No Category Specificity in Alzheimer’s Disease: A Normal Aging Effect F. Javier Moreno-Martı ´nez Universidad Nacional de Educacio´n a Distancia, Madrid, Spain Keith R. Laws University of Hertfordshire, United Kingdom The authors examined category effects on tasks of picture naming, naming to definition, and word– picture matching in 38 patients with Alzheimer’s disease (AD) and 30 elderly controls. Each task was matched across category on all “nuisance” variables known to differ across domains. Standard analyses revealed significant category disadvantages for classifying living things in AD patients but also for elderly controls on each task. To overcome the ceiling effect in controls, the authors conducted 1,000 bootstrap analyses of covariance, with control performance as a difficulty index covariate. These covariate analyses eliminated the category effect in AD patients on all 3 tasks. Indeed, the authors report that control performance accounted for 64% (picture naming), 49% (naming to description), and 42% (word–picture matching) of variance in AD performance. This suggests that, although category effects in AD patients do not reflect intrinsic variables, the size and direction of the category effect are not different from those in elderly controls. Keywords: semantic memory, category specificity, nuisance variables, bootstrap analysis The study of patients with pathologies that affect semantic memory indicates that some categories of conceptual knowledge may be differentially affected. The more typical pattern (Laws, Crawford, Gnoato, & Sartori, 2007) is an impairment of identify- ing living things (e.g., animals, fruits, and vegetables), sparing nonliving things (e.g., tools, furniture, and vehicles). The opposite pattern has been reported but far fewer times, and according to Laws (2005), the ratio of living to nonliving naming disorders is 5 to 1. Most studies of categorical impairment have been case studies of patients with pathologies such as herpes simplex encephalitis, strokes, or head injuries; however, patients with Alzheimer’s dis- ease (AD) provide an opportunity to study larger samples of patients with known semantic difficulties. In spite of the wide- spread demonstration of semantic impairment in AD (e.g., Bayles & Tomoeda, 1983; Martin & Fedio, 1983; Salmon, Butters, & Chan, 1999), the issue of categorical impairment is still much debated among researchers. One of the first studies that reported category specificity deficits in AD for naming pictures of living things was carried out by Silveri, Daniele, Giustolisi, and Gainotti (1991). Tippett, Gross- man, and Farah (1996) later replicated and expanded on Silveri et al.’s findings by showing that the disproportionate deficit with living things disappeared once the items were controlled for fa- miliarity, lexical frequency, and visual complexity (which all favored nonliving things). Tippett et al. thereby concluded that Silveri et al.’s findings spuriously resulted from a lack of control of “nuisance” variables (Funnell & Sheridan, 1992; Stewart, Par- kin, & Hunkin, 1992). Some lack of consistency has been a constant in the literature on category specificity deficits in AD. In fact, some studies have found a specific impairment with living things (Montanes, Goldblum, & Boller, 1995; Silveri et al., 1991), others have not found category effects (Hodges, Salmon, & But- ters, 1992; Tippett et al., 1996), and finally, some of them have reported impairment both with living and nonliving things (with respect to each other) in the same sample of patients (Laws, Gale, Leeson, & Crawford, 2005; Moreno-Martı ´nez, Tallo´ n-Barranco, & Frank-Garcı ´a, 2007; Tippett, Meier, Blackwood, & Diaz-Asper, 2007). However, as with other pathologies, reports of specific impairment with nonliving things are rare. Because most of the group studies in AD patients have docu- mented an impairment with living things, it seems plausible that this result may reflect the lack of control over nuisance variables in some studies. Nonetheless, as the opposite pattern has been re- ported, this appears to mitigate against providing a complete explanation of the category specificity effects. Nevertheless, a recent meta-analysis of 21 studies including over 500 AD patients and 500 healthy control patients surprisingly revealed that the impression of a greater incidence of deficits with living things in AD patients may be misleading (Laws, Adlington, Gale, Moreno- Martı ´nez and Sartori, 2007). Although Laws, Adlington et al. (2007) found more reports of living-thing deficits, these were, in fact, no larger than the loss associated with naming nonliving items. Hence, the lack of a significant difference in the effect sizes for naming pictures of living and nonliving things in AD patients suggests that the evidence for category effects in AD patients is less certain than might seem. As a common practice, many group studies in AD have esti- mated categorical impairment by using exclusively— or almost exclusively—the picture-naming task (for a meta-analytic review, see Laws, Adlington et al., 2007). Anomia is one of the first markers in AD (Bowles, Obler, & Albert, 1987; Gainotti, Daniele, Nocentini, & Silveri, 1989; Hodges, Patterson, Graham, & Daw- F. Javier Moreno-Martı ´nez, Departamento de Psicologı ´a Ba´sica I, Uni- versidad Nacional de Educacio´ n a Distancia, Madrid, Spain; Keith R Laws, School of Psychology, University of Hertfordshire, United Kingdom. This study was supported by a postdoctoral fellowship from the program Jose´ Castillejo (JC2007-00248) from the Ministerio de Educacio´n y Cien- cia to F. Javier Moreno-Martı ´nez. We thank Sara Can˜amo´n, Larry Seid- man, and the two anonymous reviewers whose comments helped very much to improve an earlier version of the article. Correspondence concerning this article should be addressed to F. Javier Moreno-Martı ´nez, Universidad Nacional de Educacio´ n a Distancia, Depar- tamento de Psicologı ´a Ba´sica I, C/ Juan del Rosal, No. 10, 28040, Madrid, Spain. E-mail: fjmoreno@psi.uned.es Neuropsychology Copyright 2008 by the American Psychological Association 2008, Vol. 22, No. 4, 485– 490 0894-4105/08/$12.00 DOI: 10.1037/0894-4105.22.4.485 485 This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.