Within- and between-trial measures: Revealing hidden effects

In many experiments usually one measure is taken at a particular moment in time:  For example, a reaction time to identify a stimulus.  From such a measure we observe patterns in the data and build theories of cognitive processes.   However, it can be the case that employing only one measure can have serious limitations.  Hence, it can be preferable to examine processing at different times or use a different measure.  Such converging approaches can reveal previously unobservable effects that can have important implications for the theories we develop.