows centred on the peak latencies. These values were then averaged together separately for each response and the

average value was used CH5424802 nmr for testing the significance of the response and for the correlation analyses. An identical procedure was used for the LDN and novelty P3a except that a 100 ms time window was used in the analyses as these responses spanned a longer time period than the MMN and the P3a elicited by the deviant tones. To test the statistical significance of the MMN, P3a and the LDN for a given deviant, the mean amplitudes were compared with zero with a two-tailed one-sample t-test. Pearson’s correlation coefficients between the overall musical behaviour score and the MMN, P3a, and LDN amplitudes were calculated. Partial correlations between the response amplitudes and the overall musical activities at home score were also calculated to control for various external factors. These factors included Wilson disease protein the child’s age, gender, and socioeconomic status. The socioeconomic status

measure included the income and education of both parents measured on six-step scales (income scale: 1, under 1000 Euros/month; 2, 1000–2000 Euros/month; 3, 2000–3000 Euros/month; 4, 3000–4000 Euros/month; 5, 4000–5000 Euros/month; 6, over 5000 Euros/month; education scale: 1, comprehensive school; 2, upper secondary school or vocational school; 3, a higher degree than upper secondary school or vocational school that is not a bachelor’s, master’s, licenciate, or doctoral degree; 4, bachelor’s degree or equivalent; 5, master’s degree or equivalent; 6, licenciate or doctoral level degree). The answers of both parents to these questions (i.e. number from one to six) were added together to form a composite socioeconomic status score for the parents of each child. Exposure to recorded music at home was not included in the musical activities index because it was expected that the more active and interactive musical behaviours would be more likely to be associated with auditory development in 2–3-year-olds (cf. Gerry et al., 2012).