Perception Cardinality While reading a science fiction book, Calculating God by Robert J. Sawyer, I came across the following lines:

“Well, if I showed you one object - one rock, say - you would not have to count it. You would just perceive its cardinality: you would know there was one object. The same thing happens with two objects. You just look at the pair of rocks and in a single glance, without any processing, you perceive that there are two of them present. You can do the same with three, four, or five items, if you are an average human. It is only when confronted with six or more items that you actually start counting them.”

“How do you know this?”

“I watched a program about it on the Discovery Channel.”

Assuming this is a real psychological phenomenon, is there a name or reference for it? I have contacted the author but have not received a response yet.
The author responded. It is called "Subitising" or "Subitizing" or "Perceiving cardinality at-a-glance". The term was coined by Kaufman in 1949.