Alpha waves are prominent when people are relaxed; on the other end of the spectrum, beta waves emerge in states of concentration or deep thought. The remaining theta and delta waves are most conspicuous when people are in the initial stages of sleep and deep slumber respectively.
其中，人若在平靜、放鬆狀態時，通常 α 波會較高；反之若處於緊張、思考、專注時，β 波則會升高；θ 波和 δ 波則分別在剛入眠及沈睡時出現。