Reinforcement in applied behavior analysis (ABA) is the process of following a behavior with a consequence that makes that behavior more likely to happen again. It’s the core mechanism behind how ABA therapy builds new skills and encourages positive behaviors. When a child says “please” and immediately gets the item they asked for, that access to the item is reinforcement, and the child is more likely to say “please” next time.
The concept sounds simple, but ABA practitioners use a detailed framework of reinforcement types, timing strategies, and assessment methods to make it work consistently across different situations and individuals.
Positive vs. Negative Reinforcement
These two terms confuse almost everyone at first, because “negative” doesn’t mean “bad.” Both types of reinforcement increase a behavior. The difference is how.
Positive reinforcement means adding something desirable after a behavior. A child completes a task and receives praise, a sticker, or time with a favorite toy. The “positive” refers to adding a stimulus, not to a value judgment.
Negative reinforcement means removing something unpleasant after a behavior. A child puts on noise-canceling headphones to escape overwhelming sound, and the relief makes them more likely to use the headphones again. The “negative” refers to taking something away. Another example: a student finishes their worksheet and the teacher removes the requirement to do an extra assignment. The removal of that demand reinforces completing the worksheet.
In both cases, the outcome strengthens the behavior. The Behavior Analyst Certification Board’s ethics code requires that practitioners prioritize positive reinforcement procedures when designing interventions, turning to more restrictive approaches only after less intrusive methods haven’t produced results.
Primary and Secondary Reinforcers
Not all reinforcers work the same way, and understanding why matters for making reinforcement effective.
Primary reinforcers have innate value. They satisfy biological needs: food, water, sleep, touch, warmth. Nobody has to learn that these things are rewarding. A small snack after a correct response works as a reinforcer because hunger is built into human biology.
Secondary reinforcers (also called conditioned reinforcers) have no built-in value. They only become reinforcing because they’ve been paired with something that already is. Praise works because it’s linked to affection and social connection. Stickers on a behavior chart work because they’ve been connected to earning a prize. Token systems in ABA therapy rely entirely on this principle: tokens mean nothing on their own but become powerful motivators once a child learns they can be exchanged for preferred items or activities.
Money is the most familiar secondary reinforcer in everyday life. It’s just paper or numbers on a screen, but it buys things that satisfy real needs.
How Therapists Find the Right Reinforcer
A reinforcer only works if the individual actually finds it motivating, and what motivates one person may bore another. ABA therapists use structured preference assessments to figure out what will be most effective for each person.
Free operant observation is the most natural approach. The therapist watches the individual during play or unstructured time, recording which items or activities they gravitate toward, how long they engage with each one, and how often they return to it. This can happen in a clinic or at home.
Paired stimulus assessments present two items at a time and ask the individual to choose one. By rotating through many combinations, the therapist can rank preferences based on which items are chosen most consistently.
Multiple stimulus without replacement (MSWO) takes this further by presenting several items at once. After each choice, the selected item is removed from the array, forcing a new selection from the remaining options. This builds a clear hierarchy from most preferred to least preferred.
These assessments aren’t one-time events. Preferences shift over time, so therapists reassess regularly to make sure the reinforcers they’re using still carry weight.
Why the Same Reinforcer Doesn’t Always Work
A reinforcer’s power fluctuates depending on the individual’s current state. ABA uses the concept of motivating operations to explain this.
When someone has been deprived of something, its value goes up. A child who hasn’t had screen time all day will find tablet access highly reinforcing. This is called an establishing operation: the condition of wanting something makes the reinforcer more potent.
The opposite is satiation. If a child has been snacking all morning, offering a cracker after a correct response won’t motivate much. This is an abolishing operation: having had enough of something reduces its reinforcing power. Effective ABA practice accounts for these shifts by rotating reinforcers, limiting free access to highly preferred items before therapy sessions, and reading the individual’s current motivation in the moment.
Schedules of Reinforcement
How often reinforcement is delivered matters as much as what the reinforcer is. ABA uses four main schedules, each producing different patterns of behavior.
- Fixed ratio: Reinforcement comes after a set number of responses (every 5 correct answers, for example). This produces a high rate of responding with a brief pause right after each reinforcement. Think of a factory worker paid per item produced: they work fast, take a short break after getting paid, then resume.
- Variable ratio: Reinforcement comes after an unpredictable number of responses. This generates the highest and steadiest response rates with almost no pausing. Slot machines operate on this schedule, which is why they’re so compelling.
- Fixed interval: Reinforcement becomes available after a set amount of time. People tend to respond slowly right after reinforcement and speed up as the next opportunity approaches. Studying for an exam that’s always on Friday follows this pattern: most studying happens Thursday night.
- Variable interval: Reinforcement becomes available after unpredictable time periods. This produces a moderate, steady rate of responding. Checking your phone for messages is a real-world example, since messages arrive at irregular times.
In practice, ABA therapists often start with continuous reinforcement (reinforcing every single correct response) when teaching a new skill. Once the skill is established, they gradually shift to intermittent schedules, which make the behavior more durable and resistant to fading over time.
Differential Reinforcement
When the goal is reducing a problem behavior rather than just building a new one, ABA uses differential reinforcement. The basic idea: reinforce what you want to see more of while withholding reinforcement for what you want to see less of. There are three common forms.
Differential reinforcement of alternative behavior (DRA) reinforces a different, acceptable behavior that serves the same purpose as the problem behavior. If a child acts out to get attention, the therapist reinforces raising a hand or asking politely instead. The key is that the replacement behavior has to meet the same need.
Differential reinforcement of incompatible behavior (DRI) is more specific. It reinforces a behavior that physically cannot happen at the same time as the problem behavior. A child who throws objects can be reinforced for keeping both hands on the table during an activity, since they can’t throw something while their hands are flat on the surface.
Differential reinforcement of other behavior (DRO) reinforces the absence of the problem behavior over a set time period. If a child doesn’t engage in the target behavior for, say, five minutes, they receive reinforcement. The intervals can be gradually lengthened as the behavior decreases.
Natural vs. Contrived Reinforcement
One of the biggest challenges in ABA is making sure skills learned in therapy actually show up in everyday life. A child may answer questions perfectly during structured drills but go silent when a teacher asks the same question in class. This gap often comes down to the type of reinforcement being used.
Contrived reinforcers, like tokens or candy after a flashcard drill, don’t exist in the real world. Natural reinforcers do. When a child says “bubbles” and gets to play with bubbles, the reinforcer is directly tied to the behavior. When a child says “juice” at dinner and someone pours juice, that’s natural reinforcement in action.
Naturalistic teaching strategies in ABA lean heavily on this principle. Instead of sitting for repetitive drills, children practice skills during real routines. At home, mealtime becomes a chance to practice requesting (“Say ‘juice’ before I pour”). At school, recess supports turn-taking on swings. Bedtime routines teach sequencing (“first toothpaste, then brush”). The reinforcement is built into the activity itself, which makes the skill far more likely to transfer across settings and people.
The most effective ABA programs typically blend structured and naturalistic approaches, starting with contrived reinforcement to establish a skill and then transitioning to natural reinforcers so the behavior sustains itself in daily life.