Our ability to selectively forget distracting memories is shared with other mammals, suggests new research from the MRC Cognition and Brain Sciences Unit (MRC CBU),  University of Cambridge. The discovery that rats and humans share a common active forgetting ability – and in similar brain regions – suggests that the capacity to forget plays a vital role in adapting mammalian species to their environments, and that its evolution may date back at least to the time of our common ancestor.

The human brain is estimated to include some 86 billion neurons (or nerve cells) and as many as 150 trillion synaptic connections, making it a powerful machine for processing and storing memories. We need to retrieve these memories to help us carry out our daily tasks, whether remembering where we left the car in the supermarket car park or recalling the name of someone we meet in the street. But the sheer scale of the experiences people could store in memory over our lives creates the risk of being overwhelmed with information. When we come out of the supermarket and think about where we left the car, for example, we only need to recall where we parked the car today, rather than being distracted by recalling every single time we came to do our shopping.

Previous work by Professor Michael Anderson at the MRC CBU, University of Cambridge, showed that humans possess the ability to actively forget distracting memories, and that retrieval plays a crucial role in this process. His group has shown how intentional recall of a past memory is more than simply reawakening it; it actually leads us to forget other competing experiences that interfere with retrieval of the memory we seek.  

“Quite simply, the very act of remembering is a major reason why we forget, shaping our memory according to how it is used,” says Professor Anderson.

“People are used to thinking of forgetting as something passive. Our research reveals that people are more engaged than they realise in actively shaping what they remember of their lives. The idea that the very act of remembering can cause forgetting is surprising and could tell us more about people’s capacity for selective amnesia.”

While this process improves the efficiency of memory, it can sometimes lead to problems. If the police interview a witness to a crime, for example, their repeated questioning about selected details might lead the witness to forget information that could later prove important.

Although the ability to actively forget has been seen in humans, it is unclear whether it occurs in other species. Could this ability be unique to our species, or at least to more intelligent mammals such as monkeys and great apes?

In a study published today in the journal Nature Communications, Professor Anderson together with Pedro Bekinschtein and Noelia Weisstaub of Universidad Favaloro in Argentina, has shown that the ability to actively forget is not a peculiarly human characteristic: rats, too, share our capacity for selective forgetting and use a very similar brain mechanism, suggesting this is an ability shared among mammals.

The full paper can be read here: Bekinschtein, B, et al. A Retrieval-Specific Mechanism of Adaptive Forgetting in the Mammalian Brain. Nature Comms; 7 Nov 2019; DOI: 10.1038/s41467-018-07128-7 

University of Cambridge – full press release 

For further information please contact Mike Anderson