When an actor takes on a character's persona fully for exploration, this is known as:

Role play involves an actor immersing themselves fully into a character’s persona in order to explore their thoughts, feelings, and behaviors. This technique allows the actor to delve deeply into the character's motivations and backstory, which can enrich their performance and understanding of the role. By engaging in role play, actors often find new dimensions to their characters that may not surface through script reading alone.

The other options, while related to acting and character development, serve different purposes. Character cards are tools that help actors outline important traits and objectives of a character, rather than a full immersion into the role. Improvisation allows actors to create spontaneous dialogue and actions, but it does not necessarily mean adopting the persona fully in a planned exploration. Hot seating is a technique where an actor sits in front of others and answers questions as their character, which can also promote deeper understanding but is more about external interaction than internal persona exploration.