a1 Social, Life, and Engineering Sciences Imaging Center, The Pennsylvania State University, University Park, USA
a2 Biological Psychology, VU University Amsterdam, The Netherlands
a3 Neuroscience Campus Amsterdam, VU University Amsterdam, The Netherlands
a4 Department of Psychology, University of Virginia, Charlottesville, USA
A new genetic factor model for multivariate phenotypic time series, iFACE, is presented which allows for the estimation of subject-specific model parameters of genetic and environmental factors. The iFACE was applied to multivariate EEG registrations obtained with single dizygotic twin pairs. The results showed evidence for considerable subject-specificity in heritabilities and environmental effects. The assumption that the population is homogeneous (i.e., that each case in the population obeys the same parametric model), does not hold for these psychophysiological data, and its use should be critically reconsidered. We conclude that the iFACE provides a powerful new methodology to assess heterogeneity (subject-specificity) based on phenotypic observations.
(Received November 17 2011)
(Accepted March 20 2012)