原文已被隐藏，你可用 快捷键 - 或点击 显示原文 按钮来查看原文
第1段
1 .This is Scientific American 60-Second Science. I'm Sophie Bushwick. Got a minute?
该句暂无译文！
2 .Roosters greet the rising sun with.
该句暂无译文！
3 .But they also crow at other times.
该句暂无译文！
4 .So are they responding to the light?
该句暂无译文！
5 .Or do they simply know that it's morning?
该句暂无译文！
6 .New research says the latter: roosters crow because of internal time cues.
该句暂无译文！
7 .The finding is in the journal Current Biology.
该句暂无译文！
8 .Scientists controlled the light levels in rooster habitats.
该句暂无译文！
9 .For two weeks, the birds experienced 12 hours of light followed by 12 hours of dim light.
该句暂无译文！
10 .Consistent with the pre-dawn noises observed in wild fowl, the roosters began to crow about two hours before their rooms lit up.
该句暂无译文！
11 .Then, for two weeks, the roosters lived in constant dim light.
该句暂无译文！
12 .Yet they continued to crow about once a day--at intervals of 23.7 hours to be precise.
该句暂无译文！
13 .Even without morning light, their circadian rhythms told them when dawn should be breaking.
该句暂无译文！
14 .The birds also crowed in response to sudden light, and to the sounds of other roosters.
该句暂无译文！
15 .But they were more likely to react when those stimuli occurred near dawn.
该句暂无译文！
16 .Showing that you can't really keep a rooster in the dark about the time.
该句暂无译文！
17 .Thanks for the minute, for Scientific American 60-Second Science. I'm Sophie Bushwick.
该句暂无译文！