The word "attention" carries a few meanings that depend on how and when it is used. In the military, a soldier is expected to stand upright and face the incoming officer no matter what he is doing. The soldier would salute to show his respect. No soldier understands the command for "attention" to mean "stay sitting." He acknowledges and shows his understanding by rising quickly.
It doesn't do us any good to just sit up and take notice if we are commanded to stand. There is an action that is required when God calls us. When God speaks, we are to be at attention and we are to act. Living by every word from God includes taking notice of His commands and then acting (James 2:18).