Cognitive interference and aging: Insights from a spatial stimulus–response consistency task One ´simo Juncos-Rabada ´n a, * , Arturo X. Pereiro b , David Facal a a Department of Developmental and Educational Psychology, University of Santiago de Compostela, Campus Sur, 15782 Santiago de Compostela, Spain b Department of Developmental and Educational Psychology, University of Almeria, Spain Received 24 July 2006; received in revised form 13 May 2007; accepted 15 May 2007 Available online 28 June 2007 Abstract One hundred and thirty-one adults belonging to four age groups (19–26, 50–59, 60–69 and 70–82 years) performed a spatial stimulus– response consistency task in which the response dimension (left or right) overlapped relevant and irrelevant stimulus dimensions. The influence of the irrelevant stimulus dimension on response time was significantly greater in the middle age groups than among 19–26 year-olds, and significantly greater in the highest age group than in any other. This pattern persisted when allowance was made for a significant age-related increase in processing time (measured as reaction time in a single-stimulus, single-response task). It is concluded that in tasks of the kind used, the elderly resist interference from the irrelevant information less easily than do younger persons. Inter- estingly, comparison of Vincentized quintiles suggested that the effect of the irrelevant stimulus dimension decreased with increasing response time among 19–26 year-olds, but increased with response time among 70–82 year-olds. Ó 2007 Elsevier B.V. All rights reserved. PsycINFO classification: 2860; 2300 Keywords: Stimulus–response consistency; Simon effect; Aging; Inhibition; Interference; Processing speed 1. Introduction One of the most plausible mechanisms hypothesized to account for certain aspects of cognitive decline in aging is that an age-related deficit in inhibitory control prevents sup- pression of exogenously or endogenously generated infor- mation flows that are irrelevant to and interfere with the task in hand (Hasher & Zacks, 1988; Shimamura & Jurica, 1994; Tun, O’Kane, & Wingfield, 2002; Zacks & Hasher, 1997). However, not all experiments designed to investigate such an effect have in fact consistently detected inhibition deficits among elderly persons; such is the case of negative priming and the Stroop task (Verhaeghen & Cerella, 2002; Verhaeghen & De Meersman, 1998a, 1998b). As a result, some authors have concluded that age-related cognitive decline may be due to an age-related reduction in cognitive processing speed rather than to deficient inhibition (Salt- house & Meinz, 1995; Salthouse, Toth, Hancock, & Woo- dard, 1997; Verhaeghen & De Meersman, 1998a, 1998b). In the study described here, we took processing speed into account in using a spatial stimulus–response consistency task (a variant of the usual Simon task) to investigate the influence of age on interference from irrelevant information. 1.1. Spatial stimulus–response consistency effects Simon and Rudell (1967) discovered that when subjects controlling two response keys were instructed to press the right-hand key upon hearing the word ‘‘right’’ and the left-hand key upon hearing the word ‘‘left’’, their response times were significantly shorter if ‘‘left’’ was heard by the 0001-6918/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.actpsy.2007.05.003 * Corresponding author. Tel.: +34 981563100; fax: +34 981528071. E-mail address: pejuncos@usc.es (O. Juncos-Rabada ´n). www.elsevier.com/locate/actpsy Available online at www.sciencedirect.com Acta Psychologica 127 (2008) 237–246