Applied behavior analysts seek to change socially relevant behavior by manipulating the environment to make a behavior occur more or less often.
To do so, applied behavior analysts require two features of a behavior and make two assumptions about a behavior.
Behavior is individual
In applied behavior analysis (ABA) a feature of behavior is that ALL behavior is individual. People exhibit behavior. Even in groups, the groups do not behave, individuals within the groups behave.
Behavior is continuous
Another feature of behavior in ABA is that behavior is continuous meaning that behavior never stops and changes over time. All measures of behavior are simply reflections of a behavior in a given time period and behavior is always evolving as new functional relations are made.
Behavior is determined
An assumption made by applied behavior analysts is that behavior is determined by functional relations in the environment. A person does not choose to engage in a behavior with rational thought but because of learned behavior triggered by discriminating stimulus in the environment.
Behavioral variability is extrinsic to the organism
Another assumption made by behavior analysts is that if all behavior is determined by the environment, behavioral variability is caused by extraneous vectors in the environment.
For example, Tim goes on a walk with his mom every day and does not ever engage in eloping or tantrum behavior. One day Tim runs away from his mom and starts screaming on the walk. A behavior analyst would assume that Tim did not decide randomly that day to run away and scream but that something in his environment such as being tired, hungry, a dog barking, the sound of a truck backing up ect. Triggered the behavior.
These following features and assumptions are fundamental to what makes behavior analysts different from other practitioners. Although these are not facts and cannot be proven definitively, behavior analysts believe they are backed up with scientific data and evidence.
Cooper, J. O., Heron, T. E., & Heward, W. L. (2007). Applied Behavior Analysis (3rd Edition). Hoboken, NJ: Pearson Education.