Kyoto University researchers found one prefrontal pathway governs the switch to habit while another sets how intensely the habit is carried out, explaining individual differences.

Brushing your teeth, checking your phone, taking the same route to work: much of daily life runs on habit. Habits free the mind from having to deliberate over every routine action. They are also notoriously hard to break, which is why people struggle to drop bad ones and to establish good ones.

By some estimates, a large share of everyday behavior is habitual. One frequently cited study of college students’ diaries, by psychologist Wendy Wood and colleagues, found that around 40 percent of daily actions were performed almost every day and usually in the same context, a hallmark of habit.

“Habits are one of the brain’s most mysterious functions,” said Nozomi Asaoka, a co-corresponding author of a new study from Kyoto University. “We often struggle to control them even though they are our own actions. By uncovering how habits work, we may eventually find ways to take control of them rather than letting them control us.”

Working in mice, Asaoka and colleagues identified two distinct brain circuits involved in habits. One governs whether a behavior becomes a habit at all. The other controls how strongly that habit is carried out. The work is published in Nature Communications.

From goal to routine

Neuroscientists distinguish between two ways of choosing actions. Goal-directed behavior is deliberate: an animal or person acts because it expects a particular outcome and adjusts when that outcome changes. Habitual behavior is automatic: the action is triggered by a familiar situation and continues even when the reward no longer matters. In classic experiments, an animal trained to press a lever for food will, once the behavior becomes habitual, keep pressing even after it has eaten its fill.

Repetition is known to be necessary for that transition. But it has been unclear whether a habit is simply a carbon copy of the original behavior or whether the behavior itself changes as it becomes automatic.

Studying the question has been difficult because habits take a long time to form. In people, a well-known study from University College London found that forming a simple daily habit took anywhere from 18 to 254 days, with a median of about 66. Tracking the same animals’ behavior and brain activity across such a long transition is a challenge.

A fast track to habit

The Kyoto team developed a training method that produces habits rapidly in mice. The animals were first trained to use goal-directed strategies, then given four additional days of training designed to encourage habitual behavior. That two-stage design allowed the researchers to observe the shift from goal-directed to habitual behavior within the same individual animals.

The work focused on the prefrontal cortex, the region at the front of the brain involved in planning, decision-making and flexible behavior.

Two circuits, two jobs

The researchers found that a circuit running from the anterior cingulate cortex to the retrosplenial cortex determines whether a behavior becomes a habit. The connections in this pathway weaken during the transition from goal-directed to habitual behavior.

A second circuit, running from the lateral orbitofrontal cortex to the central striatum, controls how much the habit is performed once it has formed. That pathway accounted for differences between individual animals. Mice with strong neural responses in this circuit kept performing the habitual behavior at high levels, while those with weaker responses performed it less.

When the researchers artificially manipulated the two pathways, they could selectively promote habit formation or change how intensely the habit was carried out. The team describes this as showing that the two circuits play distinct roles.

The striatum, a structure deep in the brain, has long been linked to habits, and the orbitofrontal cortex is known to be involved in evaluating rewards. The new work adds detail by separating the decision to switch to habit from the vigor with which a habit is expressed.

Previous research in rodents has pointed to a division of labor within the striatum itself, with one subregion more involved in goal-directed actions and another in habits. How the prefrontal cortex feeds into that system, and whether different prefrontal pathways handle different aspects of habitual behavior, has been less clear. The Kyoto findings suggest it does, with separate inputs for forming a habit and for setting its strength.

Why habits differ

The key finding is that habit formation is more complex than the traditional view that repetition simply stamps an action into a routine. Even after a habit has formed, how often and how much the behavior is performed varies significantly between individuals.

“Our study has uncovered previously overlooked control mechanisms involved in habit formation, showing what determines how strongly a habit is carried out, helping explain why habits differ from person to person,” said team leader Yasunori Hayashi.

That distinction could matter for understanding why some people find it easy to maintain a routine while others struggle, and why some habits become overwhelming. Compulsive behaviors, such as those seen in obsessive-compulsive disorder, have been linked to an imbalance between goal-directed and habitual control.

From mice to people

The team plans to investigate what drives individual differences in habit strength, with the aim of helping people acquire beneficial habits and improving treatment for problematic ones, including those associated with obsessive-compulsive disorder.

There are reasons for caution. The study was conducted in mice, and the release does not report how many animals were used or give statistical details. Mouse habits formed over a few days of laboratory training are far simpler than the tangled routines of human life, and the brain regions involved, while broadly conserved, are not identical across species.

Still, the work offers a new way to think about habits: not as a single switch that flips from deliberate to automatic, but as two separate dials, one for whether a behavior becomes routine and another for how forcefully it runs.

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Notes

1. “Dissociable roles of prefrontal plasticity in decision making strategy and execution of habitual behavior.” Nature Communications, 27 July 2026. DOI: 10.1038/s41467-026-75706-1.
2. Kyoto University. “Unraveling the mysteries of habit formation.” EurekAlert!, 27 July 2026. https://www.eurekalert.org/news-releases/1137090.

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