When a measure becomes a target, it often ceases to be a good measure - an effect familiar from the declining usefulness of standardized testing in schools. This economic principle also applies to mate choice and, perhaps surprisingly, pregnancy. Just as females screen potential mates under many metrics, human mothers unconsciously screen embryos for quality. 'Examinees' are under intense selection to improve test performance by exaggerating formerly 'honest' signals of quality. Examiners must change their screening criteria to maintain useful information (but cannot abandon old criteria unilaterally). By the resulting 'proxy treadmill', new honest indicators arise while old degraded indicators linger, resulting in trait elaboration and exaggeration. Hormone signals during pregnancy show extreme evolutionary escalation (akin to elaborate mating displays).

中文翻译：

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胚胎选择和伴侣选择：“诚实信号”可以信赖吗？

当一项措施成为目标时，它通常就不再是一项好措施-学校标准化测试的实用性下降而产生的效果。这种经济原则也适用于配偶的选择，也可能适用于怀孕。就像雌性在许多条件下筛选潜在配偶一样，人类母亲在不知不觉中对胚胎进行质量筛选。为了增强测试性能，“检查员”正在严格选择，以夸大以前“诚实”的质量信号。审查员必须更改其筛查标准，以保持有用的信息（但不能单方面放弃旧标准）。通过产生的“代理跑步机”，新的诚实指标出现，而旧的退化指标徘徊不前，从而导致性状细化和夸张。