Older people struggle to remember important details because their brains cannot resist the irrelevant "stuff" they soak up subconsciously and as a result they tend to be less confident in their memories, a new study has found.
Researchers from Georgia Institute of Technology in the US looked at brain activity from Electroencephalography (EEG) sensors and saw that older participants wandered into a brief "mental time travel" when trying to recall details.
This journey into their subconscious veered them into a cluttered space that was filled with both relevant and irrelevant information, researchers said.
This clutter led to less confidence, even when their recollections were correct. Cluttering of the brain is one reason older people are more susceptible to manipulation, they said.
Researchers showed older adults (60 years and above) and college students a series of pictures of everyday objects while EEG sensors were connected to their heads. Each photo was accompanied by a colour and scene (for example, living room).
Participants were told to focus on one and ignore the other. An hour later, they were asked if the object was new or old and if it matched the colour and the scene.
Neither age group was very good at recalling what they were told to ignore. Both did well remembering the object and what they were supposed to focus on, researchers said.
"But when we asked if they were sure, older people backed off their answers a bit. They were not as sure," said Audrey Duarte from Georgia University of Technology.
Researchers noticed differences in brain activity between the young and old. Older adults' brains spent more time and effort trying to reconstruct their memories.
"While trying to remember, their brains would spend more time going back in time in an attempt to piece together what was previously seen. But not just what they were focused on - some of what they were told to ignore got stuck in their minds," said Duarte.
She uses a cocktail party as an example. Two older people are talking to each other. And even though they are only concentrating on the conversation, their brains absorb the other noise in the room.
"When it is time to remember the conversation, they may struggle a bit to recall some details. That is because their brains are also trying to decipher the other noises," said Duarte.
"What music was playing? What was the couple next to them saying? That extra stuff should not be in their memories at all, but it is. And it negatively impacts their ability to clearly remember the conversation," she said.
Younger people were quicker to recall details and used less brain power. The irrelevant information was never stored in the first place, which kept their memories relatively clutter-free, researchers said.
The findings were published in the journal Neuropsychologia.
