Play appears to be a developmental characteristic of animals with fairly sophisticated nervous systems, mainly birds and mammals.

玩耍似乎是具有相当复杂的神经系统的动物（主要是鸟类和哺乳动物）的一种发育特征。

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Herring suggested that different modes of sensation, such as pain, taste, and color, might be correlated with the discharge of specific kinds of nervous energy.

赫灵指出，不同的感觉模式，如痛觉、味觉和色觉，可能与特定种类的神经能量的释放有关。

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I'm a little nervous about that to be honest with you.

说老实话，我对那有点紧张。

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"He will also have to reassure the Poles and the Czechs who I think are feeling a little nervous as to whether they are deemed bargaining chips and might be traded away in some efforts with the Russians.

VOA: standard.2009.07.15

Should Pandora investors really be nervous that Apple might come out with a similar service at some point in the coming months?

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"Parents of young children do often send messages about, 'We can all be friends ... with everybody, ' ... but by adolescence, they start getting more nervous about this and they start thinking, 'Well you should be friends with people like you or like us, ' " said Killen.

CNN: STORY HIGHLIGHTS

Republicans, with a nervous eye on the polls, may be more anxious for a deal than they let on.

ECONOMIST: Barack Obama��s deficit plan