刻板印象激活的无意图性及其大脑神经活动特征

The Pattern and Neural Correlates of Unintentional Stereotype Activation

采用启动Stroop范式,对刻板印象激活的无意图性及其大脑神经活动特征进行了探讨。操纵了启动和"无启动"条件以及与启动所激活的刻板印象一致、冲突和无关的3类靶子词,记录了36名大学生被试对靶子词进行颜色判别的行为反应和脑电图(EEG,electroencephalogram)。结果发现:(1)"无启动"条件下对3类靶子的反应时基本一致;启动条件下对一致靶子做出颜色判别的反应时显著快于对冲突靶子的,对无关靶子的反应时介于两者之间。(2)"无启动"条件下无关靶子诱发的N400波幅最大——显著大于一致和冲突靶子诱发的,后两者诱发的N400无差异;启动条件下一致靶子诱发的N400波幅显著小于冲突和无关靶子诱发的N400波幅,无关靶子诱发的N400波幅也小于冲突靶子诱发的N400波幅。这表明刻板印象激活是一个发生在知觉后加工阶段的具有无意图性的自动化加工过程,刻板印象激活效应具有抑制冲突信息加工同时促进一致信息加工的"双刃剑"模式,N400可以作为考察这一认知过程特征的电生理学指标。

Ample previous studies have provided behavioral and electrophysiological evidences about stereotype activation. It is an open question whether stereotype activation is an unintentional process and what the characteristics of brain activity in this process are. Adopting priming Stroop paradigm, the present study aimed to investigate the pattern and the neural correlates of unintentional stereotype activation by recording both behavioral and ERP data. Thirty young participants （16 female） were recruited in this experiment. The prime word was a social category label （“Men” / “Women”） and a Korean character （“？”/“？”） in the prime and “no-prime” control conditions respectively. The target word was either a stereotypic trait word associated with one of the gender categories or a scene-descriptive word. Thus, the target word was consistent, inconsistent or irrelevant with the gender stereotype. A trial in this experiment began with a 300 ms fixation cross, followed by the prime which was presented on the screen for a period of 300 ms. The prime was followed by an ISI of 500ms, after which the target word came for 300ms. After the presentation of the target a blank was presented and lasted until the participants responded. And then, the inter-trial interval （ITI） was randomized between 600 and 800 ms. All words appeared in the center of the computer screen. The participants were told that 360 words with red, green or blue would appear on the screen in random order. For each word appearing on the screen, they were asked to decide as fast as possible whether a word was red, green or blue by pressing the “Q”,”P” and the “space” button respectively. The button labels of “red”, “green” and “blue” were pasted on the “Q”, “P” and “Space” of the computer key board before the experiment. The responses were counterbalanced across the participants. Behavioral results showed that the reaction time for consistent, inconsistent and irrelevant targets was almost the same in the “no-prime” condition. However, in the prime condition, the participants made significantly faster responses for the consistent targets, compared to the inconsistent; the reaction time for the irrelevant targets was faster than the inconsistent targets but slower than the consistent targets. ERPs results indicated that the N400 amplitude was significantly affected by the target types, but the tendency was obviously different across the prime and the “no-prime” conditions. In the “no-prime” condition, the irrelevant targets elicited the significantly largest N400 amplitude; the N400 amplitudes evoked by the consistent and the inconsistent targets were almost same. However, in the prime condition, the N400 elicited by the inconsistent targets was significantly larger than the consistent targets over the fronto-central area, and the N400 elicited by the irrelevant targets was larger than the consistent targets but smaller than the consistent targets. These results indicated that the process of stereotype activation was an unintentional automatic process. This unintentional stereotype activation effect with “double-edged knife” pattern started at the post-perceptual processing stage and the N400 ERP component reflected the unintentionally access of stereotypical knowledge in the memory representation. The N400 ERP component could be a sensitive indicator to investigate unintentional stereotype activation.