Rats in a maze
explain your phone habit.

Journalist Charles Duhigg popularized the term "habit loop" in his 2012 book The Power of Habit, describing habits as a three-part cycle: a cue triggers a routine, which delivers a reward that reinforces the loop. In later work, Duhigg added a fourth piece, craving, the anticipation of the reward that actually drives the routine forward: cue, craving, routine, reward.

The neuroscience behind the model comes largely from MIT researcher Ann Graybiel, who ran rats through a T-shaped maze for chocolate while recording their brain activity. Early in training, the prefrontal cortex, the brain's deliberate decision-making region, was highly active on every run. As the behavior became habitual, that activity shifted into the basal ganglia, a deeper structure that stores routines as automatic sequences, and the prefrontal cortex went quiet during the run itself, engaging only around the reward.

A cue is anything that triggers the sequence, boredom, a notification, a specific location, a certain time of day. The craving is the anticipation that follows, the felt pull toward the reward before you've done anything yet. The routine is the behavior itself, opening the app, and the reward is whatever reinforces the loop enough to make it happen again next time.

Duhigg's addition of craving matters because it's often the strongest part of the cycle, stronger than the reward itself. Once a cue reliably predicts a craving, the craving alone can drive the routine forward even on days the reward turns out to be underwhelming, a scroll that delivers nothing interesting still gets repeated tomorrow.

Graybiel's finding that habits migrate into the basal ganglia explains something people who've tried to "just decide" to stop a habit run into constantly: the decision-making part of the brain isn't fully in the loop anymore. Once a behavior is chunked into the basal ganglia, running it requires very little conscious input, which is exactly what makes habits efficient, and exactly what makes them hard to interrupt through willpower alone.

This is confirmed in both rats and humans, not just an animal-model curiosity. The pattern holds up as a genuine account of how repeated behavior becomes automatic in people, which is part of why habits, distinct from a fresh decision made every time, tend to survive good intentions.

App design teams are, in effect, engineering cues on purpose: a badge, a banner, a sound, each one built to trigger the craving stage reliably. The routine, opening the app, is made as frictionless as possible, one tap from any home screen. And the reward is often intermittent and unpredictable, a new post, a like, a message, which per basic reinforcement research makes the loop harder to extinguish than a reward that's always the same size.

None of this requires the app to be malicious in intent. It requires the app to be optimized for engagement, and a well-built habit loop is one of the most reliable ways to produce engagement, whether or not that's the outcome you'd choose for yourself.

Trying to eliminate every cue is close to impossible, boredom itself is a cue. A more reliable point of intervention is the routine step, the actual act of opening the app, since removing that removes the reward it would have delivered, which over time weakens the whole loop.

Fella blocks selected apps by default, so the routine simply isn't available when a cue or craving hits. One 5-minute emergency unlock a day covers a genuine need, and the block returns automatically when the window ends, no decision required in the moment the craving shows up.