介绍： This is Scientific American 60-second Science, I'm Lucy Huang.
Mice and rats vocalize.
To us, many of the sounds they make are ultrasonic―at too high a frequency to hear.
But if we slow the calls down, they sound like squeaks.
And not all squeaks are the same.
The sounds that rodents make when they are excit...

介绍： This is Scientific American 60-second Science, I'm Lucy Huang.
Mice and rats vocalize.
To us, many of the sounds they make are ultrasonic―at too high a frequency to hear.
But if we slow the calls down, they sound like squeaks.
And not all squeaks are the same.
The sounds that rodents make when they are excited versus disappointed can be quite different.
For example, here's slowed-down audio of a rat drinking sugar water.
But this rat got played―it got non-sweetened water after becoming accustomed to sugar water.
"Calls around 22 kilohertz are usually associated with unhappy affect and calls around 55 kilohertz are happy affect."
John Neumaier, a professor of psychiatry and pharmacology at the University of Washington.
"So if you tickle a rat, it puts out a lot of 55 calls.
If we give them a sucrose solution, then they put out a lot of calls at 55 kilohertz."

这里是科学美国人――60秒科学系列，我是露西・黄。
小老鼠和大老鼠都会发声。
对我们来说，它们发出的许多声音都是超声波――因频率过高而听不见。
但如果我们将它们的叫声放慢，听起来就像是吱吱声。
并不是所有的吱吱声都是一样的。
老鼠在兴奋和失望时发出的声音可能截然不同。
例如，这是大老鼠喝糖水时所发出声音的慢放音频。
但这只大老鼠被耍了――在它习惯了糖水之后，研究人员给了它无糖水。
“约22千赫的叫声通常与不快乐的情绪有关，而约55千赫的叫声表明的是快乐情绪。”
华盛顿大学心理学和药物学教授约翰・纽迈尔说到。
“因此，如果让大老鼠开心，它会发出很多55千赫的叫声。
如果我们给它们蔗糖溶液，它们就会发出大量55千赫的叫声。”