Memory impairments are a core feature of the cognitive profile in schizophrenia. Among these deficits, illusions, confabulations, especially false memories are observed. False memories relate to either remembering events that never happened or remembering them quite differently from the way they happened (Roediger and McDermott,1995). This study intends to identify the cognitive mechanisms involved in creating false memory in patients suffering from schizophrenia. In order to fulfil this goal, we used the Deese-Roediger-McDermott paradigm (Roediger & McDermott, 1995) which is known to elicit strong false memories.
In this paradigm, participants were presented with series of words lists each semantically converging on one word that was not presented in the study lists: the critical lure. Studies that have used this paradigm demonstrated that healthy people as well as schizophrenic patients were often likely to recall and recognize the critical lure.
The main theory explaining the DRM phenomenon is the Activation-Monitoring Theory (AMT, Roediger, Watson, McDermott, & Gallo, 2001). This theory is based on spreading activation models (Collins & Loftus, 1975) and on the concept of source monitoring (Johnson, Hastroudi, & Lindsay, 1993). Briefly described, this theory considers that at encoding, words are activated in the semantic framework and this activation spreads and activates semantically linked concepts (e.g., critical lure). At the retrieval, participants are unable to distinguish false memories (critical lure, mentally activated) to veridical memories (learned word), this phenomenon is commonly named « failure in source monitoring ».
Previously published studies on false memories in schizophrenia are not consistent. In fact, several studies indicated that schizophrenic patients didn’t differ from healthy control on creating false memories. Conversely, others studies showed a diminished rate of false memories in patients compared to healthy participants. However, these controversial outcomes could be explained by a significant methodological variability in experiments.
Therefore, the aim of the present study was to know if false memories are more related to semantic or episodic memory’s impairment in schizophrenia. Conforming to evidence from deficits in these two kinds of long-term memory in schizophrenia, we supposed that patients retrieved less false memories and veridical memory than healthy people.
Eighteen participants were recruited in each group for the experiment. Several selection’s criteria were used (as sex; level of study; stabilized schizophrenic disease). On the whole, these participants were on average male, and 31 years old.
All participants were presented to a DRM paradigm which consists of 8 lists of 15 words. After each list, participants had to recall as many words as they remembered. Following this learning phase, a recognition test was conducted in which participants had to decide if words were presented during the learning phase (studied items) or not (distractors). Among distractors, critical lures and words that were not semantically related to studied words were presented. A false memory was defined by the erroneous recall or recognition of the critical lure.
Afterwards, patients’ performances in recall and recognition were compared with those of control participants. Our outcomes reveal a lower rate of veridical retrieval in patients compared to controls. More precisely these results were interpreted as impairment in strategic encoding process which impacts recollection1-based retrieval. However, no difference was found concerning the retrieval of critical lures (i.e., false memories). According to AMT, the present study reveals that false memories of patients (as well as controls) are consecutive to a preserved spreading activation in semantic network2 (at encoding) and a source monitoring failure (at retrieval). Nonetheless, it was found that the creation of false memories depends on the kind of tests used: patients with schizophrenia were more prone than controls to falsely recognize non-studied items which were not semantically associated. Moreover, patients recognized in the same extent studied and non-studied items (critical lures), whereas control participants recognized more studied items than critical lures. These results lead to several interpretations. On one hand, in recognition test patients could use a familiarity-based strategy to falsely recognize critical lures (i.e. patients recognized a similar rate of veridical and false memories because of their familiarity). On the other hand, they could use luck to recognize words. In fact, given their encoding deficits, during the recognition test, memories of studied items could be too much erased to lead the decision making.
To conclude, the current research highlights the importance of encoding deficits which seem to affect veridical and false memory of patients. Moreover, the results of this study support the idea that false memories are related to familiarity-based recognition and spreading activation in schizophrenia. Our outcomes, even if they remain to deepen, can allow a best comprehension of memory impairments in schizophrenia and could guide future cognitive remediation programs.
Key words: False memories, Schizophrenia, Familiarity, Activation-Monitoring Theory
Words I have learned:
To deepen : to make more profound (approfondir)
1Recollection : mechanism which allows us to consciously retrieve a memory (recuperation consciente)
2Semantic network : models of semantic memory in which semantic knowledge (general world knowledge) are linked each other according to the principal of semantic distance (reseau sémantique)
Fulfil : to do something to satisfy your objectives (atteindre)
Spreading activation : a mechanism by which the activation of a concept in semantic memory framework will propagate to adjacent concepts (propagation d’activation)
Bibliography :
Collins, A. M., & Loftus, E. F., (1975). A spreading-activation theory of semantic processing. Psychological Review, 82(6), 407–428.
Johnson, M. K., Hashtroudi, S., & Lindsay, D. S. (1993). Source monitoring. Psychological Bulletin, 114(1), 3–28.
Roediger, H. L., Watson, J. M., McDermott, K. B., & Gallo, D. A. (2001). Factors that determine false recall: A multiple regression analysis. Psychonomic Bulletin & Review, 8(3), 385–407.
Roediger, H. L., & McDermott, K. B. (1995). Creating false memories: Remembering words not presented in lists. Journal of Experimental Psychology: Learning, Memory, and Cognition, 21(4), 803–814.
Clarisse RENAUDIN, M2 PPCECC