New research from the University of Essex has revealed that smiling for just a second makes people more likely to see happiness in expressionless faces.

Research led by Dr. Sebastian Korb from the Department of Psychology shows that even a slightly weak smile makes the face happier.

An early experiment used electrical stimulation to induce smiles and was inspired by Charles Darwin’s famous photographs.

A painless current moved the muscles momentarily — producing a brief uncontrollable smile.

This is the first time that electrical stimulation of the face has been shown to influence emotional expression.

Dr. Korb hopes the research could lead to potential treatments for depression or disorders that affect expression, such as Parkinson’s and autism.

He said: “Finding that a controlled, brief and weak activation of facial muscles can literally create the illusion of happiness in a neutral or even slightly sad looking face.

“This is relevant to theoretical discussions about the role of facial expressions in emotion perception and has potential for future clinical applications.”

Dr. Korb used a modern version of a technique first developed in the 19th century by French physician Duchene de Boulogne.

Darwin published drawings of Duchenne’s work in The Expression of Emotions in Man and Animals – his third major work on evolution.

However, for the new experiments the voltage was dialed down to ensure participant safety and to better control the smiles.

Using computers, the team was able to control the onset of smiles with millisecond precision.

A total of 47 people participated in the Essex study, which was published in Social Cognitive and Affective Neuroscience.

They were shown a digital avatar and asked to rate whether they were happy or sad. In half of the trials, the smiling muscles were activated at the onset of the face.

It turned out that producing a weak smile for 500 milliseconds was enough to induce a feeling of happiness.

Dr Korb says the findings help us understand facial expressions and he hopes to expand the study.

He said: “We are currently conducting further research to further explore this phenomenon in healthy participants.

“However, in the future, we hope to use this technique to explore facial emotion recognition in people with conditions such as Parkinson’s, who are known to have spontaneous facial mimicry and Recognition of facial emotions is reduced.

“In addition, we have published guidelines to allow other researchers to safely use electrical facial muscle stimulation.”