Hungry individuals are often bad tempered and aggressive. Now scientists believe that it is not simple belligerence but follows a decline in serotonin, whose manufacture in the body depends on eating well and regularly.

Serotonin is one of the most important chemical messengers. It is made in the body from foods such as chicken soup and chocolate, which are rich in the chemical tryptophan (hence, some think, the "feel-good" factor associated with these foods). Serotonin levels are, inevitably, lower when someone is hungry.

Some kind of association between serotonin and behaviour had been suspected for some time but now Cambridge University scientists have the proof of the pudding, as it were, by persuading volunteers, both hungry and well-fed, to play a game that tests reactions to unfair behaviour. As the players' serotonin levels fell, their ire rose at what they saw as unreasonable actions by their opponents.

Molly Crockett, one of the Cambridge team, said: "Our research suggests serotonin plays a critical role in social decision-making by normally keeping aggressive responses in check."

The result may help to explain illnesses associated with low serotonin levels such as depression and obsessive compulsive disorder. The work is reported in Science Express on the 6 June.

饥饿的人往往脾气暴躁并富于攻击性。目前科学家认为，这不是简单的好斗，而是血清素(serotonin)水平降低造成的。人体内制造血清素凭借的是良好、规律的饮食。

血清素是最重要的传递信息的化学物质之一。在人体内，血清素由鸡汤和巧克力等食物制造，这些食物富含一种化学物质色氨酸(tryptophan)（因此有些人认为，"感觉良好"的因素与这些食物有关）。当人饥饿时，血清素的水平必然会降低。

人们怀疑血清素与行为之间存在某种联系已经有一段时间，不过现在英国剑桥大学(Cambridge Univeristy)的科学家通过实验找到了证据。科学家们说服饥饿的和吃饱的志愿者参加一个游戏，测试他们对不公平行为的反应。随着参加测试者血清素水平的下降，他们对于另一方不合理行为的愤怒水平会上升。

剑桥团队的成员之一莫利•克罗基特(Molly Crockett)表示："我们的研究表明，血清素在社会决策行为中扮演着重要角色，通常它能控制攻击性反应。"

该研究结果也许能有助于解释抑郁症和强迫症(OCD)等与低血清素水平相关的疾病。《科学快讯》(Science Express)于6月6日报道了此项研究。
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