AMES, Iowa – A series of studies conducted by an Iowa State University research team shows that it is possible to manipulate an existing memory simply by suggesting new or different information. The key is timing and recall of that memory, said Jason Chan, an assistant professor of psychology at Iowa State.
“If you reactivate a memory by retrieving it, that memory becomes susceptible to changes again. And if at that time you give people new contradictory information, that can make the original memory much harder to retrieve later,” Chan said.
One of the major findings from the studies, published in the latest issue of Proceedings of the National Academy of Sciences, is the impact on declarative memory – a memory that can be consciously recalled and verbally described, such as what you did last weekend. The effects are powerful because people are retrieving memory and then incorporating new information. Chan and Jessica LaPaglia, a graduate student at Iowa State, tested the impact of new information when presented at different time intervals after the retrieval of the original memory.
If it was immediate, the memory could be altered. However, there was no effect on the original memory when the information was presented 48 hours later. Chan said based on other studies, it appears there is a six-hour window before the memory is reconsolidated after recall and cannot be altered. Likewise, they found no effect if the information was presented in a different context than the original memory.
“During that reconsolidation period, that’s when the memory is easy to be interfered with. Once that window closes and that memory is stable again, if you get new information it should not interfere with that original memory,” Chan said. “We found support for that idea in a number of experiments in which we varied the delay between the interfering memory or the misinformation and when people took that initial test.”