{zx1}研究：咖啡提神实为心理作用

    很多人称清晨喝杯咖啡后，才能神清气爽地开始工作。但最近研究人员发现，咖啡中的xxx带来的“兴奋效应”很可能只是人们的心理作用而已。

    布里斯托尔大学最近的研究中，379名志愿者被要求在16个小时之内不得服用任何xxx饮料，16个小时之后一组开始饮用xxx饮料，另一组以为自己饮用的也是xxx饮料，而实际上没有。结果显示，两组志愿者的警觉兴奋程度并没有多大区别。

   “我们的研究表明，饮用xxx并没有让我们从中得到什么好处，”该研究首席顾问、布里斯托尔大学实验心理学专业教授彼得罗杰斯说道。

    但是为什么人们在清晨一杯咖啡后感觉确实不太一样？研究人员称，原因很可能是这杯咖啡扭转了一夜没有xxx供给所带来的“疲惫效应”。

    此项研究中，大约一半的志愿者不喝或者饮用很少量的xxx饮料，而另一半志愿者过去饮用此饮料较多。研究要求所有人进行计算机测试以检测他们的记忆力、注意力以及灵敏度。结果曾饮用较多的志愿者在饮用了假xxx饮料后，警觉度下降、更多人xx，以前很少饮用xxx饮料的志愿者则没有出现这些现象。

    在补充了xxx之后，出现不适症状的人群得以恢复，但灵敏度并没有比其他人高多少。故而该研究证明了“xxx只能将人体机能带回到正常状态而已”。

    据研究人员称，此项发现不仅适用于爱喝咖啡者，同样适用于清晨一杯茶才能使其投入工作的人群。

   Many say their brains don't start working properly in the morning until they have had a cup of coffee. But the stimulating effect for which caffeine is famous for may be an illusion, say researchers.

   In a study carried out by Bristol University recently, 379 people who abstained from caffeine for 16 hours before drinking either caffeine or a placebo (dummy drink) were tested for a range of responses afterwards. The researchers found little variance in levels of alertness among the volunteers.

   Peter Rogers, from the university's department of experimental psychology and one of the leading authors of the study, said: "Our study shows that we don't gain advantage from consuming caffeine."

   But what makes people feel different after a cup of coffee in the morning? The researchers say that it is because it reverses the fatiguing effects of overnight caffeine withdrawal.

   Around half the volunteers drank little or no caffeine and the other half were medium-high caffeine consumers. All were asked to carry out a series of computer tasks to test their level of memory, attentiveness and vigilance. The medium-high caffeine consumers who received the dummy drink reported a fall in alertness and an increase in headaches, neither of which were reported by those who received caffeine.

   However, their post-caffeine levels of alertness were no higher than those of no or low-level consumers who received a placebo. This suggests caffeine only brings coffee drinkers back up to "normal".

   The researchers said their findings could also apply to those who claim they rely on a morning cup of tea to get their brains going.