Multi-Tasking

Several tasks can be accomplished simultaneously. Driving a car and talking, listening to music. A commonly described example is a mother holding and feeding a baby while having a conversation with another person entirely. But only one thing can have complete concentration at any one time. Fast switching between tasks can give the impression of multi-tasking with full concentration.

It is possible to walk from one place to another, thinking about something and later reach a point on the journey and not remember anything between the start and where you end up. The brain can easily deal with more than two things at once, but it is not possible to be conscious of all at the same time. Only one of them.

It is possible to play a song (in the mind) though not possible to mentally concentrate on two 'mind songs' at the same time. One at a time only.

The Necker cube illustrates the issue. The 3D cube drawn on a flat surface (2D) can be imagined in two ways. From the top (right-front) looking down or bottom (left-front) and looking up. Switching between the two viewpoints can be mentally very fast, but it is not possible to 'see' both at the same time.

Computers multi-task in a similar way. Running one application alongside another and switching quickly between them as they both run. It appears that they are running independently, though only one is being processed at any one time.

• Systems do exist that have two processors or cores (multi-core processor or parallel computing), yet this is like having two brains.