核心问题
He( = A psychologist) would point out that observation or perception is a concept which refers not so much to acuteness of sight, hearing, etc., or to the care with which they are applied, as to the ability to relate phenomena to a complex network of previous experiences and theories, i.e. to a meaningful frame of reference. (A Course in Basic Scientific English, p.77)
[原译]他会指出观察或感觉是一个概念。这概念指的与其说是视觉、听觉等等的敏锐性或使用这些知觉的敏锐性的谨慎小心，倒不如说是把这些现象同先前的经历与理论的复杂网络联系起来的能力，也就是说同一个有意义的参照系联系起来的能力。（中译本）
原译文把 they 理解为指“敏锐性”，这似乎讲不通。请您帮助分析一下。
词典解答
从语法上看,they 不可能替代 acuteness(因为 acuteness 是单数名词),而只能替代 sight, hearing, etc.。
[试译]他们会指出,观察或感觉是这样一种概念:这种概念所指的与其说是看、听等的敏锐性,或者看、听等的仔细程度,还不如说是把现象同先前的经历和理论的复杂网络即有意义的参照系联系起来的能力。