There may be nothing special about the association between working memory capacity and fluid intelligence

• WMC and gf share 60% of their true score variance in children.
• gf is a stronger indicator of g than WMC in children.
• The gf and WMC association is mediated completely by g.

The association between working memory capacity (WMC) and fluid intelligence (gf) has been described as substantial and important. In a recent investigation, Gignac (2014a) contended that WMC and gf share closer to 60% of their variance, rather than the commonly cited 50%, based on an analysis of the Wechsler Adult Intelligence Scale—IV (Wechsler, 2008) normative sample (N = 2200). However, Gignac's (2014a) investigation was limited in that it included only completely homogeneous gf (spatial) and WMC (verbal) subtests, as well as only adults in the sample. Consequently, the purpose of this investigation was to replicate and extend Gignac (2014a) by estimating the association between WMC and gf, based on the Wechsler Intelligence Scale for Children—Fifth Edition (Wechsler, 2014) normative sample (N = 2200), which includes a mix of verbal and spatial WMC subtests. Based on a correlated two-factor model, the correlation between WMC and gf was estimated at .77 (r2 = .59) which is a perfect replication of Gignac (2014a). However, based on a higher-order model which included all 18 of the WISC-V's subtests, the association between WMC and gf was found to be non-significant (− .10, p = .152) after controlling for the effects of general intelligence. Consequently, the commonly suggested notion that WMC and gf share unique cognitive and or neural processes was not considered supported, based on the results of this investigation.