Subliminal Presentation Of Emotional Expressions With Other-face And Self-face And Its Effects On The Perception Of Other-pain Expressions

Emotion and pain are features of a larger motivational system associated with overlapping areas of the cerebral cortex (Rhudy and Meagher,2001). Consequently, alterations in emotional experience could alter the perception of pain. Previous research on the modulating effects of emotion on pain perception indicated that negative affective experiences augments pain perception and positive affective stimuli attenuate pain. Nevertheless, most of this research focused on the perception of self-pain experiences rather than the perception of vicarious other-pain. Painful facial expressions are highly salient (Craig,1992) may prompt observers to provide social support for the sufferer or to escape or avoid such cues as a means of protecting themselves from potential threats (Williams,2002; Yamada and Decety,2009). Behavioral and neuroimaging studies have found higher pain intensity ratings for sensory pain are related to presentations of painful faces compared to other negative-affective faces such as anger and fear. However, the manner in which painful faces modulates the perception of other-pain is unclear.The present research attempted to assess the modulating effects of facial expressions of emotion, and specifically painful facial expressions, on perception of subsequent painful expressions via an affective priming paradigm. The affective priming paradigm was widely employed to investigate how affective stimuli such as words or pictures influence judgments of subsequent word-related tasks. Further research has extended affective priming paradigms to examine the affective priming effects on the evaluation of emotional faces, with happy expressions as positive primes and angry or fearful expressions as negative primes. Researchers have suggested that affective primes generally facilitate responses to subsequent valence-congruent targets relative to valence-incongruent targets.Further, painful expressions subsume both semantic and affective properties and are considered expressions as well as emotional-communicative cues. To control for semantic priming effects of painful expressions, this research presented all facial emotion expression primes subliminally to evaluate affective priming effects of painful facial expressions. In addition, both self-faces of participants and other-faces of unknown others were employed as painful primes in the present research, which made it possible to compare the affective priming effects of self-versus other-face primes. Altogether, three studies were conducted to investigate (1) affective priming effects of emotional faces on perception of other-pain expressions; (2) whether priming effects differed as a function of self-face or other-face primes and (3) whether the priming effects differed under subliminal and supraliminal presentation conditions that featured self-face primes.In Study 1, happy, neutral and painful expressions were used as primes and neutral and pain expressions as targets to investigate the subliminal priming effects of emotional faces on pain perception of other-face expressions. Twenty-six undergraduate students were recruited and instructed to rate the pain intensity of facial expressions presented on the computer screen following the subliminal presentation of each prime type. Both reaction times (RTs) and pain intensity ratings were recorded as the dependent variables. Resulted showed that neutral expression primes predicted faster RTs and higher pain intensity ratings for neutral targets than happy and painful expressions primes; painful expression primes were found to increase pain intensity ratings for painful targets but not reaction times relative to happy expression primes.In Study 2, a Chinese Facial Emotional Expression Set consisting of happy, neutral, fearful and painful facial expressions was developed and validated within young adult samples. Subsequently emotional facial expressions from the Expression Set were employed as self-face primes and other-face targets in subsequent behavioral studies. Study 2 was conducted with the same procedure as Study 1 and found that both fearful and painful primes predicted faster RTs for painful targets than neutral primes, which did not differ from happy primes. Neutral primes, as well as happy primes, predicted faster RTs for neutral targets than both fearful and painful primes. However, pain intensity ratings for other-face targets did not differ as a function of happy, neutral, fearful and painful expression primes.Study 3 included two sections of subliminal and supraliminal presentations. Neutral and painful facial expressions of new comers were obtained as self-face primes and neutral and painful expressions randomly selected from the Expression Set were used as other-face targets. The procedure of Study 3 was similar to the first two experiments except that the subliminal priming section was always performed in advance of supraliminal priming section. Results demonstrated that, for both subliminal and supraliminal presentations, painful primes predicted faster RTs and lower pain intensity ratings for painful targets than neutral primes.In summary, although Study 1 failed to find facilitative effects of pain face primes on pain face targets, face expression primes were based on out-group Caucasian faces rather than inter-group Asian faces. To address this limitation, a facial expression image set featuring Chinese males and females was created. When using Chinese facial expressions as primes, painful facial expressions facilitated RT to painful face targets in two independent samples of Chinese undergraduate students (Study 2 and Study 3). As such, these findings are consistent with selected facts of general predictions regarding the impact of negative emotional primes on affectively-congruent targets (Lang,1995; Fazio et al.,1986). On the other hand, findings were inconsistent regarding the impact of painful primes on judgments of pain intensity. Though Study 1 and Study 3 suggested that painful primes predicted lower pain intensity ratings for other-pain expressions compared to neutral primes, Study 2 failed to confirm the affective priming effects of self-face primes on pain intensity ratings for other-face expressions.