Neural Correlates of the In-Group Memory Advantage on the Encoding and Recognition of Faces

People have a memory advantage for faces that belong to the same group, for example, that attend the same university or have the same personality type. Faces from such in-group members are assumed to receive more attention during memory encoding and are therefore recognized more accurately. Here we use event-related potentials related to memory encoding and retrieval to investigate the neural correlates of the in-group memory advantage. Using the minimal group procedure, subjects were classified based on a bogus personality test as belonging to one of two personality types. While the electroencephalogram was recorded, subjects studied and recognized faces supposedly belonging to the subject’s own and the other personality type. Subjects recognized in-group faces more accurately than out-group faces but the effect size was small. Using the individual behavioral in-group memory advantage in multivariate analyses of covariance, we determined neural correlates of the in-group advantage. During memory encoding (300 to 1000 ms after stimulus onset), subjects with a high in-group memory advantage elicited more positive amplitudes for subsequently remembered in-group than out-group faces, showing that in-group faces received more attention and elicited more neural activity during initial encoding. Early during memory retrieval (300 to 500 ms), frontal brain areas were more activated for remembered in-group faces indicating an early detection of group membership. Surprisingly, the parietal old/new effect (600 to 900 ms) thought to indicate recollection processes differed between in-group and out-group faces independent from the behavioral in-group memory advantage. This finding suggests that group membership affects memory retrieval independent of memory performance. Comparisons with a previous study on the other-race effect, another memory phenomenon influenced by social classification of faces, suggested that the in-group memory advantage is dominated by top-down processing whereas the other-race effect is also influenced by extensive perceptual experience.个体对同群体面孔存在记忆优势——例如同校校友或具有相同人格类型者的面孔。学界普遍认为，此类内群体（in-group）成员的面孔在记忆编码阶段会获得更多注意资源，因此识别准确率更高。本研究采用与记忆编码、提取相关的事件相关电位（event-related potentials, ERP），探究内群体记忆优势的神经关联。本研究采用最小群体范式（minimal group procedure），通过虚假人格测验将被试划分为两种人格类型之一。在记录脑电图（electroencephalogram, EEG）的过程中，被试需要学习并识别两类面孔：一类据称属于自身所属的人格类型，另一类则属于外群体（out-group）人格类型。被试对内群体面孔的识别准确率显著高于外群体面孔，但效应量较小。本研究结合个体行为层面的内群体记忆优势数据开展多变量协方差分析，以此明确内群体记忆优势的神经关联。在记忆编码阶段（刺激呈现后300~1000ms），内群体记忆优势较强的被试，其后续成功记住的内群体面孔相较于外群体面孔，诱发了更正性的脑电振幅，这表明内群体面孔在初始编码阶段获得了更多注意资源，且引发了更强的神经活动。在记忆提取的早期阶段（300~500ms），被试对成功记住的内群体面孔，其额叶脑区激活程度更高，这提示大脑会较早完成群体归属的识别。令人意外的是，被认为反映回想过程的顶叶新旧效应（parietal old/new effect，600~900ms），在内群体与外群体面孔间存在显著差异，且这一差异独立于行为层面的内群体记忆优势。该结果表明，群体归属会独立于记忆表现影响记忆提取过程。通过与此前一项针对异族效应（other-race effect）的研究对比（异族效应是另一类受面孔社会分类影响的记忆现象），本研究发现内群体记忆优势主要由自上而下加工主导，而异族效应则同时受大量知觉经验的影响。