Behaviour is a simple action that can be objectively measurable, such as verbal (using language) or motor (using the body), or not observable by others, also called “private events”, such as thoughts and feelings.
The scientific study of learning has three branches: philosophy of the science of behaviour, experimental analysis of behaviour, and behaviour modification.
Behaviour modification includes analyzing the relationship between environment and behaviour and changing the environment to help people modify their behaviour.
Ignoring the root causes of behaviour and just treating the antecedent causes is not a problem in behaviour modification, as antecedent causes are important; further root causes cannot always be determined anyway.
Ivan Pavlov (b.1849-d.1936) is known for his work on Conditioned Reflexes, which state that conditioned behaviours are involuntary; elicited by stimuli that precede them, forming a reflex.
Psychology in the 19th century was the scientific study of conscious experience, for example, introspection of the conscious experience of tasting lemonade.
B.F Skinner (b.1904-d.1990) awarded 1969 US National Medal of Science, developed operant behaviourism, the goal of which is to understand and explain all behaviour, including internal events.
Still others see behaviour modification as a separate category that includes: ABA (which is seen as applying only principles of operant conditioning), application of respondent (Pavlovian) conditioning, behaviour therapy, and behaviour therapy (treatment carried out on dysfunctional or maladaptive behaviour and thinking).