Frequency following response (a prime factor in brainwave entertainment), is an observable event which shows an external stimulus being mirrored by internal processes within the brain. This effect can be excited by sound, vision, or any other sense which the brain takes as input.
Melodic or rhythmical waveforms, such as: ocean waves, thunderstorms, and grand symphonies; have all moved the human brain into broader, more advanced ways of utilizing the relationship between mind and brain.
Lit candles or soft music help us to relax and calm an overactive mind. For thousands of years humankind has known that flickering light, melody and rhythm effected body, mind and spirit.
Interestingly, there is a viable theory that the evolution of the Homo Sapien brain may be attributed to our first uses of fire.
The idea is that the dietary improvements of cooking with fire allowed more physical development to take place within the brain. In conjunction with this benefit, it is hypothesized that the flickering, cascading rhythms of the flame's dance led to new neural pathway development and new ways of thinking.
The larger, more intricately structured brains provided an upgrade into advanced thought forms. These crystallizing patterns of thought and action ultimately opened towards ideas of advanced language, community, art, science, engineering, and (of course) music...
Indeed, the "shapes" and "forms" of our experience earn their namesake as they shape and form the evolution of the mind itself. To add proof to beauty, science confirms that the brain 'follows' the rhythms and excitations of our very creation.
In the 1940's, neurophysiologist William Gray Walter, proved that the brain's EEG activity (primarily alpha and beta waves) will follow flickering light (such as a candle of fire). This effect has since been regarded as the brain's frequency following response (FFR).
Today, scientific experimentation has rendered it known that repetitive light and sound frequencies will directly stimulate brain wave activity. Various psychologist and researchers apply this knowledge towards brain wave synchronization therapies. A noticeable use of this technology is the ability to self-direct deep levels of relaxation and focused states of hypnosis, as well as, "altered states of awareness". Research and application also point toward therapies for ADD/ADHD, stress, sleep disorders, neural-pathway stimulation and more.