Short answer
This occurs because there are different types of memory, each relying on distinct processes in the brain. Learning to ride a bike is an example of 'procedural memory', which takes time to master. Remembering the 9/11 attacks is an example of 'episodic memory', which tends to be stored quickly and automatically.
Longer answer
Original question: ‘How is it possible that it takes so long to learn to ride a bike, yet I still exactly remember what I was doing during the attacks on the World Trade Center in New York on 11 September 2001? In other words, why is some information stored in our brain almost instantly, while other information takes so long?’
There are various types of memory, each dependent on different brain regions. Learning to ride a bike is an example of what scientists call ‘procedural memory‘. It involves learning to pedal, steer, and coordinate your body’s balance. This takes time because several areas of the left and right sides of your brain need to work together in a very precise way. Everything must be done with perfect timing; otherwise, you risk falling off and injuring yourself. Mastering all these minor adjustments requires considerable time and practice – and sometimes pain!
When you recall a specific event, such as the 9/11 attacks, this is called ‘episodic memory‘ – you are remembering a particular episode from your life. This type of memory is strongly influenced by the emotions you felt at the time. When an event has a significant emotional impact, such as the 9/11 attacks, it is often called a ‘flashbulb memory’. It is as though the flash of a camera captured the moment and permanently imprinted that memory in your brain. These highly emotional events – whether very negative or positive – tend to stay with us and can often be recalled in greater detail.
Imagine you fall off your bike one day and break your arm. The negative emotions tied to this would likely cause you to remember all the details of the event and the pain of your recovery for many years.
Why this occurs is still a key area of research. Some researchers believe that the emotions felt during an event make the memory more deeply embedded in our brain, much like a hot iron branding a mark into wood – the hotter the iron, the deeper the mark. Others suggest that it happens because emotions suppress memories of non-emotional experiences that occurred before or after the event, making the emotional experience stand out more. At the Donders Institute, we are conducting various experiments to investigate which of these explanations is most plausible.