1. His head moves up and down.
2. His head moves down and up.
[#1 is correct. What about #2? do you use 'down and up'?]
3. His head nods.
4. He nods his head.
[Are both the same as #1?]
2. His head moves down and up.
[#1 is correct. What about #2? do you use 'down and up'?]
3. His head nods.
4. He nods his head.
[Are both the same as #1?]