Why does the Misinformation Effect occur?
There is a general acceptance, supported by research, for the misinformation effect: The introduction of misleading postevent information will impair the memory of an original event (Toland, Hoffman & Loftus, 1991). However, although this phenomenon is well-established its interpretation is not. This debate about why the misinformation effect occurs relates to a fundamental issue about human memory - whether or not memory traces are permanently stored.
Two of the mechanisms which have been offered to explain the misinformation effect are: the alteration hypothesis and the coexistence hypothesis (Toland et al., 1991). Both hypotheses share the assumption that the presentation of misinformation interferes with the original memory (referred to as memory impairment) and that this creates the erroneous reports given. The difference is between the types of interference that occur and the conclusions drawn regarding retrieval of an original witnessed memory.
The Alteration Hypothesis
This hypothesis takes the view that the misleading information actually alters the original memory traces. Support for this hypothesis comes from the inability to recover original memories after being presented with misleading postevent information.
This is the interpretation adopted by Loftus and colleagues who propose that the misleading information "overwrites" or replaces the original information so that it becomes destroyed. This results in the suggested information becoming an inseparable part of the original event memory.
The Coexistence Hypothesis
This hypothesis takes the view that the original information and the misleading information coexist in memory. This means that the original information is still there but it becomes inaccessible. Support for this hypothesis comes from "successful attempts to recover the original information after exposure to misinformation has...