The processes by which the human brain creates, stores, and uses memories are very complex and have been the topics of many research experiments in psychology. In 1972, Craik and Lockhart published a paper on levels of processing that suggested, “memory traces can be seen as records of analyses carried out for the purposes of perception and comprehension, and that deeper, more semantic, processing results in more durable traces” (Nyberg, 2002, p. 345). In the levels of processing model, there are three levels. The most shallow of these levels is the orthographic level, which is achieved by only visual cues. The middle level is the phonological level, which is achieved by auditory cues. Lastly, the deepest level is the semantic level, which requires thought about the meaning of the cue. Brain imaging studies have found that semantic processing is associated with increased activity in the left prefrontal regions of the brain, contrasted with lower levels of processing. One such study, performed by Kapur, Craik, and colleagues, had fMRI scans measure the brain activity of participants making semantic decisions. After a retention interval, the participants took a memory test. When correct recognition accompanied high confidence, increased activity was seen in the left prefrontal regions (Nyberg, 2002, p. 347). By looking at the physiological aspects of memory, researchers are able to learn more about how memory operates, and why some forms of processing result in more vivid and easily retrievable memories.
One method of studying the effects these levels have on memory is having participants engage in the three levels of processing, and then complete a memory task to see which levels yielded better results. Studies concerning the depth-of-processing (i.e., DOP) effects on memory show that levels of cognitive processing have predictable effects on performance in recall tasks (Boatright-Horowitz, Langley, & Gunnip, 2009, p, 331). Several research studies have shown that tasks requiring semantic processing result in greater recall ability. Wagner and colleagues conducted a study with 12 right-handed, participants who engaged in semantic processing, nonsemantic processing, and visual fixation tasks. Subsequent memory was much higher for semantic tasks (85% recognized) as opposed to nonsemantic processing (47% recognized) (Wagner, et al., 1998). These results appear accurate, because semantic processing requires thinking about the whole task in a conceptual way. Whereas, the orthographic level of processing only allows visual elements to be internalized, and the phonological level of processing only allows the internalization of auditory elements. Of the three levels, semantic processing involves the most effort, as it requires the most analysis of information. Therefore, it is logical that semantic processing yields better memory results.