Gf(t) & Gf0 — Fluid Intelligence
Raw biological compute power: working memory capacity, abstract pattern speed, and novel reasoning. Peaks around age 22–24 (Gf0) and declines monotonically due to prefrontal senescence.
Gc(t) — Crystallized Intelligence
Accumulated mental models, domain abstractions, vocabulary, and compressed problem-solving heuristics. Built by investing Gf over time; can compound into your 60s.
h² ≈ 0.75 — Narrow-Sense Heritability
Proportion of population variance in adult general intelligence (g) attributable to additive genetic variance in twin and polygenic studies.
δ (Delta) — Prefrontal Senescence Slope
Speed of biological brain aging after age 24 (white-matter demyelination & synaptic pruning). Accelerated by vascular disease; slowed by aerobic Zone-2/VO₂ max fitness.
E & M — Epistemic Rigor & Practice
In Cattell's integral ∫ Gf·E·M dt, E is the structural depth of what you study (math/logic vs. trivia), and M is deliberate practice strain.
μ (Mu) — Entropy / Dogma Ossification
Rate at which your acquired Gc becomes obsolete or rigidified by ideological dogma. High if you memorize fleeting tool syntax; low if you master first principles.
Cowan's K — Working Memory Slots
Nelson Cowan's constant (~4 ± 1 chunks in an average adult). You cannot add more hardware slots, but high Gc packs exponentially more meaning into each slot.
dGf/dt & dGc/dt — Yearly Velocity
Instantaneous rate of change (in IQ points per year) at the inspected age. Notice the yellow circle on the chart where Gc crosses above Gf.