Levels of Processing: The Effects of Orthographic, Phonologic, and Semantic Processing on Memory

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.

The premise that semantic processing yields better recall abilities is the focus of this experiment; executed by Dr. Alan Swinkels of St. Edward’s University in Austin, TX. In order to see the extent to which semantic processing improves recall capabilities, the experiment compared semantic processing with the other two levels of processing, phonological and orthographic. For this experiment, participants had to follow certain instructions that involved making judgments about words. These judgments created the different levels of processing. Counting the number of vowels in a word made the participants engage in orthographic processing, counting the number of syllables in a word made the participants engage in phonological processing, and deciding the pleasantness or unpleasantness of the word made the participants engage in semantic processing. It was predicted that the words the participants made semantic judgments about would be the most memorable to the participants. These results were expected because several studies have shown that semantic processing yields better recall results.

Method

Participants

This repeated measures design involved 19 participants from an upper level psychology course at St. Edward’s University. The participants consisted of 3 men and 16 women; all participants were between the ages of 18 and 22. The participants completed the experiment as a class requirement, and there were no dropouts during the course of the experiment.

Materials

An automated PowerPoint with 54 cue slides, 54 word slides, an introduction slide, and an ending slide was used. Each cue letter slide was presented for exactly three seconds, and every word slide was presented for exactly five seconds. The slides had a solid color background, with the word or cue letter positioned in the middle of the slide without distractions surrounding the word or cue letter.

Design

This experiment was a repeated measures design, with one independent variable that had three levels. The independent variable was the depth of processing the participants engaged in. The levels of the independent variable were the three levels of processing: orthographic, phonological, and semantic. Every participant received a response sheet that had instructions on the top portion, followed by 54 response spaces organized into three columns of 18 response spaces. The three cue letters used were A, B, and C. These cues signaled the participants to count the number of vowels (orthographic processing), count the number of syllables (phonological processing), or indicate whether the word was pleasant or unpleasant (semantic processing).

To eliminate specific item effects, there were three different sets of instructions that all had the same cue letters and processing instructions, but in different orders. So, for 1/3 of the participants the “A” cue could mean engaging in the semantic level, whereas for another 1/3 of the participants it could mean engaging in the orthographic level. Every word in the study was used for every level of processing by the three groups. There were three forms of the response sheet, and the sheets were coded with a Roman numeral I, II, or III in the bottom right corner to distinguish which response group the sheets belonged to.

Each cue letter group contained an equal number of words, because having unequal numbers in the conditions could have affected the recall of the participants. Each condition was randomly assigned 18 words, and no theme or commonality was present within the condition groups. All words used were common nouns of a low reading level.

This experiment used a randomized block design to control for order effects. The 54 words were divided into 18-word groups (different than the condition groups), and within each group there were six randomly selected A, B, and C words. The order of the A, B, and C words was randomly assigned within the groups. By taking this precaution, it assured that there would not be a grouping of one type of word, especially towards the end, which might affect the recall of the words.

Procedure

Each participant randomly received one of the three forms of the response sheet. After distributing the sheets, the researcher gave a verbal explanation of what the participants were expected to do, and allowed questions to be asked. The experimenter explained that the experiment was automated and, once started, would run to completion. During the experiment, a cue letter was shown for three seconds. Depending on the instructions on the response sheet, the cue letter prompted the participants to count the number of vowels in the word, count the number of syllables in the word, or state whether the word was pleasant or unpleasant. The word appeared directly after the cue letter and was displayed for five seconds, giving the participants enough time to think about and record their answers on the response sheet in the spaces provided. After the display of the 54 cue letters and words, the participants completed a 30 second distracter task.