Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article


Master of Science




Mitchell, Derek G.V.


Using electromyography (EMG), it has been shown that facial muscles imperceptibly mirror the facial expressions of others, a phenomenon referred to as rapid facial reactions (RFRs). It was previously believed to follow the direct-matching hypothesis, however several recent studies have demonstrated that context and individual differences may be influencing factors on RFRs. At the present, it is unclear to what extent RFRs can be modulated. In the present study, we propose to determine the effects of facial stimuli versus non-facial stimuli on RFRs through measuring the EMG response of participants with trait sadism. The participants observed dynamic facial expressions as well as images of limbs in painful situations to assess the specificity of this effect. We found that facial stimuli elicited congruent RFRs whereas the non-facial stimuli did not. This study will allow for a better understanding of the mechanisms of RFRs, which may inform further research on empathy.

Summary for Lay Audience

Rapid facial reactions (RFRs), the experience of replicating others’ facial expressions with your own facial movements, occur in different situations. RFRs occur swiftly, without conscious attention, and are often not visible to the naked eye. Using a technique called electromyography (EMG), facial movements can be measured through electrical currents generated by muscle contraction. While much is still unknown about what can change RFRs, and to what extent, it has been shown that those higher in empathy tend to express RFRs to a higher degree. RFRs are therefore key to understanding the mechanisms behind empathy, and thus are important to study to understand this trait better. Currently, it is unknown if internal emotions are capable of changing these RFRs, and what is capable of eliciting them.

In this study, we attempt to answer these questions. First, to determine if internal emotions are capable of changing RFRs, we aimed to elicit internal emotions that would be different from the observed expressions. If the observed emotion was replicated, then internal emotions could not change RFRs. However, if the internal emotion was displayed instead, this would be called an incongruent emotion, proving that internal emotions could change RFRs. For this purpose, we tested everyday sadism, a trait similar to Schadenfreude in which people high in sadism find pleasure in other’s distress. Second, to determine if faces cause RFRs regardless of internal feelings, we showed participants both facial and non-facial stimuli. The facial stimuli displayed expressions of pain to elicit incongruent reactions in sadistic individuals, and the non-facial stimuli were limbs in pain. If the same RFRs were expressed to the limbs as they were to the faces, then internal feelings likely caused both, but if they are different it may mean that faces have a unique effect on RFRs. We found that there were no incongruent RFRs to pain. The face stimuli elicited a different response than the limbs stimuli, implying that facial stimuli do have a unique effect on RFRs and are not modulated by internal emotions. Overall, this allows us to better understand the nature of RFRs, thereby aiding our understanding of empathy.

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Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.