There has been controversy to the limitations of the dual-coding theory. Dual-coding theory does not take into account the possibility of cognition being mediated by something other than words and images. Not enough research has been done to determine if words and images are the only way we remember items, and the theory would not hold true if another form of codes were discovered. Another limitation of the dual-coding theory is that it is only valid for tests on which people are asked to focus on identifying how concepts are related. If associations between a word and an image cannot be formed, it is much harder to remember and recall the word at a later point in time. While this limits the effectiveness of the dual-coding theory, it is still valid over a wide range of circumstances and can be used to improve memory.