>>89305084well a lot of the examples in this are for different resaons
head moves with dialog have a few reasons for happening
1. moving hold
the character isn't moving but if you don't draw small subtle movements the character appears to go stiff or "die"
2. pose change
the characters pose is actually changing to emphasis dialog, just like any other pose in animation to express emotions and communicate the story.
3. rotating the head to keep the model looking 3d. (don't know if this has a specific name) when you move a models head left and right you have to move it up and down slightly to keep it 3d or it looks very very flat and wrong.
