A notable exception can be found in the work of Okado and Stark (2005), who examined true and false memories in the context of a misinformation experiment and thus studied richer false memories. Misinformation studies show how readily memory can become skewed when people are fed misinformation (Loftus, 2005). A typical misinformation study uses a simple three-stage procedure: subjects see a complex event, such as a simulated automobile accident; half the subjects receive misleading information about the accident, and the other half get no misinformation; and finally, all subjects try to remember the original accident. In one study that used that procedure, subjects saw an accident, and some of them later received misinformation about the traffic sign at the intersection in question. The misled subjects got the false suggestion that the stop sign that they had actually seen was a yield sign. When asked later what kind of traffic sign they remembered seeing, those who had been given the false suggestion tended to adopt it as their memory and claimed to have seen a yield sign. Hundreds of similar studies show that misinformation can change a person’s recollection in predictable ways.
In an fMRI study that compared true memories with false memories created by misinformation, some group differences emerged (Okado et al., 2006). For example, the true-memory reports were associated with greater activation in the visual cortex, whereas the false-memory reports were associated with greater activation in the auditory cortex. However, the overwhelming impression from the research is that true and false memories are activating similar portions of the brain and that a particular memory cannot be reliably classified as true or false.
Richard McNally and his collaborators (McNally, 2003) studied people who had very rich, although likely false, memories of alien abduction have been studied. One study explored whether people who believe they have been abducted exhibit heightened physiological reactivity (heart rate and skin conductance) that occurs commonly in patients who have posttraumatic stress disorder (PTSD) when they think about their traumas. The “abductees” studied had experienced apparent sleep paralysis and hypnopompic hallucinations, which are vivid dreamlike hallucinations that occur as one is waking up, such as seeing figures hovering near their beds. Most had recovered memories with such techniques as guided imagery and hypnosis. Some of the recovered memories involved sexual intercourse with aliens or having sperm extracted for breeding purposes. Their physiological reactions were similar to those seen in PTSD patients who listen to audiotaped scripts of their traumas. Thus, expressed emotion is no guarantee that a memory is true.
There is a further concern in the true-memory–false-memory distinction: In many of the real-world cases, there have been attempts to get people to remember, to discuss their memories, to imagine details, and so on. Those very attempts can increase the detail and vividness of false memories—the very characteristics that lead (or rather mislead) people to believe that the memories are real.