From evolutionary perspective, such ability is crucial for our social functioning. It allows for recognising and avoiding threat; for establishing friendships/romantic relationships, etc. We can extract a hell lot of information about a person just by looking at their face:
3. Emotions/thoughts (through facial expressions)
4. Eye gaze - mutual attention
5. Lip reading
In this post I will discuss such topics as anatomy and neurology of face perception; facial expressions; innateness of face perception ability and deception.
Anatomy of face perception
Region of the brain responsible for processing unchangeable aspects of people's faces is called fusiform gyrus, which is located in temporal lobe in Brodmann area (marked with a star at the picture). When I say 'unchangeable aspects', I mean that this area is responsible for relating a face to a specific person; in other words, for identification.
There is another brain region involved in face recognition: superior occipital gyrus (bottom right at the picture). On contrary, it processes changeable aspects of a face (face expressions, angles etc.)
Measuring face perception
In 1978, Ekman and Friesen devised a Facial Affect Coding Scheme (FACS). FACS is a system which aims to categorise facial expressions. According to it, there are 33 small individual movements called action units which can be combined in 44 different combinations to form a recognisable face expression. Every action unit has its code in the system, thus every expression can be described in a following way: Happiness = 6 + 12; Anger = 4+5+7+23 etc.
The system also includes codes for the head position and eye movements. At the picture here, action units for eyebrows are illustrated.
Anatomy and neurology of face expressions
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There are two main types of expressions: spontaneous (that is, natural) and posed (superficial, forced). Both of them are produced by the facial nerve Nucleus, which is situated in pons. However, two different routes are at work:
Route 1: spontaneous expressions. Emotional arousal activates hypothalamus (responsible for motivation and arousal) and limbic area (our emotion centre); then the signal is sent to nucleus through extrapyramidal tract.
Route 2: posed expressions. Motor cortex sends a signal to Nucleus through pyramidal tract.
How can we tell one type of expression from another?
1. Posed expressions are typically asymmetrical, with left-hand side of the face being more pronounced. It happens because motor cortex which activates posed expressions is situated on the right side of the brain (meaning it has more effect on left side of our body).
2. Genuine expressions are symmetrical, as they are produced by limbic cortex.
Innate nature of facial expressions
Ekman (1982) conducted a global cross-cultural study which involved participants from the USA< Chile, Argentina, Brazil and Japan. He found cross-cultural similarities in both encoding and decoding facial expressions - however, only when they were produced by the Route 1, spontaneous expressions. The only expressions which were somewhat difficult to decode were fear and surprise.
Route 2, however, allowed for cultural differences in the amount and contextual appropriateness of facial expressions.
Thompson (1941) studied blind and sighted infants, and found that expressions produced by the route 1 were, indeed, innate: the infants could not see others smile, however did so themselves.
Other infant studies showed that newborn babies all show similar expressions: disgust, smiles, crying etc - however, all these expressions are reflexive, and do not function as a way to interact with the world. At about 3 months, infants start smiling at faces, reacting to the environment around them. At 4 months they demonstrate anger, and at 6 months - fear. Development of expressions encourages further cognitive developments, as infants' reactions to stimulation provokes more stimulation on the part of caregivers and parents. Here, it is important to highlight the significance of contingency in expressions development: infants need to see the effects of their smiles and other expressions in order to use them appropriately to situation.
In 1979, Saarni conducted a research in which he found that 10 years old children were less likely to demonstrate their disappointment than 7 years old, as they did not want to upset the researcher. It suggests that display rules are acquired with age and experience.
However, it is not an issue of age only: display rules vary from culture to culture. In 1972, Friesen asked participants from Japan and the USA to watch a video of sinus surgery. Participants watched the video in solitude, but were filmed. Irrespective of country of their origin, all the participants showed an expression of disgust while watching video. Later they were interviewed and asked some questions about the video. Americans, once again, showed disgust, while participants from Japan retained happy facial expressions.
Therefore, it seems fair to say that spontaneous facial expressions are innate: studies of infants and cross-cultural studies seem to support such notion. However, posed expressions are regulated by display rules which are learned; these rules are responsible for most cultural differences.
What are the signs of the routes being in conflict?
> Asymmetrical expressions
> Facial expressions are not synchronised with other body movements; body movements are harder to control than facial cues
> False smiles do not effect upper part of face!
> Quick offset and end of an expression
> Raised pitch
> Overcontrol of blinking/gazing/body movement
> Less gaze avertion (remember the previous post? people assume gaze aversion is a sign of lying, so they often make an extra effort NOT to avert their gaze while lying)