sentences:  The researchers argue that these processing systems function much like Darwin's natural selection theory in that the "fitness" of a species and the "depth of processing" in the levels of processing cannot fully predict the final outcome, meaning the survival and retrievability of the species or the information processed.They have found that TAP is still vulnerable to this same type of circularity because it lacks a precise and definite definition.Basically, TAP can only be identified as happening only AFTER retrieval has occurred.