Subadditivity effect

Biological Parallel

Ground squirrels increase total vigilance time when threats partition (hawk + fox + snake = 45% of time) versus single aggregate threat (predators = 30% of time). Decomposing danger into specific categories activates independent fear modules, amplifying total response beyond the general threat. This produces subadditivity: sum of specific probabilities exceeds general category probability. Investors estimate higher total bankruptcy risk when prompted for 'recession scenario + debt crisis + disruption' than 'all bankruptcy causes,' project managers summing task-specific delays predict longer timelines than aggregate estimates, physicians summing disease-specific mortality risks exceed all-cause mortality. Partitioning exploits modular psychology.