HUMAN BEINGS show four basic emotions through facial expressions, and not six as previously thought - according to scientists at a leading Scots university.
Happiness, sadness, fear, anger, surprise and disgust are the six basic human emotions which have been thought to be universally recognised and easily interpreted through specific facial expressions, regardless of language or culture.
But now researchers at Glasgow University have challenged this theory, first proposed by American psychologist Dr Paul Ekman, suggesting that humans in fact only show four basic emotions through their facial emotions.
The team from the university’s Institute of Neuroscience and Psychology studied the range of different muscles within the face - called action units - which are involved in signalling different emotions, along with the time-frame over which each muscle was activated.
They claim that while the facial expression signals of happiness and sadness are clearly distinct across time, fear and surprise share the common signal of wide open eyes early in the signalling dynamics.
Similarly, anger and disgust share the wrinkled nose.
It is these early signals that could represent more basic danger signals.
Later in the signalling dynamics, facial expressions transmit signals that distinguish all six “classic” facial expressions of emotion.
The study, published in the journal Current Biology, is the first study to objectively examine the “temporal dynamics” of facial expressions, and was carried out using Glasgow University’s unique Generative Face Grammar platform.
Lead researcher Dr Rachael Jack said today/yesterday [MON]: “Our results are consistent with evolutionary predictions, where signals are designed by both biological and social evolutionary pressures to optimise their function.
“First, early danger signals confer the best advantages to others by enabling the fastest escape.
“Secondly, physiological advantages for the expresser - the wrinkled nose prevents inspiration of potentially harmful particles, whereas widened eyes increases intake of visual information useful for escape - are enhanced when the face movements are made early.
“What our research shows is that not all facial muscles appear simultaneously during facial expressions, but rather develop over time supporting a hierarchical biologically-basic to socially-specific information over time.”
In compiling their research the team used special techniques and software developed at the university to synthesise all facial expressions.
The Generative Face Grammar uses cameras to capture a three-dimensional image of faces of individuals specially trained to be able to activate all 42 individual facial muscles independently.
From this a computer can then generate specific or random facial expressions on a 3D model based on the activation of different Actions Units or groups of units to mimic all facial expressions.
By asking volunteers to observe the realistic model as it pulled various four-dimensional expressions, and state which emotion was being expressed, the researchers were able to see which specific action units observers associate with particular emotions.
It was through this method they found that the signals for fear/surprise and anger/disgust were confused at the early stage of transmission and only became clearer later when other action units were activated.
Dr Jack said: “Our research questions the notion that human emotion communication comprises six basic, psychologically irreducible categories.
“Instead we suggest there are four basic expressions of emotion.
“We show that ‘basic’ facial expression signals are perceptually segmented across time and follow an evolving hierarchy of signals over time - from the biologically-rooted basic signals to more complex socially-specific signals.
“Over time, and as humans migrated across the globe, socioecological diversity probably further specialised once-common facial expressions, altering the number, variety and form of signals across cultures.”
The researchers intend to develop their study by looking at facial expressions of different cultures, including East Asian populations whom they have already ascertained interpret some of the six classical emotions differently - placing more emphasis on eye signals than mouth movements compared to Westerners.