FCT, or Functional Communication Training, is a widely used technique in Applied Behavior Analysis (ABA) that teaches a person to replace challenging behaviors with an appropriate way to communicate the same need. If a child throws a tantrum to get a toy, for example, FCT teaches them to ask for the toy instead. The core idea is simple: the challenging behavior is already communicating something, so give the person a better, safer way to say it.
How FCT Works
Every challenging behavior serves a purpose. A child might hit, scream, or destroy objects because doing so gets them attention, access to a preferred item, a break from a difficult task, or relief from something uncomfortable. FCT starts by identifying that purpose through a process called a functional assessment. Once the therapist understands why the behavior is happening, they teach a replacement behavior that serves the exact same function.
The replacement doesn’t have to be spoken words. It can be a gesture, a sign, a picture card, or a button on a speech-generating device. What matters is that the new communication is something the person can do reliably and that the people around them will recognize and respond to. For a child whose verbal skills are still developing, a visual cue card they can hold up is often more practical than expecting full sentences right away. As their language grows, spoken words can gradually take over.
Once the replacement communication is chosen, the therapist reinforces it consistently. Every time the child uses the new skill, they get what they were looking for. At the same time, the old challenging behavior no longer produces that result. Over time, the child learns that the new way of communicating works better and faster, and the problem behavior loses its purpose.
What Behaviors FCT Addresses
FCT is used for a wide range of challenging behaviors. On the severe end, it targets aggression, self-injury, and property destruction. But it’s also effective for less intense behaviors like wandering off task, pulling an adult by the hand instead of making a request (sometimes called “autistic leading”), or engaging in rigid, repetitive routines that interfere with daily life. The common thread is that all of these behaviors are doing something for the person, and FCT provides a socially acceptable alternative that accomplishes the same thing.
Why It’s Considered Highly Effective
FCT has one of the strongest evidence bases of any behavioral intervention. Function-based interventions like FCT typically reduce destructive behavior by at least 90%, and research consistently shows they outperform behavioral treatments that aren’t guided by a functional assessment. That 90% figure comes from decades of replicated studies, making FCT a go-to strategy for behavior analysts working with children and adults alike.
That said, real-world results depend on how well the intervention is implemented and maintained. In studies examining long-term outcomes with schedule thinning (more on that below), about 43% of cases achieved a 90% or greater reduction in destructive behavior, and 64% achieved at least an 80% reduction. These numbers reflect the messier reality of sustaining results over time, which is why the steps after the initial teaching phase matter so much.
Moving From Practice to Real Life
In the early stages of FCT, the replacement communication is reinforced every single time. If a child uses a picture card to ask for a break, they get a break immediately, no exceptions. This continuous reinforcement builds a strong connection between the new skill and the desired outcome. But real life doesn’t work that way. A teacher can’t always stop class the moment a child makes a request, and a parent in a grocery store can’t always hand over a snack on demand.
This is where schedule thinning comes in. Gradually, the therapist introduces small delays between the request and the reinforcement. These might start at just one second and slowly stretch to longer intervals. The child learns that making a request still works, but sometimes they need to wait briefly. The therapist, the family, and sometimes the child collaborate to set a starting point, a target schedule, and how quickly to move between the two.
Some programs also teach what’s called delay and denial tolerance. This involves teaching the child to respond calmly when told “not right now.” The child might practice saying “okay” after hearing a denial, and then gradually learn to wait through longer delays before getting what they asked for. This step is critical for making FCT work in classrooms, homes, and community settings where immediate reinforcement isn’t always possible.
Another approach uses visual signals to help the child understand when reinforcement is available and when it isn’t. A green card might mean “you can make a request and I’ll respond right away,” while a red card signals that requests won’t be fulfilled at the moment. Over time, the periods without reinforcement get longer, and the child learns to read environmental cues about when to communicate and when to wait.
Generalizing the Skill
One of the biggest challenges with FCT, especially for children with autism, is making sure the new communication skill transfers beyond the therapy room. A child might learn to use a picture card perfectly with their therapist but revert to old behaviors at school or with a grandparent. People with autism often have difficulty generalizing skills to new people, new settings, and new materials, so this has to be planned for deliberately rather than assumed.
Practitioners address this by moving instruction into natural environments as early as possible. Instead of only practicing in a clinic, the therapist might work with the child at home, in the classroom, or during community outings. Training caregivers, teachers, and other adults in the child’s life to respond consistently to the replacement communication is equally important. If the picture card works with the therapist but gets ignored by a substitute teacher, the child quickly learns that the old behavior is more reliable in that setting.
A Practical Example
Consider a child named Mark whose verbal communication is still developing. He bites his peers and throws tantrums when he wants a toy another child is using or when he’s stuck on a difficult activity. A functional assessment reveals that both behaviors serve the same purpose: getting help obtaining something he wants.
Because Mark’s speech isn’t yet reliable enough to be his primary communication tool, his team starts with cue cards he can hold up to request help getting a toy or completing a hard task. Every time he uses a card, an adult responds immediately. At the same time, tantrums and biting no longer produce the desired result. Mark also practices pairing the cards with spoken words, building toward verbal requests over time. The outcome: Mark stops biting his peers and throwing tantrums, using the cards and emerging speech to get his needs met instead.
This progression from a simpler communication form to a more complex one is typical in FCT. The first priority is giving the person something that works right now. As their skills develop, the communication method can evolve with them.