Lesson 3: ABA Core Principles

Applied Behavior Analysis (ABA) is based on a number of fundamental principles that guide behavior modification. This lesson provides a detailed overview of the key concepts and techniques used in ABA.

Three-term contingency (ABC)Behavior typically occurs in a predictable sequence.  A preceding stimulus, known as the antecedent, provokes or triggers a behavior. After the behavior occurs, a consequence follows as another stimulus change in the environment. In applied behavior analysis, the antecedent-behavior-consequence sequence is called the three-term contingency (ABC). The three-term contingency (ABC) represents the central concept of behavior analysis. It is the fundamental unit of operant, or learned behavior, in behavior analysis based on the causal relationship between the antecedent, the behavior, and the consequence within the environment.

Antecedents and consequences

Environmental stimuli that influence behavior fall into two categories:

1. Antecedents: The first category of stimuli that occur before the behavior occurs is antecedents, which include discriminative stimuli and motivational conditions that occur or are in place before the behavioral response occurs. Knowing which stimuli trigger a behavior allows you to add or remove them from the environment, increasing or decreasing cues for a particular behavior.

1. Consequences: The second category of stimuli are consequences, which occur after the behavior. Consequences are also changes in the environment.   However, they occur immediately after our behavior and affect the frequency of this behavior in the future. Behavior is influenced through consequences by being strengthened (reinforcement) or weakened (punishment). If we know which consequences strengthen the behavior and which consequences weaken the behavior, we can modify those consequences to increase acceptable behavior and decrease challenging behavior.

Reinforcement

Reinforcement is a process that increases the likelihood that a behavior will occur again in the future. It involves providing a consequence (something that happens after a behavior) that strengthens that behavior.

In simple terms, reinforcement is anything that makes a behavior more likely to be repeated. For example:

• A child receives praise after sharing a toy, making them more likely to share again
• An employee receives a bonus after exceeding sales targets, encouraging them to continue performing well

Reinforcement can be either positive (adding something desirable) or negative (removing something unpleasant). Despite its name, negative reinforcement is not punishment, both positive and negative reinforcement strengthen behaviors, just through different processes.

• Reinforcement is a process that takes place over time.  Since it is a process, it has not taken place after only one instance. It needs to continue occurring to change a behavior, and seeing the change in the future frequency of the behavior determines whether reinforcement actually took place or not. Reinforcers need to be provided as immediate consequences of behavior for reinforcement to be used effectively. There are main categories of reinforcers (the preferred stimuli used in the process of reinforcement). These include unconditioned reinforcers (e.g., food, sleep, water, movement, touch), conditioned reinforcers (e.g., approval, attention, activities, toys), and generalized conditioned reinforcers (e.g., grades, rewards, money, tokens). Additionally, reinforcers can be assigned to categories such as: edible reinforcers, sensory reinforcers, tangible reinforcers, activity reinforcers, and social reinforcers.

• Reinforcement: affects several dimensions of behavior, each of which can influence how a behavior manifests. These dimensions include:
• Frequency: Refers to the number of times a behavior occurs in a given period of time. For example, if a student receives reinforcement every time, they complete an assignment, the frequency of completing assignments may increase.
• Duration: It is the total time that is dedicated to performing a behavior. For example, if a student receives reinforcement for reading, the length of reading sessions may increase.
• Latency: It is the time that elapses between the presentation of a stimulus (e.g., being asked a question) and the individual’s response. For example, if a student receives reinforcement for responding quickly to a question, the latency of their answers may decrease; meaning they may answer the questions quicker in the future.
• Intensity: Refers to the strength or magnitude of the behavior. For example, if a student receives reinforcement for speaking loudly during a presentation, the intensity of their voice may increase.
• Form (topography): It is the physical configuration of behavior, that is, how it is performed or what it looks like. For example, if a student receives reinforcement for writing legibly, the form of his or her writing may improve.

Functions of Behavior

Understanding reinforcement and the function of behavior creates a powerful framework for behavior change. Reinforcement—the process that increases behavior—works most effectively when aligned with why a behavior occurs in the first place. For example, if a child’s disruptive classroom behavior serves an attention-seeking function, providing attention (even negative attention) reinforces that behavior, making it more likely to continue. By identifying that the function is attention, more appropriate behaviors can be reinforced instead—perhaps teaching the child to raise their hand to speak and heavily reinforcing this alternative. Similarly, if a behavior functions as escape from demands, reinforcing task completion with breaks can reshape behavior patterns. The key insight is that reinforcement strategies should be tailored to address the specific function driving a behavior, rather than applying a one-size-fits-all approach. This function-based perspective allows teachers to both decrease problem behaviors and increase appropriate alternatives by systematically adjusting how reinforcement is applied.

In behavioral analysis, there are four main functions that explain why people behave the way they do:

1. Attention – Behaviors to get social attention or reactions from others

1. • Example: A child calls out in class to get the teacher to notice them

1. • Example: An adult posts on social media to receive likes and comments

1. Escape/Avoidance – Behaviors to get away from or avoid something unpleasant

1. • Example: A student acts out to get sent out of a difficult class

1. • Example: Calling in sick to avoid a stressful meeting

1. Access to Tangibles – Behaviors to obtain desired items or activities

1. • Example: A child throws a tantrum to get a toy at the store

1. • Example: Working overtime to earn money for a vacation

1. Sensory Stimulation – Behaviors that provide sensory feedback or internal pleasure

1. • Example: Hand-flapping that provides visual stimulation

1. • Example: Humming that creates pleasing auditory input

Understanding these functions helps identify why someone engages in a particular behavior, which is crucial for developing effective interventions. Rather than just focusing on stopping a behavior, identifying its function allows for teaching more appropriate behaviors that serve the same purpose.

Modeling and Shaping

Understanding how to use reinforcement is also key in applying ABA-based intervention techniques effectively.  Modeling and shaping are two powerful reinforcement-based teaching strategies used in Applied Behavior Analysis (ABA). Modeling involves demonstrating the desired behavior so the learner can observe and imitate it, essentially learning through observation. For example, a teacher might model appropriate social greetings for a child to copy. Shaping, meanwhile, reinforces successive approximations toward a target behavior that might be too complex to learn all at once. Rather than waiting for perfect performance, teachers reward small steps in the right direction, gradually raising expectations until the complete behavior is achieved. These techniques are often used together in ABA interventions—a teacher might first model a skill like skipping, then use shaping to reinforce the learner’s increasingly accurate attempts at engaging in a behavior that looks like the desired action of skipping independently.

Extinction

Extinction in Applied Behavior Analysis (ABA) is the process of stopping or weakening an unwanted behavior by no longer providing the reinforcement that was previously maintaining it.Thus, the behavior stops being reinforced and its frequency gradually decreases. The effectiveness of an extinction procedure depends on an accurate identification of the function of the behavior and the consequences that contribute to its occurrence. There are three methods of using extinction, depending on the type of reinforcement maintaining the behavior:

Extinction for behavior that is supported by positive reinforcement: In cases where the behavior is maintained by positive reinforcement, elimination of positive reinforcement is used. So, if in the past the behavior of calling out was maintained by getting a response from the teacher, the teacher would use extinction by no longer responding to the calling out.

Extinction by behavior that is supported by negative reinforcement: If the behavior is maintained by negative reinforcement, extinction involves preventing the behavior from achieving the elimination of the aversive (unpleasant) stimulus. This means that the behavior no longer results in avoidance or escape from the aversive condition, leading to a decrease in that behavior over time. For example, this might mean no longer allowing the child to get out of doing an assignment when he rips up the worksheet because you have another one ready.

Extinction for behavior that relies on automatic reinforcement: In this case, sensory extinction is used. It is carried out by weakening or eliminating sensory consequences. In this case, you would try to stop the behavior from meeting the sensory consequence, for example, unplugging a lamp so that the reinforcement from turning the switch on and off repeatedly no longer occurs.”

The result of the extinction procedure is the gradual reduction of the behavior. However, an initial temporary increase in undesirable behavior, known as an “extinction burst,” can occur. During this phase, the behavior may intensify before it begins to subside. The effectiveness of the extinction procedure depends on identifying all possible sources of reinforcement for the undesirable behavior and ensuring that these reinforcers are not available. When using the extinction method, the professional must reinforce the socially acceptable alternative behavior, which should serve the same function or purpose as the unwanted behavior that you are working to decrease.