Operational Definitions: Clearly Define the Behavior

Operational definitions are the backbone of effective ABA. Without a clear, objective definition of the behavior you’re measuring, nothing else—data collection, FBAs, BIPs, or progress monitoring—works the way it should. A strong definition eliminates guesswork, improves treatment integrity, and allows every member of the team to collect data the same way.

Whether you’re defining a behavior you want to reduce or a skill you want to increase, your definition must be observable, measurable, and free of assumptions. The clearer your definition, the more reliable your data—and the more confidently you can design interventions that actually work.

This guide walks you through how to write operational definitions that are precise, defensible, and practical in real-world environments. You’ll learn the difference between topographic and functional definitions, how to decide which one to use, and how to create definitions that hold up across settings, staff, and situations.

What Is an Operational Definition?

An operational definition is a precise, objective description of a behavior so clear that anyone—regardless of experience—could read it and reliably identify whether the behavior occurred. It removes interpretation, emotion, and subjectivity, leaving only observable, measurable actions.

A strong operational definition:

• Describes only what can be seen or heard
  (No thoughts, feelings, or assumptions.)

• Is specific enough for two observers to agree
  (High interobserver agreement.)

• Includes parameters such as frequency, duration, intensity, or distance

• Uses examples and non-examples to avoid ambiguity

• Stays neutral and non-judgmental

Operational definitions support:

• Functional Behavior Assessments (FBAs)

• Behavior Intervention Plans (BIPs)

• Skill acquisition programs

• Data collection systems

• Progress monitoring

• Collaboration across home, school, and clinic environments

If you can’t define the behavior clearly, you can’t measure it clearly—so everything starts here.

Topographic vs. Functional Definitions

Topographic Definitions: Describing What the Behavior Looks Like

A topographic definition focuses on the form of the behavior—what an observer sees or hears. This is the most common type of operational definition used in ABA, especially when you need precision or when the function of the behavior is unclear.

A strong topographic definition answers questions like:

• What exactly does the learner do?

• How much movement, force, or distance counts?

• What does not count as the behavior?

Example of a topographic definition:

Throwing: Any instance in which the learner moves an object not intended to be thrown through space more than one foot using any part of the body.

Examples include:

• Pushing materials off a table so they fall more than one foot.

• Tossing a marker across the room.

• Kicking a box so the contents scatter across the floor.

Non-examples include:

• Sliding a puzzle piece across a table.

• Dropping items while walking.

• Throwing a ball in the gym as part of play.

When to use a topographic definition

Use a topographic definition when:

• You don’t yet know the function of the behavior

• You’re targeting a single, clearly observable action

• The goal is reliability across multiple observers

• Other behaviors produce similar outcomes, making a functional definition too broad

Topography keeps the focus on what can be observed with absolute clarity.

Functional Definitions: Describing What the Behavior Achieves

A functional definition identifies the purpose or consequence of a behavior—the effect it has on the environment or others. Instead of describing what the behavior looks like, functional definitions describe what the behavior does.

Functional definitions group behaviors into a response class: different topographies that share the same maintaining variable.

Example of a functional definition:

Avoidance Behaviors: Any instance in which the learner escapes or avoids a demand by physically removing themselves from the situation for more than 20 seconds.

Examples include:

• Flopping to the floor and remaining there for over 20 seconds after being told to line up

• Walking away more than 5 feet when asked to begin a task

Non-examples include:

• Verbally protesting but completing the direction

• Leaving the area for less than 20 seconds

When to use a functional definition

Use a functional definition when:

• Multiple behaviors serve the same function

• You want a concise definition that captures an entire response class

• The function is well-established and reliably maintained

• Intervention is based on treating the underlying maintaining variable

Functional definitions are powerful when you want to treat the function, not the form.

Click HERE to access a PDF with some of these examples.

Choosing Between Topographic and Functional Definitions

Use a Topographic Definition When:

• You need a precise, observable description of what the behavior looks or sounds like.

• You’re early in the assessment process and don’t yet know the function.

• The exact form of the behavior matters for safety or data accuracy (e.g., hitting vs. tapping).

• You want multiple observers to collect data with high consistency.

• Different behaviors could produce similar effects, making a function-based definition too broad.

Use a Functional Definition When:

• Multiple behaviors serve the same purpose and treating them as one response class is clinically appropriate.

• You already have reliable information about the function (e.g., escape, attention, access).

• You want a concise definition that captures variations in form without needing a separate definition for each.

• Intervention decisions are driven by the maintaining variable, not the behavior’s form.

In Short:

• Choose topographic when you need clarity, precision, and observer agreement.

• Choose functional when the function drives intervention and several behaviors fall under the same response class.

How to Write an Effective Operational Definition (Step-by-Step)

Creating a strong operational definition is one of the most important skills in ABA. A well-written definition removes ambiguity, increases interobserver agreement, and ensures everyone collecting data or implementing interventions is on the same page. Here’s a clear, practical process you can apply to any behavior.

Step 1: Decide Whether You Need a Topographic or Functional Definition

Before you write anything, determine what matters most:

• If you need to describe exactly what the behavior looks like → choose a topographic definition.

• If the purpose of the behavior matters more than the form → choose a functional definition.

Ask yourself:
“Do I care most about what the behavior looks like, or what it accomplishes for the learner?”
Your answer guides the entire structure of the definition.

Step 2: Describe the Behavior in Clear, Observable, Measurable Terms

Your description should answer:

• What does the behavior look like?

• How long does it last, or how much force is needed?

• What counts as one occurrence?

• Where does it start and end (onset and offset)?

Avoid:

• Vague language (“acting out,” “being defiant”)

• Labels (“aggressive,” “noncompliant”)

• Assumptions (“trying to annoy others,” “on purpose”)

Use only what can be seen or heard, not inferred.

Example (strong):
“Throwing: Moving an object not meant to be thrown through space more than one foot using the hand, arm, or foot.”

Step 3: Add Examples to Clarify What Counts

Examples serve as anchors for your team, especially when multiple behaviors fall within one category.

Examples should:

• Match the full definition

• Include different contexts

• Reflect the learner’s real behavior

Example:

• Pushing items off a shelf so they fall to the ground

• Throwing a pencil across the room

Step 4: Add Non-Examples to Clarify What Does Not Count

Non-examples are just as important — they prevent accidental over-reporting and increase reliability among staff.

Non-examples should:

• Be behaviors that could be confused with the target

• Show clearly why they don’t meet the definition

• Narrow the scope appropriately

Example:

• Dropping puzzle pieces while rotating the board

• Kicking a soccer ball during structured play

Step 5: Review for Ambiguity (Ask Someone Else to Read It)

Hand the definition to a colleague and ask:

• “Would you instantly know whether the behavior occurred?”

• “Is any part confusing or open to interpretation?”

• “Is there anything you would measure differently?”

If they have questions, refine the definition.

Step 6: Check for Red Flags Before Finalizing

A good operational definition should avoid all of the following:

• Using the behavior itself in the definition (“refusing to comply is…”)

• Including intentions or emotions (“attempts to annoy,” “angry yelling”)

• Defining by impact alone if impact varies widely (“any contact that leaves a mark” may be too broad)

• Overly complicated or overly vague phrasing

You want a definition that’s precise but also easy to use correctly.

Step 7: Finalize and Train Your Team

Even the best definition fails if people don’t know how to apply it.

Provide:

• A printed version

• A brief review with examples

• Practice identifying behavior from short scenarios or videos

• Clarification on how to record it (duration, frequency, latency, etc.)

Training ensures the whole team is aligned and data quality stays high.

Examples of Strong Operational Definitions

This video provides one example of a strong operational definition, more examples are provided below.

Operational Definition: Aggression

Aggression:
Any instance in which the learner makes physical contact with another person using their body or an object with enough force to produce an audible sound and/or leave a visible mark.

Examples include:

• Hitting an adult’s arm with an open or closed hand hard enough to make a sound.

• Kicking a peer such that a red mark appears on the skin.

• Throwing an object (not designed to be thrown) that strikes another person with sufficient force to produce a sound or mark.

• Biting another person, resulting in visible teeth marks or redness.

Non-examples include:

• Light taps that produce no sound or mark.

• Accidental contact while walking past someone.

• Falling onto a peer during play.

Operational Definition: Self-Injurious Behavior (SIB)

Self-Injurious Behavior (SIB):
Any instance in which the learner causes physical harm to their own body through hitting, biting, pinching, or head banging with enough force to produce a visible mark or audible sound.

Examples include:

• Banging the head against a wall, floor, or object.

• Biting the hand, arm, or wrist leaving teeth marks.

• Pinching the skin between fingers hard enough to cause redness.

• Hitting the face or head with the hand.

Non-examples include:

• Light tapping of the head during play.

• Accidental contact with the floor while sitting or flopping.

Operational Definition: Refusal / Non-Compliance

(Optimized to target the observable response rather than a mental state.)

Refusal:
Any instance in which the learner does not begin the requested action within 30 seconds of a clear directive, unless engaged in a competing behavior that is contextually appropriate.

Examples include:

• Failing to move toward the table within 30 seconds of being asked.

• Pushing materials away when instructed to begin work.

• Lying on the floor instead of transitioning.

Non-examples include:

• Beginning the task within 30 seconds.

• Delayed responding due to a reasonable barrier (tying shoes, toileting, carrying materials).

Alternative (preferred) target for skill-building:
Compliance: Beginning the requested task or action within 30 seconds of an adult directive.

Operational Definition: Flopping

Flopping:
Any instance in which the learner’s body suddenly becomes limp, resulting in the learner dropping to a kneeling, seated, or fully lying position on the floor.

Examples include:

• Falling to the knees while walking.

• Lying flat on the floor after receiving a directive.

Non-examples include:

• Sitting or lying down during a scheduled activity.

• Kneeling during circle time.

Operational Definition: Eloping

Eloping:
Any instance in which the learner moves more than 5 feet away from the supervising adult or designated area without permission.

Examples include:

• Walking across the classroom when asked to come to the table.

• Running down the hallway after being instructed to stay in the room.

Non-examples include:

• Moving around the room during free play when wandering is permitted.

• Walking to the shelf to select a toy during choice time.

Operational Definition: Tantrum

Tantrum:
Any instance in which the learner engages in two or more of the following behaviors at the same time for at least 3 seconds: crying, screaming, throwing objects, hitting, kicking, banging, or flopping.

Examples include:

• Screaming and flopping when denied access to a preferred item.

• Crying loudly while throwing materials after a demand is placed.

Non-examples include:

• Crying briefly due to injury.

• Throwing a ball during a structured activity.

Operational Definition: Crying/Screaming

Crying/Screaming:
Any vocalization louder than typical speaking volume lasting more than 3 seconds, with or without tears, in a context where crying is not expected or injury is not present.

Examples include:

• Loud crying with tears when asked to transition.

• Screaming without tears when denied access to a preferred item.

Non-examples include:

• Laughing, playful squealing, or giggling.

• Crying due to an injury.

Onset: First instance of loud vocalization.
Offset: 30 seconds of quiet.

Operational Definition: Swearing

Swearing:
Any instance in which the learner uses language considered inappropriate for the environment, including specific prohibited words identified by the team.

Examples include:

• Saying “sh—” or “f—” in the clinic or public settings.

• Using explicit language in response to a demand or frustration.

Non-examples include:

• Using socially acceptable alternatives (“shoot,” “fudge”).

• Using dispreferred but non-prohibited words.

Operational Definition: Throwing

Throwing:
Any instance in which the learner uses any part of the body to move an object not intended to be thrown through space more than one foot.

Examples include:

• Pushing materials off a table so they fall to the ground.

• Throwing a marker across the room.

• Kicking an object off a shelf.

Non-examples include:

• Sliding a puzzle board across a table.

• Throwing a ball during gross motor play.

Operational Definition: Climbing

Climbing:
Any instance in which the learner is indoors, not sitting or lying down, and has both hands and both feet off the ground on a surface more than 3 feet high.

Examples include:

• Standing on a kitchen counter.

• Climbing a bookshelf.

• Standing on the back of a couch.

Non-examples include:

• Standing on a step stool during a cooking activity.

• Sitting on a couch.

Operational Definition: Grabbing

Grabbing:
Any instance in which the learner curls their fingers around or into another person’s clothing, body part, or hair, without permission, except to prevent a fall or injury.

Examples include:

• Grabbing a peer’s shirt while walking past.

• Clutching a teacher’s hair.

• Grabbing a peer’s arm during play without permission.

Non-examples include:

• Grabbing someone to keep from falling.

• Gently touching a peer’s arm.

The Three Key Components of an Effective Operational Definition

Operational definitions only work when they produce consistent, objective, repeatable measurement. That means every person collecting data should be able to look at the learner, look at the definition, and record the behavior the exact same way. To accomplish this, every strong operational definition includes three essential components:

1. A Clear, Observable Description

Your definition must describe only what a person can see or hear, not what the learner might be thinking, feeling, intending, or trying to communicate.

A strong description answers questions like:

• What does the behavior physically look like?

• How do I know the moment it starts and stops?

• Is the definition free of subjective words (e.g., “angry,” “rude,” “defiant”)?

Weak example:
“Emma gets upset and hits.”

Strong example:
“Emma makes physical contact with another person using an open or closed hand with enough force to produce an audible sound.”

Notice the difference: one is guesswork, one is measurable.

2. Examples That Demonstrate the Behavior

Examples show data collectors exactly what counts as the behavior. They clarify the range of forms the behavior may take and reduce ambiguity.

Effective examples:

• Reflect the learner’s real behavior

• Cover a range of typical contexts

• Include different topographies if relevant

Example (Throwing):

Examples include:

• Throwing a marker across the room.

• Pushing materials off a table so they land on the floor.

• Tossing a toy more than one foot away during play when it is not meant to be thrown.

These examples give the interventionist a concrete mental picture.

3. Non-Examples That Clarify What Should Not Be Counted

Non-examples are essential for avoiding accidental misreporting. They define the boundary line between relevant and irrelevant behavior.

Good non-examples:

• Show common look-alikes that don’t meet criteria

• Clarify contexts when the behavior is appropriate

• Prevent overcounting or inflating data

Example (Crying/Screaming):

Non-examples include:

• Crying after falling on the playground (injury-related).

• Laughing or playful yelling.

• Vocalizing loudly during music time when others are also loud.

These distinctions prevent confusion between skill deficits, environmental issues, typical development, or legitimate distress.

Why These Three Components Matter

An operational definition without one of these three components is incomplete. Here’s why:

✔ They increase interobserver agreement (IOA)

When multiple people collect data, their numbers should match. Clear definitions make that possible.

✔ They allow accurate progress monitoring

Interventions only work if you can measure change. Sloppy definitions = sloppy decisions.

✔ They prevent misinterpretation

Your staff, the school team, caregivers, and insurance reviewers all need the same mental picture.

✔ They support ethical practice

Precision protects learners from inappropriate treatment based on misinterpreted data.

Template You Can Use for Any Behavior

Here’s a repeatable structure you can include in the post:

[Behavior Name]

Definition:
A clear, observable, measurable description (1–2 sentences).

Examples include:

• Example 1

• Example 2

• Example 3

Non-examples include:

• Non-example 1

• Non-example 2

• Non-example 3

Onset: Describe how to identify the moment the behavior begins (optional but recommended for duration-based behaviors).

Offset: Describe how to identify the moment it ends.

Conclusion

Operational definitions are the backbone of accurate, ethical, and effective ABA practice. When you define behavior with precision—using observable descriptions, clear examples, and unmistakable non-examples—you give your entire team the tools to measure change consistently and confidently. Strong operational definitions reduce confusion, strengthen collaboration, and ensure that interventions are built on meaningful, trustworthy data.

Whether you're writing definitions for a formal FBA, designing a Behavior Intervention Plan, or supporting skill acquisition, your clarity directly drives learner success. As you refine your definitions, revisit them often, adjust them when staff ask questions, and sharpen them any time data doesn’t quite match what you’re seeing in session. Precision isn’t just a technical skill—it’s an act of compassion that helps every learner get the support they truly need.

References

Kubina Jr, R. M., Halkowski, M., Yurich, K. K., Ghorm, K., & Healy, N. M. (2022). Comparing the Detection Accuracy of Operational Definitions and Pinpoints. Journal of Behavioral Education, 1-21.

Peterson, L., Homer, A. L., & Wonderlich, S. A. (1982). The integrity of independent variables in behavior analysis. Journal of applied behavior analysis, 15(4), 477-492.

Ribes-Iñesta, E. (2003). What is defined in operational definitions? The case of operant psychology. Behavior and Philosophy, 111-126.