Structure versus processing deficits in Alzheimer's disease, a matter of degree: a comment on Storms et al. (2003)

G. Storms, T. Dirikx, J. Saerens, S. Verstraeten, and P. P. De Deyn (2003) argued that multidimensional scaling studies are ill-suited for investigating semantic deficits in individuals diagnosed with dementia of the Alzheimer type (DAT) because such individuals show great inter- and intraindividual variability in their proximity judgments. Discussed in this commentary are (a) the possible role of attentional set in producing inconsistent performance across trials, (b) the implications of attentional factors on the structure versus process debate, and (c) the inevitable semantic degradation following severe progression of the disease. A framework is presented for considering nonlinear performance differences as a function of attentional demands of the task, vulnerability of the semantic representation, and progression of the disease.