This is a random thought that popped into my brain for some reason this morning and won’t go away. Why are movies able to reuse actors and still work? Once we see someone in a movie as a certain character, if we see them in something else shouldn’t our minds go ‘Hey that’s 'firstcharacter'’ and prevent us from engaging in the new movie? Or possibly, because the actor is now associated with two characters, say ‘Hey that’s 'theactor'’ and prevent us from engaging in either movie now if we go back and rewatch the first one?
How is it that we can realize it’s the same person yet accept that it’s not in the confines of this movie, and have our minds be okay with that and not be distracted?
I think it must have something to do with the new setting and story of the new movie putting a different context around the new character that distracts us from being distracted or something like that. Everything we’re experiencing is saying this is a different person so our minds are just forced to accept it maybe.
Why do movies work?
Movies by nature require a certain suspension of belief. Especially nowadays, half of the stuff you see is being generated by computers - it's the illusion of what's real. We're all trained from a young age on how to suspend our beliefs, and so it's part of our developed minds by the time we're older and we just do it naturally. So the reason you can accept Iron man flying through the air in his suit is the same reason you can watch Robert Downey Jr. play Iron man and not say, "hey I've seen that guy play other roles!" You take notice, of course, which is why we have the Star system to begin with, but you always suspend your beliefs to a certain degree for the sake of the film.
When movies first started showing up in the early 1900's they were more or less documentary shorts, photographing what was real. Then some early innovators decided to take the methods of theater and apply them to film. Film was essentially like theater, and eventually it began to evolve into an art format all its own. But the audience's approach is essentially rooted in theater, which has been around since ancient times.
That being said, some actors can get pigeonholed into a certain role... think of Johnny Depp or Christian Bale. Or Kirk Cameron.
When movies first started showing up in the early 1900's they were more or less documentary shorts, photographing what was real. Then some early innovators decided to take the methods of theater and apply them to film. Film was essentially like theater, and eventually it began to evolve into an art format all its own. But the audience's approach is essentially rooted in theater, which has been around since ancient times.
That being said, some actors can get pigeonholed into a certain role... think of Johnny Depp or Christian Bale. Or Kirk Cameron.
Fallacy of false continuum. // bookworm
Any cupcake can be made holy through being baptized in the name of the Butter, the Vanilla and the Powdered Sugar. // Kait
Any cupcake can be made holy through being baptized in the name of the Butter, the Vanilla and the Powdered Sugar. // Kait
This is a very interesting question. As a short answer, for myself personally, movies can reuse actors because I don't recognize or know most of them anyway. 
As a more thoughtful answer, I would say seeing a very familiar actor in a different movie could be problematic for others. If someone is conditioned towards seeing them in a certain role, a movie that breaks away from that model could be confusing to the mind, especially if the personality of the actor's character differs. Or, it could work the other way. If a familiar actor is in a very similar movie to the productions they have been a part of in the past, it may be confusing to constantly see them in similar situations or perspectives that were highlighted in the previous movie.
This section of my answer will assume that I do indeed recognize actors in movies, so it may not be entirely accurate. Personally, if I compare reading a book to watching a movie, there is usually a short period in which I have to become accustomed to the setting and perspective of the book. This usually takes a few pages or minutes, and it usually takes me about this period of getting the setting and perspective transferred into my mental interpretation of the book. By this point, I typically have become completely engrossed in the book, and will either continue to a convenient stopping place (either the end of the book or the point where I stop understanding what I am reading) or I have to enticed away from it.
If I translate this to movie-watching, I would say that if a very familiar actor was playing a character in a movie, it would take me a small adjustment period in which to develop a mental perspective of the movie. I would begin to associate the actor's face and personality with the setting and theme of the movie. For example, if I have just finished watching the Star Wars trilogy, and then switch immediately to watching Indiana Jones, it would probably take me a small period of time to become adjusted to seeing Harrison Ford in a completely different setting and perspective. Because the overall personality of the characters he plays is somewhat similar, this process might not take very long.
As a more thoughtful answer, I would say seeing a very familiar actor in a different movie could be problematic for others. If someone is conditioned towards seeing them in a certain role, a movie that breaks away from that model could be confusing to the mind, especially if the personality of the actor's character differs. Or, it could work the other way. If a familiar actor is in a very similar movie to the productions they have been a part of in the past, it may be confusing to constantly see them in similar situations or perspectives that were highlighted in the previous movie.
This section of my answer will assume that I do indeed recognize actors in movies, so it may not be entirely accurate. Personally, if I compare reading a book to watching a movie, there is usually a short period in which I have to become accustomed to the setting and perspective of the book. This usually takes a few pages or minutes, and it usually takes me about this period of getting the setting and perspective transferred into my mental interpretation of the book. By this point, I typically have become completely engrossed in the book, and will either continue to a convenient stopping place (either the end of the book or the point where I stop understanding what I am reading) or I have to enticed away from it.
If I translate this to movie-watching, I would say that if a very familiar actor was playing a character in a movie, it would take me a small adjustment period in which to develop a mental perspective of the movie. I would begin to associate the actor's face and personality with the setting and theme of the movie. For example, if I have just finished watching the Star Wars trilogy, and then switch immediately to watching Indiana Jones, it would probably take me a small period of time to become adjusted to seeing Harrison Ford in a completely different setting and perspective. Because the overall personality of the characters he plays is somewhat similar, this process might not take very long.
"And the fire with all the strength it hath."