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The subjects as a simple random effect fallacy: subject variability and morphological family effects in the mental
R Harald Baayen1, Fiona J Tweedie, Robert Schreuder
1Interfaculty Research Unit for Language and Speech, Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands. baayen@mpi.nl
Abstract:
This is a methodological study addressing the appropriateness of standard by-subject and by-item averaging procedures for the analysis of repeated-measures designs. By means of a reanalysis of published data (Schreuder & Baayen, 1997), using random regression models, we present a proof of existence of systematic variability between participants that is ignored in the standard psycholinguistic analytical procedures. By applying linear mixed effects modeling (Pinheiro & Bates, 2000), we call attention to the potential lack of power of the by-subject and by-item analyses, which in this case study fail to reveal the coexistence of a facilitatory family size effect and an inhibitory family frequency effect in visual and auditory lexical processing.