The history of Behaviour Analysis goes as far back as 1913, the year in which John Watson defined all observable behaviour as psychology’s true subject matter. Watson introduced a new approach, in which he underlined the importance of environmental events in the control of all behaviour. Based on this new stimulus-response psychology, Watson started a movement called Behaviourism.

Later on, B.F. Skinner gave his own contribute to behavioural psychology by presenting a clear distinction between Ivan Pavlov’s classical conditioning  and his own concept of operant conditioning, showing that the future occurrence of a certain behaviour is largely determined by its consequences. Skinner and his colleagues introduced various fundamental principles of behaviour, which included concepts such as reinforcement, shaping, etc. These principles, used to describe how behaviour is lawful, observable, measurable and has an impact on the surrounding environment (pure science of behaviour analysis), were themselves adapted into a practical and applicable new field of psychology (applied behaviour analysis - ABA), which promoted the investigation of effective teaching methods.

One of the most influential applications of behaviour analysis occurred in the area of developmental disabilities. The necessities of individuals with learning difficulties combined perfectly with the developing area of ABA. ABA presented a comprehensive approach to the wide range of necessities those individuals with diverse developmental disabilities presented.

As time went by, many names in psychology turned their interests to behaviour. In the 1960’s Ivar Lovaas presented a comprehensive program, including a curriculum, the corresponding teaching sequence, and the principles and strategies for teaching. This later became to be known as “Lovaas intervention”. Originally, Lovaas’s way of applying behavioural analysis included the use of aversive stimuli, a means questioned by many. Later on, Lovaas restructured his application to exclude aversives. Never the less, the original application describes how to teach a target first in a clear and gradual manner (e.g. first in isolation, then with one and two distracters, followed by teaching another target the same way, and finally presenting the two in random rotation). Lovaas also emphasized the importance of intensity, table-time, eye contact, sitting calmly, etc. Independently of all the changes the original application undertook ever since, Lovaas’s program was pioneer in the application of behavioural analysis, especially to teach individuals with autism.

ABA proved to obtain amazing results with individuals diagnosed with autism. Lovaas himself started working with children whose behavioural repertoires presented many deficits of functional behaviour and many excesses of dysfunctional behaviour that, at the time, were labelled autistic. Lovaas applied basic behaviour analysis training procedures, which proved their effectiveness in this specific population. Lovaas’s true contribution was in the manner he applied these procedures - intensive 40 hours per week intervention rather than the traditional clinical psychology approach of only a 50 minute conversation per week.

In 1957, Skinner analyzed the functions of language and presented his conclusions in the book Verbal Behaviour (the book does not outline a method for applying verbal behaviour). Language was described in terms of its functions: mainly Mands, Echoics, Tacts, and Intraverbals. Applied behaviour analysts like Jack Michael, Vince Carbone, Mark Sundberg, James Partington studied Skinner's pure scientific analysis and applied it. Applied verbal behaviour is still applied behaviour analysis, except the focus is on the student's verbal behaviour.

Then, 30 years after Lovass started his revolutionary research, a woman – Catherine Maurice - had a little girl and then a little boy whose behavioural repertoires were so dysfunctional that they got labelled as autistic. After a first few desperate years, this mother finally found Lovaas’s ABA and with a lot of work and dedication on her part and on the part of Bridget Taylor, a behavioural therapist, the behavioural technology helped normalize her children’s behaviour. Having a PH. D. in literacy criticism influenced and served a personal desire of Catherine’s, to write probably the most important book in the field of autism, an autobiographical case study of her two children – Let Me Hear Your Voice.

Any human being will perform an action more often if it is certain of positive consequences (reinforcement), any person needs help and to be taught when they don’t know how to do something (prompting), such help needs to be removed gradually in order to create independency in performing the recently learned skill (fading), and abilities perfect themselves with practice (shaping). Behavioural science is solid and its application should be entirely based on the student. Through recorded data, personal experience and knowledge of the student, professionals should be able to determine what is more effective for each individual. Seeing that ABA’s intention is to change targeted behaviours, it is crucial to the success of the program that the targeted behaviours be chosen according to the students necessities and lifestyle, in a way that the change guarantees improvement to their quality of living.