Many of us learn how to ride a bicycle at a young age. As we grow older, we may stop riding-most of us go to school by bus or by subway. But whenever we get on a bicycle, ifs like we've never stopped biking.
This is strange. In many other cases, our memories let us down. We often find it hard to remember the name of a person or a place, don't we? So, why can we still ride a bicycle after we stopped riding a long time ago?
It turns out that there are many types of memory. They are stored in different regions of our brains. Memories of experiences (e. g, our first day at school) and of factual knowledge (e. g. , the capital of France) are called declarative (陈述的)memories. These memories can be communicated to others. Skills such as playing an instrument or riding a bike： are called procedural(程序的)memories. These memories are responsible for our performance.
Scientists have done many experiments on different memory types. Perhaps the most famous of them was carried out on Henry Gustav Molaison, an epileptic (癫痫患者). In an operation in the 1950s, part of his brain was taken away. After that, the man suffered less- from epilepsy. But there was a new problem-he couldn't remember things!
What went wrong with Molaison's memory system? Through various tests; scientists found he could learn new skills (slowly, though). However, he could never remember having been trained to learn a new skill. In other words, Molaison could develop new procedural, but not declarative, memories.
Scientists have concluded that even with serious brain injuries, procedural memories last much longer. However, they haven't yet found out why. Some say procedural memories are more lasting because they are stored in the brain's center.
Now, "just like riding a bicycle55 has been used as an idiom (习语). Can you guess its meaning? Yes, people use it to describe a skill that, once learned, is never forgotten.
