The Mortal Mind: Memory, Imagination, and Selection in a Colony of Simple, Fallible Agents

A companion study to The Currency of Thought (2026) reports the second round of a four-month experimental program (June-September 2026) that rebuilt a colony of simple cognitive agents around two structural lessons: an immortal safety skeleton makes cognition unnecessary, and choosable memory makes cognition defundable. The rebuild - Ant V2 - commits to a mortal (fallible) skeleton, continuous memory consulted every step, a food-first economy, an active Queen, and heritable cognition. Across ten reported campaigns with kill criteria, anti-vacuity probes, and a 24-test certifying suite, we show: (1) memory pays decisively when the world outdates the map (Cohen's d=+0.74) and is the colony's survival-bearing cognitive layer; (2) imagination completes a four-design arc - inert as memory-splice recombination, economically null when fully wired, anti-adaptive as evaluated plan-replay (d=-9.2), and vindicated as advice: the same evaluated plans delivered as 35% votes pay decisively (d=+0.75, 12/12 survival) - the dose-form law 'advice helps, possession kills', confirmed across mechanisms; (3) selection measurably enriches cognition (drift +0.31 to +0.45 as pressure rises, unanimous in the niche) but weakly and ubiquitously, not sharply by niche; and (4) a geometrically flat memory core suppressed recall to 0.085% of steps and masqueraded as cognitive nulls until diagnosed. What a cognitive act is - choosable or continuous, advice or possession, graded or flat - determines whether a colony of rational agents thinks, survives, and evolves.