Encoding difficulty and memory: Toward a unifying theory

Past studies exploring the mnemonic benefits of encoding difficulty have produced inconsistent results. To explain these disparate results, we propose a framework that focuses on the type of processing that is induced by different difficulty manipulations, the nature of the learning material, and the importance of encoding both relational and individual-item information. Specifically, it is argued that a given difficulty manipulation will improve recall if it encourages processing of the type of information (i.e., relational or individual item) that is not encoded obligatorily from the material. Predictions from this framework were tested in two experiments in which different difficulty manipulations were performed on two different types of text. For descriptive texts, a difficulty manipulation that encouraged relational processing produced the highest recall. For fairy tales, recall was higher when subjects performed a difficult task that promoted the encoding of individual-item information. These results are explained in terms of the framework described above. Existing theoretical positions are also considered in light of the obtained pattern of effects.