Psycholinguistics is the study of how language is acquired, represented, and used by the human mind; it draws on knowledge about both language and cognitive processes. A central topic of debate in psycholinguistics concerns the balance between storage and processing. This debate is especially evident in research concerning morphology, which is the study of word structure, and several theoretical issues have arisen concerning the question of how (or whether) morphology is represented and what function morphology serves in the processing of complex words. Five theoretical approaches have emerged that differ substantially in the emphasis placed on the role of morphemic representations during the processing of morphologically complex words. The first approach minimizes processing by positing that all words, even morphologically complex ones, are stored and recognized as whole units, without the use of morphemic representations. The second approach posits that words are represented and processed in terms of morphemic units. The third approach is a mixture of the first two approaches and posits that a whole-access route and decomposition route operate in parallel. A fourth approach posits that both whole word representations and morphemic representations are used, and that these two types of information interact. A fifth approach proposes that morphology is not explicitly represented, but rather, emerges from the co-activation of orthographic/phonological representations and semantic representations. These competing approaches have been evaluated using a wide variety of empirical methods examining, for example, morphological priming, the role of constituent and word frequency, and the role of morphemic position. For the most part, the evidence points to the involvement of morphological representations during the processing of complex words. However, the specific way in which these representations are used is not yet fully known.