Prior learning creates a framework for similar memories to be stored in close proximity to each other. This framework is known as a ‘schema’. One bit of evidence for this comes from a 2016 study on human semantic memory – long-term memories of ideas and concepts devoid of personal detail. To parse the terrain, researchers used functional magnetic resonance imaging (fMRI) to show that similar words are stored in adjacent regions of the brain, and even created a ‘semantic map’ of language in the human cortex. Another recent study confirmed that shared memory traces are organised in similar ways from one individual to the next.
Although we might think of memories as being strengthened when recalled, the truth is actually more complex. Recalling a memory reactivates the neurons composing the memory trace, spurring them to form new connections. The altered circuitry then becomes stable again, and the memory is ‘reconsolidated’.
Reconsolidation can reinforce learning over time by strengthening neural connections and allowing the formation of new associations.
But obviously, taking a memory trace apart and putting it back together again makes that memory vulnerable to losing its fidelity. Here’s an example: at some point in their education, most Americans learn that Alexander Hamilton was a founding father but not a US president. However, when a study on false memory investigated whom most Americans identify as US presidents, the subjects were more likely to incorrectly select Hamilton but not several actual former presidents. This is likely to be because neurons encoding information about Hamilton were frequently activated at the same time as neurons encoding information about former presidents. Because neurons that ‘fire together wire together’, a connection between past presidents and Hamilton could gradually become strong enough that you would incorrectly remember Hamilton as a former president himself.
The Hamilton study could also help to explain why groups of people share false memories, as with the mystery of Shazaam. First, there was a children’s movie called Kazaam (1996) starring Shaquille O’Neal as a genie. Then, some people falsely remember another 1990s film, perhaps a rip-off of Kazaam, called Shazaam, starring the comedian Sinbad as a genie. Although Shazaam never existed, there are hundreds of people online who claim to remember it.
There are several reasons for this. First, a large number of general associations increase the probability that a false memory could emerge. Twin films with similar concepts being released at around the same time were common in the 1990s. Sinbad had a different movie out that same year called First Kid, which – like Kazaam – involves the hero coming to the aid of a wayward boy. And Sinbad had also previously released Houseguest (1995), the poster for which has an image of his head coming out of a mailbox, perhaps abstractly resembling a genie emerging from a lamp. Sinbad is an Arabic name, and the story of Sinbad the Sailor is often associated with encounters with genies. Sinbad’s bald head and goatee resemble a typical genie portrayed in the media. Sinbad also dressed up like a genie for a movie marathon he hosted in the 1990s, which almost certainly contributed to the ‘memory’ of Sinbad playing a genie. Besides similar associations laying the groundwork for a false memory to form, the other main factors in this instance are confabulation and suggestibility.