Mickayla Jope, of Green Island School, asks :-

Why do we only use 20 per cent of our memory?

Cliff Abraham, a psychologist at the University of Otago, responded.

You often hear it said that we use only 20 per cent of our memory or, for example, only 10 per cent of our brain. These statements are simply not true.

Our brains don’t store memories like putting books on the shelves of a library, or by storing files into the memory of a computer. In these cases you can measure how much memory storage space or bookshelf space is used, and calculate how much unused space is left.

Memories, however, are stored in a very complex fashion in the brain. Many nerve cells in many parts of the brain are involved in storing memories. It is likely that the same nerve cells can even participate in storing many memories.

One complication is that memories are not separate things, like library books. A single memory includes many kinds of information, such as all the sensory information you received, what you were doing, where it occurred, the time of day, and your emotional state. Some of these parts may also be components of other similar memories and form larger memory connections.

In addition, memory for an event or experience can change over time, with details added or lost. This is why it is not good to rely on one person’s memory for eyewitness testimony during court proceedings.

Often we wish we could remember everything that happens to us. Fortunately we can’t, because we would suffer from memory overload. It makes sense not to remember things that are not important. And some very stressful or emotional events can be difficult to forget even when we want to. This can lead to problems such as post-traumatic stress disorder. Similarly, events that are much too rewarding are also hard to forget, and can lead to drug addiction or problem gambling.