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Verbal overshadowing exists when nonverbal experiences are verbally described, which in turn negatively affects recall of originally nonverbal experiences. Furthermore, the theory of perceptual symbol systems postulates that in verbal overshadowing, verbal descriptions are attached to nonverbal stimuli, and the resulting representation activates prototypes of the nonverbal stimuli. Therefore, upon recall of the stimuli, the person will retrieve a distorted memory that has been influenced by previous experience of stimuli in the same category and similar to the new stimuli perceived. The purpose of the current experiment is to empirically test the perceptual symbol system explanation for the verbal overshadowing phenomenon and control how nonverbal stimuli are learned. During the experiment, 25 participants viewed 36 visual stimuli or spy devices and verbally described each property of the device. Next they were shown 2 new devices, labeled CIA-99 and KGB-50, with properties that were different from the 36 devices that they were biased towards. Lastly, the participants were tested on the accuracy of their recall of the two new devices. Results support the hypothesis, which states that verbally describing properties of visual stimuli causes the formation and retrieval of average or prototypical property values for those stimuli. Participants recalled the biased or average visual stimuli rather than the correct visual stimuli. The researchers plan to continue study on the process of verbal overshadowing by manipulating various parts of the paradigm to further assess how well the perceptual symbol system theory can explain the verbal overshadowing phenomenon.
Background Information: A popular view is that knowledge of the world is based on concepts. Although we have novel experiences, these experiences are similar to previous experiences we have already encountered. Therefore, we form concepts or mental representations that correspond to that category or the class of objects in the world. The formation of concepts guide our interactions with anything in that category (Murphy, 2002). Researchers observed the modality specific process of retrieving memories when subjects recalled faces, color, musical segments, and wine tasting (Schooler & Engstler-Schooler, 1990 and Schooler, Fiore, & Brandimonte, 1997). Verbal overshadowing occurs when a nonverbal experience is described verbally. This, in turn, interferes with the accuracy of the subsequent recall of that nonverbal experience (Schooler & Engstler-Schooler 1990). However, researchers have not offered a detailed explanation for the phenomenon that is referred to as verbal overshadowing. Barsalou (1999) offered the Perceptual Symbol System Theoretical Account to explain the modality specific process of verbal overshadowing. The theory proposes that when a non-verbal stimulus is perceived, if a verbal description is attached, it will activate property and relation simulators or prototypical characteristics of the stimulus. Once simulators are activated, the prototypical simulations interfere with the retrieval of the stimulus that was presented. (Figure 1)
The Visual Stimuli
The spy devices consist of 4 properties:
• Antenna
• Low battery light
• Grip
• SOS button
Participants & Design Strategy
There were two versions of the basic experiment in which the visual stimuli was presented. Participants included 27 predominately right-handed Native English speakers. However, 2 participants were not used in the analysis. Therefore for analytical purposes, 13 participants completed Version 1 and 12 participants completed Version 2 of the basic experiment.
Procedure
In the basic experiment, participants were presented with visual stimuli labeled as spy devices. A cover story was attached to these spy devices in order to provide significance and motivate the participants to study these devices. There were three phases to the basic experiment which included: (1) the bias phase; (2) the study phase; and (3) the test phase. In the bias phase, the participants view 36 devices presented with either Level 1 or Level 3 property values (see Figures 2 and 3). In the study phase, the participants were presented with 2 devices with memorable names, the CIA-99 and the KGB-50. Both devices have a property value of Level 2, which is the value that participants have not seen before. Lastly, in the test phase, the predictions of the current study were tested by prompting the participant to recall their first, second, and third choice of the correct devices that were presented during the study phase. In the same manner, they also recalled properties of the devices presented in the bias phase to ensure the results.
Hypothesis
If participants use simulators to attribute a property to a concept, they should choose the device and the properties that contain the biased values. Results will support the perceptual symbol system theoretical account as a possible explanation of how verbal overshadowing effects the retrieval of holistic representations due to the experimental control of property and relation simulators.
In order to perform data analysis, each property and device was assigned a weight contrast value (Figure 4). The properties and values presented in the bias phase have a value of 1. The properties and devices (KGB-50 and CIA-99) presented in the study phase have a value of 0. The properties and values that were not viewed in either phase, but were an option to choose in the test phase have a value of -1. Next, in order to calculate each participant’s score, each choice rank was assigned to a contrast value (Figure 5). To calculate the score for each device and property, the weight contrast value is multiplied by the rank and each is added together. A score greater than 0 will support the hypothesis. The ideal score which would be congruent with the hypothesis is a score of 2. If participants choose the bias device/property that has a value of 1 as their first choice (also at value of 1), then the neutral device/ property as their second choice (values of 0 and 0 respectively), and lastly the device/property presented in the study phase as their last choice (values of 1 and 1 respectively), the equation is as follows: 1*1 + 0*0 + -1*-1 = 2 (Figure 6) The average scores for Version 1 and 2 illustrated in the chart show that, for each device probe, results support the hypothesis. (Figures 7 & 8) Average scores for each property of the devices.
Because participants’ average scores were significantly greater than 0, results support the perceptual symbol system explanation for verbal overshadowing. Further study and manipulation is needed to further assess the theory as a possible explanation.
This material is based upon work supported by the National Science Foundation Award under Grant No. 0450303 (Subaward # I-66-606-63 to Emory University) and Grant No. BCS-0212134.
Verbal overshadowing exists when we try to remember nonverbal things by describing them verbally. However, the verbal descriptions we use activate prototypes or averages of things that we have seen that are similar to the present stimuli. The perceptual symbol systems theoretical account is a theory that seeks to explain how the process of verbal overshadowing occurs. This experiment tested the perceptual symbol systems as a possible explanation for verbal shadowing as participants were presented with visual stimuli and asked to verbally describe them. At that stage, they formed prototypes of this type of stimuli. Afterwards, they were shown two novel stimuli and subsequently asked to recall them. As predicted, participants were not accurate in recalling the novel stimuli. Therefore the hypothesis was supported.
Presented visual stimuli on a computer using PowerPoint presentation
cognition, human subjects, questionnaire
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