From “Research puts actors’ memory on center stage“:
According to the researchers, the secret of actors’ memories is, well, acting. An actor acquires lines readily by focusing not on the words of the script, but on those words’ meaning – the moment-to-moment motivations of the character saying them – as well as on the physical and emotional dimensions of their performance.
To get inside the character, an actor will break a script down into a series of logically connected “beats” or intentions. Good actors don’t think about their lines, but feel their character’s intention in reaction to what the other actors do, causing their lines to come spontaneously and naturally. The researchers quote the great British actor Michael Caine: “You must be able to stand there not thinking of that line. You take it off the other actor’s face.”
The key, the researchers have found, is a process called active experiencing, which they say uses “all physical, mental, and emotional channels to communicate the meaning of material to another person.” It is a principle that can be applied off-stage as well as on. For example, students who studied material by imagining conveying its meaning to somebody else who needed the information showed higher retention than those who tried to memorize the material by rote.