Subitising is the instant recognition of patterns of shapes to be able to determine a number. There are many different ways in which we all see these patterns and they are a lively discussion topic for any primary grade class to determine how we interpret these displays of dots.
I encourage you to view this dot number talk by Jo Boaler in one of her many inspirational presentations https://vimeo.com/129139086 where she works through this concept with a middle primary group of students.
As the slides increase in difficulty the students transfer their knowledge from class discussions and can readily determine a quite complex display of dots on a page.
The graphics are engaging and visually inviting for students with some wonderful clipart from Manny's Sketchpad .
A useful addition to any Maths Teaching resource kit for primary school teaching.