In the field of criminal investigation, it is quite common to get several descriptive contents not matching with one another. Due to our subjective perceptual and emotional abilities, as well as the exposure to post-event informations, our memory tends to be mistaken.
This last factor has been focused on for a few decades, especially by Elizabeth Loftus – who called the phenomenon misinformation effect (Loftus, Miller & Burns, 1978). It occurs in a situation in which an individual adds to his/her recall false informations. These are collected whether by suggestion or by the exposure to other sources of information related to the event he/she witnessed. Moreover, the individual tends to associate his claims with a true memory, and not with what he/she could have heard or seen after the event.
Of course, since this effect is quite an issue for the testimonies’ quality, Ginet and Py (2001) developped the cognitive interview, which notably contains a visual imagery task. Visual imagery is a cognitive activity that consists in building up an image of an object out of direct vicinity, whose properties are collected from semantic memory. The use of such an activity, according to Ginet and Py, has a positive effect on event-related free recall, especially if the images are vivid (i.e. close to a real perception).
However, the overall effect of visual imagery on the proportion of false memories is still in debate – mostly due to contradictory results (Gonsalves & Paller, 2000 ; Eisen, Gomes, Lorber & Uchishiba, 2013). Therefore, this study focuses on bringing new data on the subject, namely the impact of vivid mental imagery on a memory’s quality.
To do so, 69 participants viewed a 7-minute video cut showing an event from Costas Gavras’ (1969) « Z » movie. A misinformation paradigm, developed by Mahé (2013), has been presented, with an explicit imagery instruction given according to two conditions : one during misinformation and the other, a week later, during retrieval. A third group has not been given an imagery instruction. We measured the amount of correct recognitions depending on the three conditions. In order to determine each participant’s imagery abilities, we used Marks’(1973) Vividness of Visual Imagery Questionnaire (VVIQ).
Statistical analysis has shown a moderate effect of a visual imagery task on the amount of false recognitions based on the video cut. Besides, one’s high imagery ability compared with one’s low imagery ability proved to have no significant effect. Lastly, the median amount of correct recognitions is the same for both the conditions in which an imagery instruction has been given.
In other words, our experiments brought nothing absolutely significant about the introduction of a visual imagery activity in an event-related memory task. And it can be best explained on the basis of the Implicit Activation-Monitoring Theory (Roediger, Watson, McDermott, & Gallo, 2001 ; Gallo, 2010). A single information can activate a wide amount of concepts strongly bound to each other amidst a great network. It is the source-monitoring process’ role to discriminate between the simple result of the wide conceptual activation and what is relevant only to determine if the retrieved elements are parts of a true memory.
When false informations are added to the event by an external source, the similarity between them and the true memory’s components causes our source-monitoring processes to not be able to make a difference – which is a consequence of a false memory occuring.
Although this is the best we could provide to explain the results, let us keep in mind that they were moderately significant. To validate them, it may be necessary to sample our population according to their imagery ability, make the experiment individual and not collective – all to avoid communications and other interferences –, find a way to make sure the imagery instruction is observed, etc. This could, of course, be tried in further studies.
Bibliography
Eisen, M. L., Gomes, D. M., Lorber, W. G., Perez, C. I., & Uchishiba, H. (2013). Using an individual differences approach to examine two distinct types of suggestibility effects. Applied Cognitive Psychology, 27, 2-11.
Gallo, D. A. (2010). False memories and fantastic beliefs: 15 years of the DRM illusion. Memory and Cognition, 38(7), 833-848.
Ginet M., & Py J. (2001). A technique for enhancing memory in eye witness testimonies for use by police officers and judicial officials: the cognitive interview. Le travail humain, 64, 173-191.
Gonsalves, B., & Paller, K.A. (2000). Neural events that underlie remembering something that never happened. Nature Neuroscience, 3, 1316-1321.
Loftus., F., Miller, G., & Burns, J. (1978). Semantic integration of verbal information into visual memory. Journal of Experimental Psychology : Human, Learning and Memory, 4(1), 19-31.
Mahé, A. (2013). L’humeur induite, un facteur modulateur de la production d’illusions et de distorsions mnésiques chez le jeune adulte. Thèse de Doctorat, Université de Nantes.
Roediger III, H. L., Watson, M., McDermott, B., & Gallo, A. (2001). Factors that determine false recall : a multiple regression analysis. Psychonomic Bulletin and Review, 8(3), 385-407.
