Isolation effect

Biological Parallel

Novelty detection operates through contrast, not absolute assessment—the hippocampus fires strongest when stimuli differ from context. When greater sage-grouse females evaluate males at leks, research shows they select mates based on relative dance quality, not absolute traits: commonalities (all inflate air sacs, all fan tails) become cognitively invisible. A 2025 study confirmed females choose males who display more than those who fight, ignoring aggression entirely—differential superiority is the selection criterion. Hippocampal CA1 neurons show robust firing rate increases specifically during novel object encounters while familiar objects trigger minimal response, creating 2-3x signal differences. Evolution built comparison engines, not absolute evaluators: identifying the best mate or detecting threats requires isolating what distinguishes options from each other and from baseline. The isolation effect is neural machinery designed for relative assessment.