Applied behavior analysis (ABA) formally emerged in 1968, when researchers at the University of Kansas published the first issue of the Journal of Applied Behavior Analysis and laid out the principles that defined the field. But the intellectual roots stretch back three decades earlier, and the profession as most people encounter it today didn’t take shape until the late 1990s. Understanding when ABA “started” means tracing a line from laboratory rat experiments in the 1930s to a field that now certifies over 81,000 practitioners worldwide.
The Laboratory Foundation: 1930s and 1940s
ABA’s theoretical backbone comes from B.F. Skinner’s 1938 book, The Behavior of Organisms. Working primarily with rats and feeding responses, Skinner drew a distinction between two types of behavior: respondent behavior, which is triggered by a known stimulus (like flinching at a loud noise), and operant behavior, which occurs without an obvious trigger and is shaped by its consequences. That second category, operant behavior, became the engine of everything ABA would later build on.
Skinner’s key insight was that behavior could be systematically strengthened through reinforcement or weakened through extinction. He described a “reflex reserve” that builds up during conditioning and depletes when reinforcement stops. These weren’t just abstract ideas. They were testable, measurable, and reproducible in controlled settings. For the next two decades, researchers refined these principles in laboratories, studying how timing, frequency, and type of reinforcement changed behavior in predictable ways.
From Lab to Real World: The 1960s
The leap from animal laboratories to human applications happened in the 1960s, and the University of Kansas was the epicenter. The Department of Human Development and Family Life, transformed in 1964 into an applied behavioral science department, assembled what would become one of the largest and most productive behavior analysis faculties in the world. Two founding faculty members, Donald Baer and Montrose Wolf, were central figures in pushing Skinner’s laboratory principles into classrooms, hospitals, and homes.
In the spring of 1968, Baer, Wolf, and their colleague Todd Risley published a paper titled “Some Current Dimensions of Applied Behavior Analysis” in the very first issue of the Journal of Applied Behavior Analysis. That paper essentially defined what the field was: the systematic application of behavioral principles to socially significant problems, with built-in measurement to confirm that the intervention, not something else, caused the change. The first issue also included studies on teacher attention and study behavior, techniques for increasing participation among psychiatric patients, and new approaches to education. This was the moment ABA had a name, a journal, and a working definition.
Why “Behavior Modification” Became ABA
Before the term “applied behavior analysis” caught on, most people called this work “behavior modification.” The name change wasn’t cosmetic. Behavior modification implied simply changing unwanted behavior, often through external control, without necessarily understanding why the behavior existed in the first place. Applied behavior analysis represented a more complete approach: practitioners sought to understand the function of a behavior, what reinforcement history was maintaining it (attention-seeking, escape from demands, sensory stimulation, or access to preferred activities), and how to replace it with a more appropriate alternative.
This shift also reflected a move away from only targeting behaviors you could see on the surface. Behavior analysts began considering internal experiences and private events as legitimate parts of the picture, broadening the field’s scope beyond its earliest, more rigid boundaries.
The Autism Connection: 1970s Through 1990s
ABA’s most widely known application, intensive therapy for children with autism, developed over a 15-year stretch of research led by Ole Ivar Lovaas at UCLA. By 1987, Lovaas published a landmark study involving 40 children who each received several hundred individually tailored treatment programs. The results drew enormous attention: nine of the children showed no diagnosable autism at the end of treatment, and eight of those maintained typical functioning throughout elementary school. The children made lasting gains in intellectual, social, emotional, and educational skills.
This study became one of the most cited pieces of evidence for intensive early intervention and drove much of the public demand for ABA services. It also sparked decades of debate about treatment intensity, methodology, and how to measure success, debates that continue today. But in practical terms, the Lovaas research was the catalyst that moved ABA from an academic discipline into a mainstream therapeutic service that families actively sought out.
Professional Certification: 1998 to Present
For its first three decades, ABA had no unified credentialing system. Individual states handled certification independently, if they handled it at all. That changed in 1998, when Gerald Shook founded the Behavior Analyst Certification Board (BACB). Shook had helped build Florida’s state certification program and saw the need for a national standard. He started the BACB as its sole, unpaid employee.
The growth since then has been staggering. From one person in 1998, the BACB grew to over 100 full-time employees by the end of 2022. The number of certified practitioners tells an even more dramatic story: as of 2025, over 81,500 people hold BACB certification worldwide. That expansion was driven largely by insurance mandates requiring coverage for autism treatment, which created massive demand for credentialed behavior analysts.
A Timeline in Brief
- 1938: Skinner publishes The Behavior of Organisms, establishing the operant conditioning principles that ABA is built on.
- 1964: The University of Kansas builds its applied behavioral science department, gathering the researchers who would define the field.
- 1968: The Journal of Applied Behavior Analysis publishes its first issue, giving the discipline its name and formal identity.
- 1987: Lovaas publishes intensive early intervention results for children with autism, connecting ABA to its most prominent application.
- 1998: The BACB is founded, creating a national certification standard for practitioners.
So the answer depends on what you mean by “start.” The science behind ABA dates to 1938. The field was formally named and defined in 1968. And the profession as families and insurance companies know it today took shape in the late 1990s, when certification standards and autism research converged to create the massive service industry that now exists.