Variability in the semantic errors produced by brain-injured patients

One of the most common types of errors produced by aphasic patients during oral word production is semantic errors. However, although aphasia semantic errors are often treated as a single homogenous group, there are, in fact, several subtypes defined by the nature of the error-target relationship: paradigmatic, if the two words are category coordinates; syntagmatic, if they are associatively related but from different semantic categories; and superordinate, if the meaning of the error is broader than the meaning of the target. The goal of this study was to investigate whether or not these various subtypes of semantic errors have a similar processing origin. With this objective, we compared the patterns of semantic errors made by a group of Alzheimer patients in a picture-naming task with those made by a group of aphasic patients. We examined the percentages of the different error types, the degree of association between target and error, and the frequency values both of errors and targets. The results suggest that the three subtypes of semantic errors have different origins: the superordinate appear to arise at the semantic level, the syntagmatic at the lexical level, and the paradigmatic at both levels of processing.