Storage capacity explains fluid intelligence but executive control does not Adam Chuderski a, ⁎, Maciej Taraday a , Edward Nęcka a , Tomasz Smoleń b a Jagiellonian University, Krakow, Poland b Pedagogical University of Krakow, Poland article info abstract Article history: Received 15 August 2011 Received in revised form 23 February 2012 Accepted 23 February 2012 Available online xxxx We examined whether fluid intelligence (Gf) is better predicted by the storage capacity of ac- tive memory or by the effectiveness of executive control. In two psychometric studies, we measured storage capacity with three kinds of task which required the maintenance of a visual array, the monitoring of simple relations among perceptually available stimuli, or the quick update of information. Executive control was measured with tasks reflecting three executive functions, namely attention control, interference resolution, and response inhibition. Using structural equation modeling, we found that all storage tasks loaded on one latent variable, which predicted on average 70% of variance in Gf (Studies 1 and 2). On the contrary, neither interference resolution nor response inhibition was substantially related to Gf or to any other variable (Study 1). Although attention control predicted on average 25% of Gf variance (Studies 1 and 2), when storage capacity was statistically controlled for, attention control no longer significantly explained Gf. © 2012 Elsevier Inc. All rights reserved. Keywords: Fluid intelligence Working memory Storage capacity Executive control 1. Introduction The last twenty years of research on individual differences in cognition have unquestionably enriched our understand- ing of fluid intelligence (Gf; also called fluid ability, fluid rea- soning, or reasoning ability), one of the most important human abilities, which is closely related to general ability (g factor). Gf indicates how well (or how poorly) people reason and solve problems in novel, abstract tasks. The main obser- vation shows that the capacity of working memory (WM), a cognitive mechanism responsible for active maintenance of information crucial for current processing, is the strongest predictor of Gf. Several studies (e.g., Ackerman, Beier, & Boyle, 2002, 2005; Colom, Abad, Rebollo, & Shih, 2005; Conway, Cowan, Bunting, Therriault, & Minkoff, 2003; Engle, Tuholski, Laughlin, & Conway, 1999; Kane et al., 2004; Süß, Oberauer, Wittmann, Wilhelm, & Schulze, 2002) estimated that working memory capacity (WMC), a latent variable being measured with either so-called complex span tasks or batteries of diverse WM tasks, shares a huge amount of common variance with Gf. According to different sources, this amount can be 50% (Kane, Hambrick, & Conway, 2005), 72% (Oberauer, Schultze, Wilhelm, & Süß, 2005), and even 92% (Colom, Rebollo, Palacios, Juan-Espinosa, & Kyllonen, 2004). However, what WM tasks really measure and why WM and Gf are so strongly related is very much disputed (e.g., Colom et al., 2005; Cowan, 2001; Engle & Kane, 2004; Kane, Conway, Hambrick, & Engle, 2007; Oberauer, Süß, Wilhelm, & Sander, 2007; Unsworth & Spillers, 2010). Several theories proposed different cognitive mechanisms presumed to underlie common variation in working memory and Gf. In the present paper, we focus on two influential groups of theories of such mechanisms. One group of theories suggest that individual performance in both WM tasks and Gf tests depends on the quality of control over some cognitive pro- cesses like directing attention or triggering responses (ability henceforth referred to as executive control). On the contrary, the other group of theories propose that the capacity (hence- forth called storage capacity) to simultaneously maintain the maximum possible amount of information in some kind of active memory is crucial for both WM and Gf. The general aim of our research was to confront the predictions of both approaches by estimating in one structural equations model (SEM) the coefficients of paths leading from latent variables Intelligence 40 (2012) 278–295 ⁎ Corresponding author at: Institute of Philosophy, Jagiellonian University, Grodzka 52, 31-044 Krakow, Poland. E-mail address: adam.chuderski@gmail.com (A. Chuderski). 0160-2896/$ – see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.intell.2012.02.010 Contents lists available at SciVerse ScienceDirect Intelligence journal homepage: