My research has found that any new smell, even one associated with relaxation, like lavender, can make you more alert and vigilant.

我的研究表明：在闻到的任何以前从未闻过的气味的时候，哪怕是像薰衣草那样能让你感到放松的气味，人都会警惕起来。

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Contagious yawning is thought to be an evolved mechanism for keeping groups alert so they "remain vigilant against danger," Gallup said.

呵欠传染被认为是进化出来用于保持群体的警惕性使群体“在危险面前保持警觉，”盖洛普说。

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The alert is expected to urge American citizens in Europe to be vigilant, especially when in public places such as public transportation, airports, and tourist sites, officials said.

该警告旨在使欧洲的美籍人员保持警惕，尤其是在公共场合，如公交车站，机场和旅游景点。

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