What could possibly be going through her mind?

Sandy and I were playing stick in the front yard this afternoon, when suddenly she just stopped, and looked like this:

She stood there for over a minute, tail relaxed, ears not twitching, checking out something to which I was completely oblivious.

Then, she just got on with her life.  She picked up the stick, trotted over to another section of the yard, lay down and continued with the important task of peeling all the bark off the stick.

I wonder if Sandy is just as confused by strange things I do, making a double espresso in the morning, or standing over the table and adding things to the grocery list.