Losing just two hours of sleep a night makes people angrier, research reveals.

研究显示，每晚少睡两个小时会让人更易怒。

The study is among the first to prove a direct link with lack of shuteye, experts say.

专家称，这是首个证明生气和睡眠不足有直接联系的研究。

Previous research shows sleep loss increases negative emotions, such as anxiety and sadness, and decreases positive emotions, including happiness and enthusiasm.

之前的研究表明，睡眠不足会增加消极情绪，如焦虑和悲伤，减少积极情绪，包括幸福和热情。

But researchers at Iowa State University found losing sleep raised anger directly -- not just as a result of feeling more negative. Their findings were published in the Journal of Experimental Psychology.

但爱荷华州立大学的研究人员发现，睡眠不足会直接引发愤怒，而不仅仅是感觉更消极。他们的研究结果发表在《实验心理学杂志》上。

Participants were split into two groups. One kept to their normal sleep routine while the other had theirs cut by two to four hours each night for two nights.

参与实验者被分成两组。一组保持正常的睡眠习惯，另一组连续两晚每晚减少两到四个小时的睡眠时间。

The first group had almost seven hours of sleep a night, while the restricted group got about four and a half hours.

第一组每晚差不多睡7个小时，而限制睡眠组每晚睡大约4个半小时。

The difference was designed to reflect what people regularly experience in everyday life.

设计这种差异是为了反映人们在日常生活中经常经历的情况。

Both groups were then asked to rate different products while listening to irritating noise. There searchers said this was meant to create uncomfortable conditions and provoke feelings of anger.

两组参与者被要求在听恼人的噪音的同时给不同产品评分。研究人员称，这样做是为了营造不舒服的环境，激起愤怒的情绪。

Study leader professor Zlatan Krizan said: "In general, anger was substantially higher for those who were sleep restricted."

研究负责人兹拉坦·克里萨教授表示：“总的来说，那些睡眠不足的人的愤怒情绪要高得多。”

"We manipulated how annoying the noise was during the task and, as expected, people reported more anger when the noise was more unpleasant. When sleep was restricted, people reported even more anger, regardless of the noise."

“我们对实验过程中噪音的干扰程度进行了调控，结果不出所料，当噪音更恼人时，人们会表现得更愤怒。当睡眠不足时，不管是否有噪音，人们会表现得更愤怒。”