From a writing standpoint, this is a great way of following the mantra of Showing versus Telling.
Behavior is observable and describable, and better yet, communicates more actively than simply telling what a character is doing or thinking, especially in those ever popular but problematic ‘ly’ dialog tags.
“Give it to me!” Character said angrily.
“Give it to me!” Character said, eyes narrowing.
When writing, think about behavioral clues to that show what is going on rather than relying on weaker forms of description.