Sikström S
Department of Psychology, Stockholm University, Sweden.
Psychon Bull Rev. 2001 Sep;8(3):408-38. doi: 10.3758/bf03196178.
The mirror effect refers to a rather general empirical finding showing that, for two classes of stimuli, the class with the higher hit rates also has a lower false alarm rate. In this article, a parsimonious theory is proposed to account for the mirror effect regarding, specifically, high- and low-frequency items and the associated receiver-operating curves. The theory is implemented in a recurrent network in which one layer represents items and the other represents contexts. It is shown that the frequency mirror effect is found in this simple network if the decision is based on counting the number of active nodes in such a way that performance is optimal or near optimal. The optimal performance requires that the number of active nodes is low, only nodes active in the encoded representation are counted, the activation threshold is set between the old and the new distributions, and normalization is based on the variance of the input. Owing to the interference caused by encoding the to-be-recognized item in several preexperimental contexts, the variance of the input to the context layer is greater for high- than for low-frequency items, which yields lower hit rates and higher false alarm rates for high- than for low-frequency items. Although initially the theory was proposed to account for the mirror effect with respect to word frequency, subsequent simulations have shown that the theory also accounts for strength-based mirror effects within a list and between lists. In this case, consistent with experimental data, the variance theory suggests that focusing attention to the more difficult class within a list affects the hit rate, but not the false alarm rate and not the standard deviations of the underlying density, leading to no mirror effect.
镜像效应指的是一个相当普遍的实证发现，即对于两类刺激而言，命中率较高的类别其误报率也较低。在本文中，我们提出了一个简洁的理论来解释关于高频和低频项目以及相关的接收者操作曲线的镜像效应。该理论在一个循环网络中得以实现，其中一层表示项目，另一层表示上下文。结果表明，如果决策基于以一种使性能达到最优或接近最优的方式对活跃节点进行计数，那么在这个简单网络中就能发现频率镜像效应。最优性能要求活跃节点数量较少，只对编码表示中活跃的节点进行计数，激活阈值设置在旧分布和新分布之间，并且归一化基于输入的方差。由于在几个实验前的上下文中对要识别的项目进行编码所产生的干扰，上下文层输入的方差对于高频项目而言大于低频项目，这导致高频项目的命中率低于低频项目，误报率高于低频项目。尽管最初提出该理论是为了解释关于词频的镜像效应，但后续模拟表明该理论也能解释列表内和列表间基于强度的镜像效应。在这种情况下，与实验数据一致，方差理论表明在列表内关注更难的类别会影响命中率，但不会影响误报率以及基础密度的标准差，从而不会产生镜像效应。
