There's two types of avatar designs:
- the avatar as empty shell that the player uses to express what they would do in the game
- the avatar as character in the story whose role the player plays
The first is obviously problematic because a game creates a fictional universe that may be improbably to find yourself in. And expects the player to do things which they may never do voluntarily.
But the second is problematic as well. Because the character that you are asked to play has already lived a life. And you, as a player, do not know anything about this life! As a result, the character may display inappropriate symptoms of amnesia. And the player may not understand the environment and the characters they meet as well as they should, if they were the character.
I imagine actors would solve this problem in one of two ways. Either they simply follow directions, say the lines in the script and follow their intuition in terms of tone of voice (or they experiment over multiple takes in the case of a recording, and let the editor decide). Or they really try to get to know the character that they are playing and try to imagine being this person and try to live how this person lives (perhaps not always restricted to the stage or set...).
Players of games can't do either. They can't do the first because they are not just the player, they are also the audience. And as audience, they want to understand the story. And they can't do the latter because, well, they just want to play and not read a story before they start playing or spend weeks of study and experimentation trying to "get into" the character.
As a result, many games contain an element of learning about the world and characters that your avatar knows so well. Even of learning about the very avatar whose role you are playing. As such, in a way, playing a game is as much writing the story, as it is telling or experiencing it. Within a game structure, this doesn't pose a lot of problems because games are often about learning things too, and about discovery. But in a purely narrative interactive experience, the amnesia of the protagonist poses a serious problem.
How do we solve it?