While a higher IQ correlates with skills such as numeracy ，which is essential to understanding probabilities and weighing up risks，there are still many elements of rational decision making that can not be accounted for by a lack of intelligence.

这里为什么是essential to doing？为什么在be accounted for后面又加了by？

答：1、这里的to介词，而不是不定式的标志，be essential to doing sth对于做......来说是必不可少的。

 2、account for是对......作出解释，说明......的原因。

many elements of rational decision making在that引导的定语从句中作主语，与a lack of intelligence是被动关系，即：依然有许多理性决策的因素无法通过智力不足来解释（字面意思）。

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