There is a strong relationship between fluid intelligence and working memory capacity (WMC). Yet, the cognitive mechanisms underlying this relationship remain elusive. The capacity hypothesis states that this relationship is due to limitations in the amount of information that can be stored and held active in working memory. Previous research aimed at testing the capacity hypothesis assumed that it implies stronger relationships of intelligence test performance with WMC for test items with higher capacity demands. The present article addresses this assumption through simulations of three theoretical models implementing the capacity hypothesis while systematically varying different psychometric variables. The results show that almost any relation between the capacity demands of items and their correlation with WMC can be obtained. Therefore, the assumption made by previous studies does not hold: The capacity hypothesis does not imply stronger correlations of WMC and intelligence test items with higher capacity demands. Items varying in capacity demands cannot be used to test the causality of WMC (or any other latent variable) for fluid intelligence.

流体智力与工作记忆容量 (WMC) 之间存在密切关系。然而，这种关系背后的认知机制仍然难以捉摸。容量假说指出这种关系是由于工作记忆中可以存储和保持活跃的信息量的限制。以前的研究旨在检验容量假设，假设它意味着智力测试性能与 WMC 对于具有更高容量需求的测试项目有更强的关系。本文通过模拟实现能力假设的三个理论模型同时系统地改变不同的心理测量变量来解决这一假设。结果表明，几乎可以得到项目容量需求与WMC 相关性之间的任何关系。因此，以往研究所做的假设并不成立：能力假设并不意味着WMC和智力测验项目的相关性更强，能力需求更高。