1. Alcohol causes a loss of judgment and alertness. 酒精会使人丧失判断力和警觉性。
2. The drug improved mental alertness. 这种药物提高了大脑的灵敏度。
3. Decades of studies of bird flocks led researchers to predict extra alertness in the more vulnerable, end of the row sleepers. 通过对鸟群几十年的研究，研究人员预测，那些更容易受伤的、睡眠时处于队列末端的鸟会格外警觉。
4. Another flaw of the tiredness theory is that yawning does not raise alertness or physiological activity, as the theory would predict. 疲劳理论的另一个缺陷是，打哈欠并不能像该理论所预测的那样，提高警觉性或生理活跃度。
