Effects of vicarious pain on self-pain perception: investigating the role of awareness

Abstract

The observation of pain in others may enhance or reduce self-pain, yet the boundary conditions and factors that determine the direction of such effects are poorly understood. The current study set out to show that visual stimulus awareness plays a crucial role in determining whether vicarious pain primarily activates behavioral defense systems that enhance pain sensitivity and stimulate withdrawal or appetitive systems that attenuate pain sensitivity and stimulate approach. We employed a mixed factorial design with the between-subject factors exposure time (subliminal vs optimal) and vicarious pain (pain vs no pain images), and the within-subject factor session (baseline vs trial) to investigate how visual awareness of vicarious pain images affects subsequent self-pain in the cold-pressor test. Self-pain tolerance, intensity and unpleasantness were evaluated in a sample of 77 healthy participants. Results revealed significant interactions of exposure time and vicarious pain in all three dependent measures. In the presence of visual awareness (optimal condition), vicarious pain compared to no-pain elicited overall enhanced self-pain sensitivity, indexed by reduced pain tolerance and enhanced ratings of pain intensity and unpleasantness. Conversely, in the absence of visual awareness (subliminal condition), vicarious pain evoked decreased self-pain intensity and unpleasantness while pain tolerance remained unaffected. These findings suggest that the activation of defense mechanisms by vicarious pain depends on relatively elaborate cognitive processes, while – strikingly – the appetitive system is activated in highly automatic manner independent from stimulus awareness. Such mechanisms may have evolved to facilitate empathic, protective approach responses toward suffering individuals, ensuring survival of the protective social group.

Keywords:

• observation of pain
• approach
• defense
• pain tolerance

Acknowledgments

This project was supported by The University of Hong Kong May Endowed Professorship in Neuropsychology. We would like to extend our utmost gratitude to Prof. Jin Fan, Cognitive Neuroscience Laboratory, Queens College, The City University of New York, NY, USA, and Prof. Xiaosi Gu, School of Behavioural and Brain Sciences and Center for Brain Health, The University of Texas at Dallas, TX, USA, for providing our research team with their previously created and validated set of vicarious pain and no-pain images. We deeply appreciate their contribution without which this research paper could not have been written.

Disclosure

The authors report no conflicts of interest in this work.