When the simulation is opened a field is shown with some red dots in random distribution. They are sufficiently close to perceive their number at a glance.
The number of points displayed is changed periodically at random between 1 and a maximum number that can be edited in the number field. Default value is a maximum of 5 dots.
A slider defines the changes per second between 1 and 10.
A narrow second window shows how many points are displayed at any moment. This window can be concealed by a check box. It can also be drawn out of the field of view of the experimenting person to allow control by a second person.
Try to perceive with certainty the number of points without counting (scanning).
Up to 5 points this should be no problem. Beyond 7 it will be barely possible. This finding does not vary substantially with moderate changes in the speed of presentation.