恐惧是一种习得反应。

Fear is learned and must be unlearned .

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其他研究人员抗议说，“选择退出”反应只是一种习得的或条件性的反应。

Other researchers protested that the opt-out response was simply a learned or conditioned response.

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但想要分清这些反应是先天本能，还是后天习得可不是那么容易。

But it is difficult to say if these reactions are instinctive or learnt.

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