那些在退休前从事过精神刺激、要求高的工作的人在测试中表现最好。

Those who had held mentally stimulating, demanding jobs before retirement tended to do the best on the tests.

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没有这种精神刺激，人类合作就完全不可能；

With absence of mental stimulus of this kind, human cooperation would be entirely impossible;

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我们最终感受到的疲劳而不是持续的精神刺激。

Eventually, however, rather than continued mental stimulation, we begin to experience fatigue.

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