Dopamine neurons respond especially strongly to novelty and to unpredictable, variable rewards — a pattern established decades ago by B.F. Skinner's research on variable-ratio reinforcement schedules in animals, which found that unpredictable rewards produce more persistent, harder-to-extinguish behavior than predictable ones. This is the exact mechanism slot machines are engineered around, and it's directly exploited by modern app design (infinite scroll, unpredictable notification content, variable-ratio 'like' counts): a reward that arrives unpredictably produces a stronger and more sustained dopamine response than one that arrives on a fixed, predictable schedule, which is why checking a feed that sometimes has something interesting and sometimes doesn't is more compulsively checkable than one that's reliably boring or reliably great every time.
Understanding this mechanism is useful precisely because it reframes the compulsion: struggling to put down a phone isn't primarily a willpower failure — it's a predictable response to a stimulus deliberately engineered around a well-documented neural reward pattern, the same one Skinner mapped in pigeons decades before smartphones existed. The most effective countermeasures target the mechanism (removing the variable-reward trigger — notifications off, app removed from the home screen) rather than relying on resisting it in the moment.