Nevertheless, the proper interpretation of these experiments (and all the other multifarious relevant laboratory findings) and thus the empirical status of Dual Coding Theory itself, remains controversial. Throughout its history, the theory has been developed and interpreted in the context of opposition to various forms of what have come to be known as common coding theories of memory: Theories committed to explaining all the relevant phenomena in terms of just one type of code (representational format) common to all memories. Thus, to properly understand Dual Coding Theory and the controversies that have surrounded it, it is important to be aware that the prevailing conception of the nature of this common code have changed quite radically over the course of the dual coding versus common coding controversy.