Often seen as an adjunct to Applied Behavioural Analysis (ABA). Though both are based on theories developed by Skinner, there are differences in concept. In the late 1950s and early 1960s when Dr. Ivar Lovaas was developing his ABA principles, Skinner published Verbal Behaviour, which detailed a functional analysis of language. He explained that language could be grouped into a set of units, with each operant serving a different function. The primary verbal operants are what Skinner termed echoics, mands, tacts, and intraverbals.
The function of a mand is to request or obtain what is wanted. For example, the child learns to say the word "cookie" when he is interested in obtaining a cookie. When given the cookie, the word is reinforced and will be used again in the same context. There is an emphasis on function of language (VB) as opposed to form (Lovaas-based). In a VB program the child is taught to ask for the cookie anyway he can (vocally, sign language, etc.). If the child can echo the word he will be motivated to do so to obtain the desired object. In a Lovaas-based ABA program the child might say the word cookie when seeing a picture and is thus labelling the item. This form of language is called a tact. Critics of Lovaas say children are taught to label many words but often cannot use them in functional or spontaneous ways. Another operant, intraverbals describes verbal behaviour that is under the control of other verbal behaviour and is strengthened by social reinforcement. Intraverbals are the way people engage in conversational language. They are responses to the language of another person, usually answers to "wh-" questions. If you say to the child "I'm baking..." and the child finishes the sentence with "Cookies," that's an intraverbal fill-in. Also, if you say, "What's something you bake?" (with no cookie present) and the child says, "Cookies," that's an intraverbal (wh- question). Intraverbals allow children to discuss stimuli that aren't present, which describes most conversation and is a goal of Verbal Behaviour Intervention.
Both ABA and VB use similar formats to work with children. It is said that VB attempts to capture a child's motivation to develop a connection between the value of a word and the word itself. Many therapists are now using techniques of VB to bridge some of the gaps seen in ABA.