1. A method for rating media, the method comprising: obtaining a first signal from a brain of an individual produced substantially while the individual is exposed to the media; obtaining a second signal from a heart of the individual produced substantially concurrently with the first signal from the brain; decomposing the first signal and the second signal into a frequency domain; calculating with a processor, an engagement value based on a first mathematical relationship between (1) a first frequency and (2) a second frequency from the frequency domain of the first signal and a second mathematical relationship between (1) a third frequency from the frequency domain of the second signal and (2) a result of the first mathematical relationship; comparing the engagement value with a reference value to determine a difference; and rating the media based on the difference between the engagement value and the reference value.