Does resting electroencephalograph asymmetry reflect a trait? An application of latent state-trait theory.

Recent research on brain asymmetry and emotion treated measures of resting electroencephalograph (EEG) asymmetry as genuine trait variables, but inconsistency in reported findings and modest retest correlations of baseline asymmetry are not consistent with this practice. The present study examined the alternative hypothesis that resting EEG asymmetry represents a superimposition of a traitlike activation asymmetry with substantial state-dependent fluctuations. Resting EEG was collected from 59 participants on 4 occasions of measurement, and data were analyzed in terms of latent state-trait theory. For most scalp regions, about 60% of the variance of the asymmetry measure was due to individual differences on a temporally stable latent trait, and 40% of the variance was due to occasion-specific fluctuations, but measurement errors were negligible. Further analyses indicated that these fluctuations might be efficiently reduced by aggregation across several occasions.