In recent years, the study of memory has been the subject of discussions among those researchers who try to identify the mechanisms and contents of memory and those who concentrate in discovering their functions. These two approaches differ not only in the theoretical explanations that they offer to some phenomena, but also in which phenomena they consider worth pursuing and how and where these phenomena should be studied (Bruce, 1991; Koriat & Goldsmith, 1996). From the late sixties on, the predominant line of research focused on the mechanism of memory. This approach was greatly influenced by the computer methaphor (Atkinson & Shiffrin, 1968) and by the emergence of the symbolic paradigms in psychology and cognitive science (Newell & Simon, 1972). Although, the theories within this approach differ, they share a basic principle: Human cognitive functioning is the result of a general purpose symbolic system, that is, of a system that manipulates symbols. (Newell, 1981; Newell & Simon, 1972). This principle implies there are cognitive structures where the symbols are stored and that there are processes to manipulate the symbolic structures. When applied to memory, this basic principle translates into the search for independent memory structures, into the study of the contents of memory (memorial representations and memory traces), and into the investigation of the basic mechanisms by which encoding and retrieval of stored symbols occur. The basic methodological approach involves quantifying the level of recall or the time to activate or recover a memory trace (Koriat & Goldsmith 1996).