Di Nocera F, Ferlazzo F
Department of Psychology, University of Rome La Sapienza, Italy.
Behav Res Methods Instrum Comput. 2000 Feb;32(1):111-9. doi: 10.3758/bf03200793.
We propose the use of the bootstrap resampling technique as a tool to assess the within-subject reliability of experimental modulation effects on event-related potentials (ERPs). The assessment of the within-subject reliability is relevant in all those cases when the subject score is obtained by some estimation procedure, such as averaging. In these cases, possible deviations from the assumptions on which the estimation procedure relies may lead to severely biased results and, consequently, to incorrect functional inferences. In this study, we applied bootstrap analysis to data from an experiment aimed at investigating the relationship between ERPs and memory processes. ERPs were recorded from two groups of subjects engaged in a recognition memory task. During the study phase, subjects in Group A were required to make an orthographic judgment on 160 visually presented words, whereas subjects in Group B were only required to pay attention to the words. During the test phase all subjects were presented with the 160 previously studied words along with 160 new words and were required to decide whether the current word was "old" or "new." To assess the effect of word imagery value, half of the words had a high imagery value and half a low imagery value. Analyses of variance performed on ERPs showed that an imagery-induced modulation of the old/new effect was evident only for subjects who were not engaged in the orthographic task during the study phase. This result supports the hypothesis that this modulation is due to some aspect of the recognition memory process and not to the stimulus encoding operations that occur during the recognition memory task. However, bootstrap analysis on the same data showed that the old/new effect on ERPs was not reliable for all the subjects. This result suggests that only a cautious inference can be made from these data.
我们建议使用自助重采样技术作为一种工具，来评估事件相关电位（ERP）实验调制效应的受试者内信度。当通过某种估计程序（如平均）获得受试者分数时，受试者内信度的评估在所有这些情况下都是相关的。在这些情况下，与估计程序所依赖的假设的可能偏差可能导致严重有偏差的结果，并因此导致不正确的功能推断。在本研究中，我们将自助分析应用于一项旨在研究ERP与记忆过程之间关系的实验数据。ERP是从两组参与识别记忆任务的受试者中记录的。在学习阶段，A组受试者被要求对160个视觉呈现的单词进行正字法判断，而B组受试者只被要求注意这些单词。在测试阶段，所有受试者都看到了160个之前学习过的单词以及160个新单词，并被要求判断当前单词是“旧的”还是“新的”。为了评估单词意象值的影响，一半的单词具有高意象值，一半具有低意象值。对ERP进行的方差分析表明，意象诱导的旧/新效应调制仅在学习阶段未参与正字法任务的受试者中明显。这一结果支持了这样的假设，即这种调制是由于识别记忆过程的某些方面，而不是由于识别记忆任务期间发生的刺激编码操作。然而，对相同数据的自助分析表明，ERP上的旧/新效应并非对所有受试者都可靠。这一结果表明，从这些数据中只能进行谨慎的推断。
