One of the possible functions of displaying emotion is to signal your underlying state. If you are upset, and signal this to your friends with a quivering lip and a lowered head, then they are more likely to perceive your distress, and comfort you. Equally, if you are happy, and signal this with enthusiasm and hugs, then your group can all gain a bit of wellbeing! There is thus a social incentive to externalize your emotions, whether positive or negative.
But what happens when this goes wrong? Supposing a child receives incongruous signals from a parent at a crucial stage of development. For example, supposing a child shows distress, but is consistently met with indifference. They will learn that there is no benefit in displaying their distress, and may even learn to hide that distress, if the parent is unwelcoming or violent. This teaches, very early on, the art of disguising emotion. It explains why children in such circumstances often grow up with an advanced ability to hide what they are really feeling. There is a disjoin between internal feeling and external display.
This can develop even further. Some theorists believe that even false emotional displays can have a social function. We can see this in group behaviour, where individuals often quickly change adapt their behaviour to match the response of their friends, even if that was not their starting emotion. In effect, they are sacrificing their individual response in order to preserve their group identity.
Where someone has learned early to disguise their emotions, this function of false emotion can be misused acutely in adulthood. Adult life can end up being viewed as essentially a game of poker. Social transactions take on the tensions and tactics of a high-stakes game of cards, where each person is perceived as 'selecting' an external display to match a power play, not a true underlying state. In this world, truthfulness takes second place to strategy, and a sense of intimacy is replaced by an awareness of power.
Thus, an adult can emerge who is not sharing who they are inside, but is constantly positioning themselves for maximum defensive effect. They will be afraid of intimacy, and will regard the concept of 'the truth' as relative, to be adapted to circumstances.
You might recognize this profile in many leading businessmen and politicians! Indeed, there is a growing body of literature suggesting that many in positions of power even have psychopathic tendencies. This makes sense when you think that the ability to disguise emotions, and awareness of power plays, are considered core competencies in these fields, and are simultaneously the very skills enhanced by parental indifference and hostility.
So, sometimes, the internal emotion and the external display become divorced from one another. The result can be an adult who does not make friends, only allies. They find it hard to truly share, because they cannot fully trust another person. Their early experience has programmed them to be two people: the inner feeling, and the external display. And it explains why allies can so quickly turn into enemies… friends can be rejected quickly if they cease to be helpful in terms of external objectives, or if they catch a glimpse of the hidden, vulnerable inner self.
How can we change? Firstly, what is probably helpful is a loving and trusting environment, with a consistently low level of threat, so that the defences become redundant. Once the tactics have no purpose, they may be dropped. And secondly, I think we should admit that we all have a little of this ability in us. Everyone develops some ability to moderate their external displays of emotion, in order to manage situations. The aim is to use these abilities for kind purposes. For example, self-restraint in the interests of other people is a sociable form of display modification. I have had situations this year where I have had to work incredibly hard to be patient and restrained, even though my insides were crying out with a sense of injustice and unfairness! However, despite this need to manage our responses, we must never lose the ability to know our own genuine emotions, and share them with others truthfully. That kind of openness and intimacy is the basis of loving relationships.