Attentional switching in the sequential flanker task: Age, location, and time course effects Karen Z.H. Li a, * , Kate Dupuis b a Department of Psychology, Concordia University, 7141 Sherbrooke St. West, Montre ´al, Que ´bec, Canada H4B 1R6 b Human Communication Laboratory, Department of Psychology, University of Toronto at Mississauga, Canada Received 15 February 2007; received in revised form 6 August 2007; accepted 8 August 2007 Available online 14 September 2007 Abstract The sequential flanker task was developed to study sequential performance using methodology borrowed from studies of task switch- ing. We investigated age differences in backward inhibition [BI: Mayr, U., & Keele, S. W. (2000). Changing internal constraints on action: The role of backward inhibition. Journal of Experimental Psychology: General, 129, 4–26] during a sequential category search task. Participants learned four animal categories in a fixed order, and then searched for exemplars from those categories in runs of mis-ordered exemplars. Across three experiments, we observed robust BI facilitation effects. However, the magnitude of BI effects did not differ across age groups. This age-invariance held despite manipulations of distractibility (Experiment 2), and interstimulus interval (Experiment 3), suggesting that BI processes may be relatively automatic and obligatory in the context of sequential tasks. The findings are discussed in terms of the attentional mechanisms that underlie task set switching and sequential performance. Crown Copyright Ó 2007 Published by Elsevier B.V. All rights reserved. PsycINFO classification: 2820 Keywords: Sequential performance; Inhibition; Executive control; Task set switching 1. Introduction Several areas of research converge to suggest that there may be an age-related decline in sequential performance, which is essential for many activities of daily living (e.g., bathing, cooking). Sequential performance, defined here as the completion of multiple steps in fixed order, may be supported by inhibitory mechanisms which prevent task repetitions and propel attention forward (e.g., Houghton & Tipper, 1996; Li, Lindenberger, Ru ¨ nger, & Frensch, 2000). Similarly, the rapid transition from one task set to the next during task set switching has been hypothesized to involve backward inhibition (BI: Mayr & Keele, 2000; see also Arbuthnott & Frank, 2000; Arbuthnott & Wood- ward, 2002; Hu ¨bner, Dreisbach, Haider, & Kluwe, 2003). By this view, BI suppresses features relevant to the previous task set when a switch has occurred. Findings that show a moderate age-related decline in the efficiency of switching (e.g., Cepeda, Kramer, & Gonzalez de Sather, 2001; Kra- mer, Hahn, & Gopher, 1999; Kray, Li, & Lindenberger, 2002; Kray & Lindenberger, 2000; Mayr, 2001) and others that show declining inhibitory efficiency (e.g., for reviews, see Hasher, Zacks, & May, 1999; McDowd & Shaw, 2000) jointly suggest that age-related deficits in task set switching, and by extension, sequential performance, are attributable to declines in similar inhibitory processes. Contrary to these findings, other researchers have shown age-equivalent inhibitory functioning in serial recall (Maylor & Henson, 2000) and task set switching (Mayr, 2001). Maylor, Schlaghecken, and Watson (2005) proposed that inhibitory processes involved in post-response output and serial behavior may be age-invariant. Given the small 0001-6918/$ - see front matter Crown Copyright Ó 2007 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.actpsy.2007.08.006 * Corresponding author. Tel.: +1 514 848 2424; fax: +1 514 848 2815. E-mail address: karen.li@concordia.ca (K.Z.H. Li). www.elsevier.com/locate/actpsy Available online at www.sciencedirect.com Acta Psychologica 127 (2008) 416–427