Unit Bias
Unit Bias is a cognitive heuristic where individuals tend to consume or complete a "single unit" of a given item, regardless of its size or their actual need. Formalized by Geier, Rozin, and Doros in 2006, this mental model explains why we finish an entire bag of chips, why we feel compelled to reach "Inbox Zero," and how restaurant portion sizes directly drive overconsumption. By understanding the "Completion Reflex," decision-makers can design better products, health interventions, and productivity systems that leverage our natural desire for closure to drive positive habits.