Excerpt: Note that the story also assumes some background knowledge of counting and subitizing; when the snake came upon the second group of mice, how did he know there were four of them without counting one, two, three, four before counting four, five, six, seven? It seems he was able to look at the group of mice and see (or subitize) four.
If the snake knows how to count on, he may not have to know how to subitize, i.e. know there were 4 mice in the second group.
