Memory for pictures and words as a function of level of processing: Depth or dual coding?

The experiment was designed to test differential predictions derived from dual-coding and depth-of-processing hypotheses. Subjects under incidental memory instructions free recalled a list of 36 test events, each presented twice. Within the list, an equal number of events were assigned to structural, phonemic, and semantic processing conditions. Separate groups of subjects were tested with a list of pictures, concrete words, or abstract words. Results indicated that retention of concrete words increased as a direct function of the processing-task variable (structural < phonemic <semantic). However, for both abstract words and pictures, phonemic and semantic processing produced equivalent memory performance. These data provided strong support for the dual-coding model.