The Effect of Symbology on Iconic Memory
Marilyn Biddinger, Emily Musielewicz, Amanda Terrill
Alma College, Alma Michigan
marilynbiddinger@hotmail.com, emilymusielewicz@hotmail.com, mandyrynn@hotmail.com
The pioneering work of George Sperling (1960) was the starting point for the exploration of iconic memory. Sperling's classic experiment on the determination of iconic memory utilized a certain number of elements (letters) presented to subjects using a tachistoscope. The elements were presented in a grid-like formation for approximately 50 milliseconds and each subject was asked to recall as many elements as he/she could remember. This procedure is known as the whole-report procedure. Further, Sperling explored the ability to attend to certain aspects of the grid by performing the partial-report procedure (cited in Anderson, 1980) in which subjects were directed to a specific area of the grid by a high, medium and low tone sounded simultaneously with the presentation of the elements. Subjects were able to correctly identify the attenuated information in this experiment. The partial-report experiments have shown that while subjects can accurately recall attended information, some degree of unattended information is also processed. This led Sperling to conclude that some form of the presentation of the visual stimulation remains accessible for a brief time period after the presentation. The experimenters in this study have sought to explore the effects of a mixed-grid utilizing letters and symbols. The researcher's hypothesis states that symbols will have a greater degree of recall than letters in unattended stimuli.
METHOD
Participants.
The participants in this study consisted of 13 undergraduate college students, 8 females and 5 males.
Design.
Each participant was presented with twelve different 3x3 letter grids, eight containing only letters and four containing both letters and symbols. Four of the only letter grids served as practice exercises. A fix point was presented on the screen before each grid appeared. Slips of paper containing all letters and/or symbols presented in each grid mixed with random letters and symbols were created for participants to record their recall.
Apparatus and Stimuli.
The stimuli were presented by a Power PC Macintosh G3 computer through the Superlab program version 1.71. Images appeared as 3x3 letter grids in black font color on a white screen. The screen was approximately 212x165 mm and was positioned approximately 508 mm from the participants eyes.
The grid itself was approximately 2x2 inches and letters were presented in size 48 Verdana font. For the grids containing symbols, the symbols were presented in size 48 Webdings font. The fix point that appeared before every grid was also created using size 48 Verdana font. These grids and the fix points appeared in the direct center of the screen. Upon pressing the space bar, the trail grids would be presented on the screen for 60 ms. The slips of paper containing symbols and letters for the participant's recall were formed using the same fonts and sizes as used in the experiment.
Procedure.
Each participant sat in front of the computer screen and listened to the recorder give the instructions before starting the experiment. Participants were directed to look at the bottom line of the grid but to recall as much information as possible from the entire grid. The participants were presented with four practice trials before the actual experiment began. In each trial, the participant began by viewing the fix point. When they were ready for the grid to appear, they pressed the space bar and the grid flashed on the screen for 60 ms. The participant then recalled as many items from the grid as possible and circled what they could recall on the given sheet of paper containing letters and/or symbols from the grid and random letters and symbols. This sheet of paper was then immediately collected by the recorder. This process was repeated with all twelve trials.
RESULTS
The introduction of symbols did not yield an increase in the ability of subjects to recall elements but rather appear to have made the task slightly more difficult. The number of symbols correctly recalled by participants was approximately 2.8 compared to a 3.1 recollection rate for letters in unattended rows. (See Figure 1).
Figure 1. Number of Elements Recalled as a Function of Mixed Element Stimuli. The above information shows no significant increase in subject iconic memory due to the introduction of symbols.
DISCUSSION
It is apparent from the above data and previous research (Weichselgartner and Sperling, 1987) that the cognitive processes utilized in iconic memory for attended and unattended information occur simultaneously. The subject's recollection of either stimuli in the unattended rows, letters or symbols, demonstrates that these two events are concurrent. Research has shown (Weichselgartner and Sperling, 1987) that this occurs in two phases. The first phase is a quick, automatic process triggered by the attention direction. The second phase is a slower process that has shown a dependency on task difficulty. From this definition of the second phase, it is reasonable from the slightly lower number of symbols recalled, that symbols do not increase retention, but increase the task difficulty. Therefore, the hypothesis proposed by the experimenters proved incorrect. However, a more in depth study utilizing stricter experimental controls and a larger number of subjects is warranted.
REFERENCES
Anderson, J.R. (1980). Cognitive Psychology and Its Implications, Fourth Edition. Pgs. 85-87. New York: W.H. Freeman and Company.
Sperling, G.A. (1960). The information available in brief presentation. Psychological Monographs, 74, Whole No. 498. (Cited in Anderson - see above)
Weichselgartner, E. and Sperling, G.A. (1987). Dynamics of Automatic and Controlled Visual Attention. Science, 238, 778-780.
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