Two kinds of verbal behavior plus a possible third.

Speaking, writing, and signing (American Sign Language) are types of verbal behavior where each different verbal relation involves a different topography. It is also possible to behave verbally by pointing at or in some way indicating the relevant verbal stimuli, where response topographies do not differ from one verbal relation to another. There are a number of potentially important differences between topography-based and stimulus-selection-based verbal behavior, although the two are often treated as equivalent from a behavioral as well as from a traditional perspective. Selection-based verbal behavior involves a conditional discrimination whereas topography-based verbal behavior does not. In topography-based, but not in selection-based verbal behavior, there is point-to-point correspondence between response form and relevant response product. Also, effective selection-based verbal behavior requires a good scanning repertoire whereas in topography-based verbal behavior the correct response simply becomes stronger under appropriate conditions. What is traditionally referred to as receptive language training is described as quite similar from a behavioral perspective to training in selection-based verbal behavior. Given the differences between topography- and selection-based verbal behavior, the wisdom of the current rather extensive reliance on selection-based verbal behavior in language instruction for developmentally disabled clients is seriously questioned.