Neural Correlates of Processing Syntax in Music and ... - PubMan

Experiment III 127
cational background of the children. To control for the socio-economic background of
the children’s families, the occupation of the parents was first classified in terms of the
International Standard Classification of Occupation 1988 (ISCO88; International Labour
Organization, 1990). Then, the International Socio-Economic Index of Occupational
Status (ISEI; Ganzeboom & Treiman, 1996) was acquired as a transformation of
the ISCO88 codes. These values provide a measure of the status for a certain occupation
(e.g., the highest ISEI value in the sample was 90 [judge], the lowest was 16 [cleaner]).
Parents filled out a questionnaire (see Appendix) providing additional information on
the health status of the children, their educational background, their language acquisition,
their musical background, and other familial variables (e.g., number of siblings).
This information allowed to decide which children had to be excluded. Initially, it was
planned to use some of these variables (e.g. how long an instrument was learned) as
further predictors. However, for none variable, a reliable correlation with the electrophysiological
measures was found.
EEG recording and processing
EEG recording was identical to Experiment II. There were minor changes with regard to
the rejection criteria: the amplitude threshold (criterion [1] in Experiment I and II) was
lowered to ±100 μV; and the threshold for the linear trend (criterion [2]) was lowered to
±120 μV. 24 Non-rejected epochs were averaged (music: M = 69 trials [attentive part],
M = 81 trials [non-attentive part]; language: M = 62 trials [attentive part], M = 76 trials
[non-attentive part]). For the language experiment – that was not part of Experiment I
and II – a period of 0 to 1500 ms after stimulus onset was averaged with a baseline from
0 to 100 ms. These values were chosen in accordance with earlier experiments using the
same paradigms (e.g., Friederici et al., 1993; Hahne et al., 2004).
Statistical evaluation
It was not necessary to remove outliers in the data since all used variables did conform
to a standard normal distribution (with Kolmogorov-Smirnov tests; the probability of
deviating from a standard normal distribution was not significant: 0.25 ��p ���������edian
= 0.84). The values of the duration of education and the socio-economic status of
the parents as well as the verbal IQ values were compared by means of t-tests for independent
samples for each of the variables separately. The behavioural data (number of
correct responses and reaction times for the button-presses in response to a timbre
24 The different amplitude thresholds were chosen because the amplitudes of the EEG measurement differed
between the age groups (i.e., younger children usually show larger amplitudes in the EEG, presumably
due to a lower thickness of their skull).