3.2.3 Verbal and Imaginal Representation in Memory

"A picture is worth a thousand words." Although the validity of this aphorism may be debatable, there is little doubt that we humans have extraordinary capabilities for remembering information about visual events. There is little doubt that pictorial information can be represented in our memories quite well. Certainly, our subjective experiences would tell its so. Most of us easily can conjure up an image of a book, a soaring bird, a train wreck, or a walk in the woods.

One of the main contributions of cognitive psychology has been a revitalization of interest in the study of mental imagery. Once largely banished from experimental psychology as subjective, mentalistic, and therefore unscientific, imagery has become a significant feature of the work of a number of cognitive psychologists.

One such psychologist, Alan Paivio, has proposed that information can be represented in two fundamentally distinct systems, one suited to verbal information and the other to images. The verbal coding system is adapted for linguistically based information and emphasizes verbal associations. According to Paivio, words, sentences, the content of conversations, and stories are coded within this system. In contrast, nonverbal information is stored within the imaginal coding system. Pictures, sensations, and sounds are coded here.

Paivio's theory has been called a dual coding theory, in that incoming information can be coded within one or both of the systems. Although the systems are separate, they are strongly interconnected in their impact on the recall ability of information. To the extent that information can be coded into both systems, memory will be enhanced, whereas information coded only in the verbal system or imaginal system will be less well recalled. In Paivio's view, the verbal and nonverbal codes basically are functionally independent and "contribute additively to memory performance". Paivio also hypothesizes that nonverbal components of memory traces generally are stronger than verbal memories.

Much of Paivio's early work was devoted to demonstrating the effects of the abstractness of materials on its memorability and relating these results to dual coding theory. For instance, some words (bird, star, ball, and desk) have concrete referents and presumably are highly imaginable. Thus, when presented with such words, both the verbal (e.g., the linguistic representation of the word bird, its pronunciation, its meaning) and the imaginal (an image of a bird soaring) representations are activated simultaneously. Other words, however, are more abstract and far less readily imaginable (e.g., aspect, value, unable). These words, although they activate the verbal coding system, are hypothesized to activate the nonverbal system only minimally. In Paivio's view, memory for abstract materials should be poorer since such materials are represented only within a single system. Pictures, since they tend to be automatically labeled, should be more memorable than words because, although pictures are automatically labeled (and hence dual‑coded), words, even concrete ones, are not necessarily automatically imaged.

In a large number of studies, Paivio and his associates have dem­onstrated the beneficial effects of imagery on learning and memory, consistent with his predictions. Words rated high in imagery have been shown to be better remembered in free recall, in serial learning (where a series of words must be recalled in order), and in paired‑associate learn­ing (in which the "associate" of a word must be recalled when the word is presented). Similarly, instructions to subjects to "form images" also have been shown to enhance memory.