认知与发展心理学研究室知识库

与年轻人相比，老年人对于负性情绪的加工能力有所下降，但对于正性情绪并未表现出类似的现象，对正性信息的加工能力维持较好，表现出一定的正性偏向，这称为年龄相关的正性效应(age-related positivity effect)。很多学者针对该现象提出了相应的理论解释，但其产生机制仍然存在很多争议。一些研究者认为只有当认知资源充分时，老年人对于表情的加工才会表现出正性效应(Knight etal., 2007; Isaacowitz et al., 2010; Reed & Carstensen, 2012 )。但正性效应并不一定完全依赖于晚期的认知控制，在早期的表情加工阶段也会出现(Johnson & Whing,2013; Hilimire et al., 2013)。

本论文针对上述争论，设计了两个研究，考察表情加工正性效应的产生机制。研究一分别从控制加工和自动加工两个角度考察了阈上内隐表情加工的正性效应。实验1采用负启动实验范式，发现老年人对启动项负性分心物的抑制更强，导致对探测项负性靶刺激的效价判断错误率表现出更高的趋势;对正性分心物存在加工偏向，对探测项正性靶刺激的判断反应时更快。年轻人对靶刺激的判断受到启动项负性分心物的影响，表现出对负性分心物的加工偏向。老年人在无关表情的加工上表现出正性效应，而这种效应并非老年人认知衰退引起的。实验2采用表情启动范式，发现老年人对中性面孔的判断受到正性启动面孔的同化，将中性目标面孔更多判断为正性。年轻人在对情绪面孔的加工上也表现出同化现象，但没有情绪效价效应。此外，结果发现内隐表情加工的正性效应主要体现在男性群体上:男性老年人表现出正性加工偏向，男性年轻人没有表现出情绪偏向;女性老年人和年轻人均表现出正性加工偏向。

研究二主要探讨无意识表情加工是否存在正性效应。实验3和4利用连续闪烁抑制范式(continuous flash suppression)分别从行为和ERP上考察无意识表情加工的正性效应。实验中，向被试的优势眼阂上呈现中性面孔，同时非优势眼阈下呈现愤怒、高兴或中性面孔，被试的任务是判断阂上中性面孔的热情度。结果发现:(1)行为上，老年人对于阈上中性面孔的热情度评分受到阈下高兴表情的影响更大，而年轻人的评分并没有受到阈下表情效价的影响。这表明老年人和年轻人对于无意识的表情自动加工表现出不同情绪偏向模式:年轻人没有明显的情绪偏向，而老年人表现出正性偏向，老年人表情加工的正性效应在无意识的自动加工中就出现了。(2)时间进程上，相比于阈下中性表情，阈下负性表情诱发的老年人的P1波幅更小;老年人无意识正性效应主要体现在晚期正成分LPP上，阈下正性表情相比于中性、负性引发了老年人更大的LPP波幅，而年轻人的LPP波幅没有受到情绪效价的影响。

综合上述两个研究四个实验的结果以及相关讨论，本研究可以得到如下结论;

(1)老年人表情加工正性效应不完全依赖于认知控制，也存在于无意识的自动加工中;

(2)表情加工正性效应的两个方面一对正性的偏向和对负性的回避可能存在不同的认知机制:对正性的加工偏向更多是情绪目标导向的，对负性的回避可能受到脑功能衰退的影响;

(3)表情加工的年龄变化存在性别差异:老年人女性和大学生女性都存在对正性表情信息的加工偏向;男性老年人的表情加工表现为正性效应。这一结论至少在表情同化中适用。

Age-related positivity effect refers to a relative preference in older adults (compare to younger adults) for processing positive over negative emotion. Some theory models have been proposed to account for age-related differences in emotional processing, but the neurocognitive mechanism of this effect remains controversial Some studies suggest that positivity appears only when cognitive resources are adequately available (Knight et al., 2007; Isaacowitz et al., 2010; Reed & Carstensen. 2012). In contrast, other studies suggest the positivity effect can occur at earlier automatic process, and cognitive control is not always necessary (Johnson & Whing, 2013; Hilimire et al., 2013).

In the present research, we investigated the mechanism of age-related positivity effect of facial expressions, via two studies.

Study 1 investigated on the positive effect of the supraliminal implicit expression processing from two views of inhibition and automatic process. Experiment 1 using negative priming paradigm, found that elders showed more inhibition to negative distractor which led to high error rates, a preference to processing positive expressions that led to slower response time. Young adult was affected by the priming negative distraction, showed a negative distraction processing bias. Age-related positivity effect observed here is not due to the cognition decline.

Experiment 2 using priming paradigm found that influence by the positive priming faces, elders more judged the neutral targets as positive. Young adults were also influenced by emotional faces, but not by different valences. In additions, the positive effect of implicit expression processing mainly reflected on men: men showed positive processing bias in the elderly, young men did not show the emotional bias; while, older women and young women showed a positive processing bias.

In study 2, we examined whether this age-relate positivity effect occurs in the unconscious emotional processing using continuous flash suppression (CFS) paradigan and El2P methods. In the experimental task, two facts were simultaneously displayed, but neutral target face was supraliminally presented to the dominant eye and emotional (happy/neutral/angry) distractor face was subliminally projected to the non-dominant eye. Participants were instructed to judge how warm the target fact was. The results showed that (1) the warmth ratings of elders increased with the invisible positive faces, whereas the ratings of younger adults remained independent of emotional distractor faces. These findings provide additional evidence that the age-related positivity effect can be traced to automatic processing of emotional facial expression, indicating the positivity sensitivity in unconscious emotional processing of elders; (Z) the amplitude of P1 of elders was smaller under negative condition than neutral condition9 and the amplitude of LPP of elders was larger under positive condition than neutral/negative condition. However, the amplitude of LPP of young adults in different conditions had no difference.

According to these experiments, the conclusions were as follows:

(1) Positivity effects in emotional processing did not rely fully on cognitive control, also could occurred in unconscious automatic processing.

(2) There may be different cognitive mechanism in two aspects of positivity effect- the positive bias9 and avoidance of negative information: Positive bias was more oriented by emotional goals9 while avoidance of negative may be affected by brain function decline.

(3) There were gender differences in age changes of emotion process: the elderly women and college students showed positive bias. However, there was a shift toward preferentially processing positive information in older men. This conclusion could, at least, be found in the expression assimilation processing.