Habits are patterns of behavior that we automatically repeat in familiar situations. They emerge through consistent repetition and the learning of associations between stimuli and responses.
Think of simple actions like making a cup of coffee in the morning or taking the same route to work: these tasks, once learned, do not require much mental effort. The key here is cognitive efficiency.
When we transform deliberate behaviors into automatic ones, we free up mental resources for more demanding tasks. For example, when you move to a new city, every turn or intersection on the way to work initially requires your full attention.
However, over time and with repetition, these actions become automatic. This not only makes everyday life easier but also allows you to use your attention for more complex problems, such as planning your day or thinking through important decisions.
Habits are particularly useful when we are stressed, rushed or distracted, as they require less conscious effort.
They can ensure that you continue to do important things, such as exercising regularly or eating healthily, even when motivation is low. In this way, they serve as a kind of “autopilot” for desirable behaviors.
Despite their usefulness, habits can become a barrier when the context changes. Imagine traveling to a country where you drive on the opposite side of the road. There is a high chance that you will make mistakes initially because your habit is so ingrained.
Similarly, changing an old password can be challenging because muscle memory and automatic behavior insist on the previous pattern.
These challenges, known as action slips, are small mistakes caused by the conflict between old habits and new demands.
In addition, habits can also contribute to harmful behaviors, such as compulsions in obsessive-compulsive disorders (OCD) or addictions, where repetitive actions become difficult to control.
The study of habits has attracted both researchers interested in the theory and practitioners seeking to apply these discoveries in the real world. Basic science on habits focuses on understanding how automatic behaviors form and how we can influence them.
Applied research, on the other hand, seeks ways to encourage “good habits” and curb “bad” ones, promoting meaningful behavioral changes. Habits can be understood as the result of two distinct mental systems:
Stimulus-response (S–R) associations: Here, habits form when a stimulus (such as a cell phone alarm) automatically triggers a response (checking the phone). This process is rapid and automatic.
Goal-directed control: In some situations, even automatic behaviors can be modulated by our conscious attention and goals, as long as cognitive resources are available.
The two systems are always interacting. Habits occur when the stimulus-driven system overrides the goal-driven system at that moment, such as when you unwittingly take your usual route home, even though you planned to stop somewhere else.
However, habits do not always rely exclusively on the S–R system. Some research suggests that other mechanisms are involved, especially in situations where the context changes or there is a conflict between old habits and new goals.
While the science of habits has advanced significantly, there are still areas where the data are inconsistent. For example, while there is consensus on how simple habits form, questions such as their application in clinical settings (OCD or addictions) or strategies for lasting change are still being explored.
This area of study has the potential to influence practical interventions, helping people build positive behaviors and overcome harmful patterns.
Understanding how the brain handles habits at the neurobiological and psychological levels continues to be one of the most promising frontiers in behavioral science.
(A) The path home is habitual, guided by stimulus-driven processes, where a specific stimulus (e.g., a tree at a junction) automatically triggers an associated response (e.g., turning left). In contrast, goal-driven actions involve the consideration of action-outcome (A–O) expectations (e.g., turning right to go to the store) and the evaluation of valued outcomes (e.g., getting food). (B) When both control systems align, the resulting behavior is the same, making it difficult to determine which system is driving the action. However, when the two systems conflict, habits become evident because they run counter to explicit beliefs and goals.
Habits can be strengthened by increasing the strength of the stimulus-driven system, which occurs through the repetition of an action in the same context. Or, by reducing the influence of the goal-driven system: Simple tasks, with less need for reasoning, help habits “take over.”
To avoid or break a habit, we can weaken the stimulus-oriented system by changing the environment or reducing the frequency of repetitions. We can also strengthen the goal-oriented system by maintaining focus on goals and increasing attention to unwanted behavior.
Habit formation is facilitated by factors that strengthen the stimulus-driven system or weaken the goal-driven system. Conversely, breaking habits can be achieved through factors that weaken the stimulus-driven system or strengthen the goal-driven system. Abbreviation: S–R, stimulus–response.
Repetition is essential for turning behaviors into habits. Each time we repeat an action, our brain strengthens the connections between stimulus and response, making the behavior increasingly automatic.
This happens because the neurons involved in these actions "learn" to fire together, creating a memory trace that facilitates the habit.
For example, classic experiments in rats show that when the animal is trained to press a lever in exchange for food, it continues to press it even after the food has lost value, indicating that the behavior has become an automatic habit.
In humans, however, the relationship between repetition and habit is more complex. Studies show that some simple habits can be formed in just a few days, such as an action repeated thousands of times in a laboratory.
More complicated habits, such as adopting an exercise routine, can take weeks or months, depending on factors such as motivation and consistency.
Research suggests that a stable environment is crucial. For example, a hospital environment, where tasks are repeated daily (such as washing hands), encourages habit formation more quickly.
Neuroscience also helps explain habits by identifying the brain regions involved. The dorsolateral striatum (in rodents) or posterior putamen (in humans) are areas of the brain that are linked to stimulus-response learning. Studies show that damage to these regions impairs habit formation.
The goal-directed pathway extends from the anterior putamen and caudate to the dorsolateral prefrontal cortex (dlPFC), which supports goal-directed control by representing response and outcome identities and comparing the values of different responses. The ventromedial prefrontal cortex (vmPFC) is involved in retrieving goal values and determining their relative preferences, while the orbitofrontal cortex (OFC) is sensitive to changes in outcome values. The stimulus-directed pathway extends from the posterior putamen to the premotor cortex, a connection that is associated with individual differences in habit expression during a devaluation test. The posterior putamen has also been implicated in habit formation and expression; it shows increased activity with overtraining and decoding of action-related activity at the time of stimulus presentation. It is also associated with real-life habits that function as skills, such as driving.
Despite significant advances, research still faces challenges in fully understanding habits in humans, due to the difficulty of controlling variables in real-world studies.
Although it is popularly said that it takes 21 days to form a habit, the truth is that the time required varies. Studies show that simple habits can be formed in weeks. On the contrary, more complex behaviors, such as regular exercise, can take months.
The median time to achieve considerable automation is about 66 days, but it can vary between 18 and 254 days, depending on factors such as frequency, context, and motivation.
Reinforcement is an essential mechanism in the formation of habits. According to the Law of Effect, behaviors followed by positive results tend to be repeated, as they strengthen stimulus-response (S–R) associations. For example:
Rewards increase the likelihood of recurrence: Reinforcement promotes automaticity, as evidenced by faster reaction times in habitual behaviors.
Reward value influences habits: Studies show that trained associations with more valuable rewards present greater S–R interference, demonstrating that reinforcement independent of repetition can consolidate habits.
Furthermore, reinforcement is largely mediated by the dopamine system, especially in the dorsolateral striatum, which regulates automatic behaviors.
Research suggests that damage to the dopamine system disrupts S–R learning. Furthermore, during habit formation, dopamine activity increases in stimulus-oriented regions and may decrease in goal-oriented areas.
This dependence on dopamine also has implications for medical conditions such as Parkinson’s disease and Tourette’s syndrome, where dopamine dysfunction affects habit expression.
Another way to promote habits is by reducing the role of the goal-oriented system, which allows S–R associations to dominate. This can occur in several ways. Acute stress can weaken the brain’s ability to process deliberate goals, favoring habits. In stressful situations, S–R representations become more robust.
Distractors such as increased working memory or multitasking also reduce goal-directed control, facilitating habit formation. Finally, lack of sleep decreases cognitive engagement, creating an environment where habits are more easily expressed.
In the brain, this process is related to the prefrontal cortex (PFC), which is responsible for goal-directed planning and control. Decreased activity in the PFC, such as under stress, weakens the ability to regulate habits.
Research on compulsive disorders such as OCD shows that deficits in goal-directed control are associated with increased expression of habits. Patients with OCD, for example, demonstrate a higher prevalence of habitual behaviors, even after limited training.
This suggests that these disorders may be caused in part by dysfunctions in the A–O system, rather than by overactivity of the S–R system.
These insights are critical for therapeutic interventions that aim to adjust the balance between stimulus- and goal-oriented processes, both in clinical settings and in the formation of healthy habits in everyday life.
Habit extinction requires strategies that create new associations (such as linking a context to nonresponse), rather than simply suppressing existing behaviors.
Methods such as behavioral therapy and pharmacological interventions, such as the use of D-cycloserine, have shown efficacy in facilitating the extinction of S–R associations.
Changing the environment or avoiding cues related to the habit is an effective technique. For example, a smoker can avoid places where smoking is associated with social interactions.
Major life transitions, such as moving house, provide opportunities to break habits, but they can also disrupt positive habits.
Strengthening cognitive control and the ability to resist automatic responses helps to replace old habits with adaptive behaviors. Introducing new habits to replace old ones, and focusing on actions that use similar contexts, allows one to overcome unwanted habits.
These strategies show that habit modification requires an understanding of the interactions between context, environmental cues, and the brain control systems involved.
The goal-directed inhibition approach seeks to suppress stimulus-response (S–R) associations by promoting conscious control over automatic habits. This technique is especially relevant in contexts where maladaptive habits persist due to the strength of pre-established associations.
Factors such as stress, time pressure, and working memory load weaken the capacity for conscious control. Avoiding these contexts helps limit the expression of negative habits.
One study showed that chronic stress increases the expression of habits while reducing activity in goal-directed brain pathways such as the medial prefrontal cortex and caudate nucleus. After 6 weeks without stress, maladaptive habits decreased.
Goal simulation (visualization of future goals) is a powerful tool with therapeutic benefits for addictive behaviors.
Motivational interventions, such as structured feedback and monetary incentives, also help inhibit habits. Contingency management, which rewards specific behaviors, is widely used in substance use disorders.
Techniques such as transcranial direct current stimulation of the dorsolateral prefrontal cortex (dlPFC) have been shown to improve proactive control. These interventions hold promise in the management of behavioral and addictive disorders.
Forming competing habits, or “habit replacement,” is a complementary strategy that involves creating alternative S–R associations.
The combination of goal-directed inhibition and habit replacement represents a breakthrough in the treatment of problematic habits. Therapies such as cognitive behavioral therapy and brain stimulation techniques already integrate these principles, providing robust interventions for a variety of disorders, such as anxiety, addictions, and compulsions.
Future approaches aim to further explore the interactions between stimulus-directed and goal-directed systems, improving our understanding of how human behavior is shaped.
(A) Habit expression is influenced by response preparation time. The stimulus-driven control system engages rapidly, making habit expression more pronounced at shorter response preparation times. In contrast, the goal-driven system requires more time to fully engage, effectively inhibiting habit expression at longer response preparation times. (B) The strength of the stimulus-driven system can vary (e.g., it increases with repetition), making habit expression more likely, especially at shorter response preparation times. (C) The strength of the goal-driven system can also vary (e.g., it can be lower under conditions of stress or in individuals with obsessive-compulsive disorder, OCD), leading to increased habit expression even at longer response preparation times.
READ MORE:
Leveraging cognitive neuroscience for making and breaking real-world habits
Eike K. Buabang, Kelly R. Donegan, Parnian Rafei, and Claire M. Gillan
Cell, November 04, 2024
DOI: 10.1016/j.tics.2024.10.006
Abstract:
Habits are the behavioral output of two brain systems. A stimulus–response (S–R) system that encourages us to efficiently repeat well-practiced actions in familiar settings, and a goal-directed system concerned with flexibility, prospection, and planning. Getting the balance between these systems right is crucial: an imbalance may leave people vulnerable to action slips, impulsive behaviors, and even compulsive behaviors. In this review we examine how recent advances in our understanding of these competing brain mechanisms can be harnessed to increase the control over both making and breaking habits. We discuss applications in everyday life, as well as validated and emergent interventions for clinical populations affected by the balance between these systems. As research in this area accelerates, we anticipate a rapid influx of new insights into intentional behavioral change and clinical interventions, including new opportunities for personalization of these interventions based on the neurobiology, environmental context, and personal preferences of an individual.
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