Facial feedback hypothesis

The facial feedback hypothesis states that facial movement can influence emotional experience. For example, an individual who is forced to smile during a social event will actually come to find the event more of an enjoyable experience.

Charles Darwin was among the first to suggest that physiological changes caused by an emotion had a direct impact on, rather than being just the consequence of that emotion. He wrote:

The free expression by outward signs of an emotion intensifies it. On the other hand, the repression, as far as this is possible, of all outward signs softens our emotions... Even the simulation of an emotion tends to arouse it in our minds.

Following on this idea, William James proposed that, contrary to common belief, awareness of bodily changes activated by a stimulus "is the emotion". If no bodily changes are felt, there is only an intellectual thought, devoid of emotional warmth. In The Principles of Psychology, James wrote: "Refuse to express a passion, and it dies".

This proved difficult to test, and little evidence was available, apart from some animal research and studies of people with severely impaired emotional functioning. The facial feedback hypothesis, "that skeletal muscle feedback from facial expressions plays a causal role in regulating emotional experience and behaviour", developed almost a century after Darwin.

While James included the influence of all bodily changes on the creation of an emotion, "including among them visceral, muscular, and cutaneous effects", modern research mainly focuses on the effects of facial muscular activity. One of the first to do so, Silvan Tomkins wrote in 1962 that "the face expresses affect, both to others and the self, via feedback, which is more rapid and more complex than any stimulation of which the slower moving visceral organs are capable".

Two versions of the facial feedback hypothesis appeared, although "these distinctions have not always been consistent".

According to Jeffrey Browndyke, "the strongest evidence for the facial feedback hypothesis to date comes from research by Lanzetta et al. (1976)" (but see "Studies using Botox" below for more recent and powerful evidence). Participants had lower skin conductance and subjective ratings of pain when hiding the painfulness of the shocks they endured, compared with those who expressed intense pain.

However, in all research, difficulty remained in how to measure an effect without alerting the participant to the nature of the study and how to ensure that the connection between facial activity and corresponding emotion is not implicit in the procedure.

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