In an experiment, the independent variable is the variable that is manipulated by the researcher, and the dependent variable is the response that is measured.
E.g. The Independant variable is whether the tv was on or not and the dependant variable is the pp's score on the memory test.
An experimenter has to control extraneous variables otherwise the results of the study will be meaningless.
Mundane realism = how an experiment mirrors the real world.
Watching a car accident on a film in a laboratory lacks mundane realism because it isn't realistic and so the results of the study may not be very useful in terms of understanding behaviour in the real world.