The computer draws some circles. The user must define the number of the circles
in no time (in one moment).
There is a theory that the human mind can keep 5- 9 objects at one time.
However you can learn to keep and analyze more than 9 objects in mind. It is
possible if you unit some objects in one group.
You must not try to count circles, but divide them in a group of 3-5 circles.
Then appreciate the sum intuitively.