无意识信息的刺激表征及其时间特性

无意识信息是否存在刺激表征有待解决。实验采用字母Flanker任务, 通过目标和flanker在刺激水平和反应水平上的冲突效应, 重点考察阈下flanker在刺激水平的表征。在相同的实验设计下, flanker可觉察时(实验1A), 观察到经典的刺激冲突效应和反应冲突效应; 而flanker无意识时(实验1B), 重复了反应冲突效应, 却观察到刺激冲突效应发生反转, 提示了无意识信息的反应加工及刺激加工。实验2采用符号材料促使刺激−反应的自动联结, 减少刺激−反应规则的难度, 结果重复了实验1B的发现--无意识信息引起反转的刺激冲突。刺激冲突下反转效应的一致结果表明无意识信息的刺激表征影响了认知加工。实验3考察这种影响在时间进程上的特点。无意识刺激表征的影响随反应时变化：在快速反应中观察到刺激冲突效应, 之后该效应发生反转且反转量随反应时增加而增大。相反, 无意识反应表征的影响在不同反应时下保持稳定。以上结果提供了无意识信息存在刺激表征的行为学证据并揭示了其时间特性, 提供了无意识领域中不一致研究结果的整合思路。

The stimulus representation of unconscious information and its temporal characteristics

The current study reports three experiments to test whether and how unconscious activation of distractors with subliminal presentation, especially at stimulus level, affects response to targets in a letter flanker task. In each experiment, the flanker letters were made unconscious using visually backward masking letters. As classic Flanker tasks, the congruency between target letters and flankers were manipulated to form three conditions – conflicting at stimulus level, conflicting at response level, and non-conflicting. Stimulus conflict referred to trials in which the target and the flankers differed but linked to the same response key, indicating that the competition between the target and flankers occurs at stimulus level. In contrast, response conflict referred to trials where the target and flankers were not only different but also associated with distinct response keys, indicating that the competition between the target and flankers emerges at both the stimulus and response levels. Non-conflict referred to congruent target and flankers trials, used as a baseline condition. Accordingly, the stimulus conflict effect was the difference between stimulus conflict and non-conflict conditions, while the response conflict effect was the difference between response conflict and non-conflict condition. A total of fifty seven participants this study. Experiment 1A was a baseline experiment with supraliminal flankers, in which the classical effects of stimulus conflict and response conflict were observed. However, when the flankers were made unconscious in Experiment 1B using subliminal flankers, a reversed stimulus conflict effect emerged but the response conflict effect maintained. These results were replicated in Experiment 2 when symbolic stimuli were used to reduce the difficulty in forming a stimulus-response association. Likewise, the effects were observed in Experiment 3 with more stimuli and response types were introduced. Crucially, the effect of stimulus conflict dynamically varied along different time windows, while the effect of response conflict was stable across time windows. Altogether, the results provided systematically behavioral evidence for the subliminal activation of distractors that affects target performance at both the stimulus and response levels in a flanker task. The data indicated that the unconscious representation of distractors dynamically influences stimulus processing of targets over time but exerts a stable impact on responses. Our findings, especially the unconscious representation at stimulus level can clarify the mechanism and integrate previous contradicting conclusions of unconscious processing.