This situation often occurs when we are trying to remember some event or the name of something. Often only the additional stimulation of the first letter will then bring forth the desired response, or perhaps some weak intraverbal supplementation will be sufficient. If we are in a zoo and see an aardvark, and we have previously learned the name but cannot remember it currently, someone may say, “The name begins with an ‘a’.” That may be sufficient to evoke the response. Notice that this would also be called a fragmentary echoic source of strength.
A type of controlling variable with the following features:
It sums with another controlling variable to evoke a response in a case of multiple controlling variables
The supplemental variable, by itself, is never likely to be sufficient to evoke the response
The type of controlling variable