Previous studies have shown that, in samples of non-Western observers, susceptibility to the Ebbinghaus illusion is stronger in urban than rural dwellers. While such relationship between illusion strength and urbanicity has often been ascribed to external factors (such as the visual impact of the environment), the present study explored the possibility that it is instead mediated by general cognitive ability, an internal factor. We recruited a sample of remote Namibians who varied in their level of urbanicity, and measured their susceptibility to the Ebbinghaus illusion, their levels of education and literacy, and their general cognitive ability. The results showed that urbanicity was related to Ebbinghaus susceptibility, and that general cognitive ability, literacy and education did not mediate this effect, which is reassuring with regard to the findings of previous studies that did not control for these variables. However, we found robust relationships between urbanicity, on the one hand, and cognitive ability, education and literacy, on the other, which advocates for careful consideration of the impact of the latter variables in studies about the cognitive effects of urban environments.

先前的研究表明，在非西方观察者的样本中，城市居民对艾宾浩斯错觉的敏感性比农村居民更强。虽然幻觉强度和城市化之间的这种关系通常被归因于外部因素（例如环境的视觉影响），但本研究探讨了这种关系是否由一般认知能力（一种内部因素）介导的可能性。我们招募了一些城市化水平各异的偏远纳米比亚人样本，并测量了他们对艾宾浩斯错觉的敏感性、他们的教育和识字水平以及他们的一般认知能力。结果表明，城市化与艾宾浩斯易感性相关，而一般认知能力、读写能力和教育程度并没有调节这种影响，这相对于之前没有控制这些变量的研究结果来说是令人放心的。然而，我们发现，一方面，城市性与认知能力、教育和识字率之间存在着密切的关系，这主张在关于城市环境认知影响的研究中仔细考虑后者变量的影响。