Picking up each crayon and putting it back is learning. You can say "one, two, three..." to set up the audio pattern for counting in the future. Begin with three crayons. The high chair is a perfect setting for scribbling... good seating and a contained work surface. A safe place to practice her skills while dinner is cooking.
PRACTICE: dump/count/dump/count... (click on pic)
At first, just seeing that a line tracks her hand movement is fascinating. Holding a crayon or piece of chalk while pushing down to draw a line is a skill worth practicing.
A few months later... there are intentional lines to be made. Up and down, circle and side to side are lines you can encourage by saying "let's go round and round..." She can be a bit more intentional. You verbalize the concept of "round and round" or "up and down" for her.
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This simple activity demonstrates to your beginner that she is in control and that she can do what she wishes.
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A black board is just wonderful for drawing... lines are bold, there is just enough resistance so that it is easy for your beginner to control her drawing.
We are using sidewalk chalk which is just the right thickness. Also, she can erase with a small piece of sponge and get more motor practice. This black board was mine as a child, it's heavy slate and stays put. It used to be part of an easel that is long gone, another example of the art of saving stuff you might need in the future!
These actions are the equivalent of practicing a back hand in tennis. Your beginner learns how it feels to make round, up and down and side to side movements... she is developing motor memory.
Soon, when she learns to draw shapes, she will know just how to move. Round and round for circles, up and down/side for rectangles.