The easiest form of slave revolt was the most common. They left their homes for Yankee lines.
They did that in droves, enough to provide numerous regiments of soldiers to the US Army.
I figure they were bright enough to revolt against slavery in the way that gave them the best chance of success.
That makes them smarter than the average Confederate.
Runaway slaves in CSA territory were rare during the war unless the union line was right upon them.