University of Copenhagen, Copenhagen, Denmark.
Psychon Bull Rev. 2009 Dec;16(6):1000-10. doi: 10.3758/PBR.16.6.1000.
The change detection paradigm is a popular way of measuring visual short-term memory capacity. Using the paradigm, researchers have found evidence for a capacity of about four independent visual objects, confirming classic estimates that were based on the number of items that could be reported. Here, we determine the reliability of capacity measures found by change detection. We derive theoretical predictions of the variance of the capacity estimates and show how they depend on the number of items to be remembered and the guessing strategy of the observer. We compare the theoretically derived variance to the variance estimated over repeated blocks of trials with the same observer and find close correspondence between predicted and observed variances. Also, we propose a new version of the two-alternative choice change detection paradigm, in which the choice is unforced. This new paradigm reduces the variance of the capacity estimate substantially.
变化检测范式是一种测量视觉短期记忆容量的常用方法。研究人员使用该范式发现了大约四个独立视觉对象的容量证据，证实了基于可报告项目数量的经典估计。在这里，我们确定了变化检测中发现的容量测量的可靠性。我们推导出了容量估计方差的理论预测，并展示了它们如何依赖于要记住的项目数量和观察者的猜测策略。我们将理论推导的方差与同一观察者的重复试验块中估计的方差进行比较，发现预测和观察到的方差之间存在密切对应关系。此外，我们提出了一种新的二择一选择变化检测范式，其中选择是不受强制的。这种新的范式大大降低了容量估计的方差。
