Carbon is to life as g is to _____: A review of the contributions to the special issue on specific abilities in intelligence

Just as carbon infuses all life forms, g infuses almost all aspects of cognitive performance. This Special Issue focuses on specific abilities, defined as distinct abilities (e.g., verbal, math, spatial) that differ conceptually and empirically from g, which refers to variance common to tests. The nine contributions examine different specific abilities (e.g., spatial, academic, executive), involve different samples (e.g., humans, animals, countries), and compare different groups (e.g., males and females; gifted and nongifted). The contributions are discussed in terms of their support for a “primacy of g hypothesis,” which assumes that the validity of tests is largely attributable to g, or a “more than g hypothesis,” which assumes that specific abilities contribute to the validity of tests beyond g. The article summarizes each contribution and discusses models and theories of g and specific abilities (e.g., Cattell-Horn-Carroll and Verbal-Perceptual-Image Rotation models; investment and differentiation theories), with a focus on future research on specific abilities. Taken together, the contributions show that specific abilities are a meaningful addition to g but that their validity depends on the particular abilities, models, and theories being examined.