The psychology of eye contact, digested

Many of our relationships begin with that moment when our eyes meet and we realise the other person is looking right at us. Pause for a second and consider the intensity of the situation, the near-magical state of two brains simultaneously processing one another, each aware of being, at that very instant, the centre of the other's mental world. Psychologists have made some surprising discoveries about the way that mutual gaze, or the lack of it, affects us mentally and physically and how we relate to each other. Here we digest the fascinating psychology of eye contact, from tiny babies' sensitivity to gaze to the hallucination-inducing effects of prolonged eye-staring.

Our sensitivity to eye contact begins incredibly early. Infants of just two days of age prefer looking at faces that gaze back at them. Similarly, recordings of the brain activity of four-month-olds show that they process gazing faces more deeply than faces that are looking away; and at 7-months, infants' brains process eye contact differently from averted gaze even when the eyes are shown for just 50ms – far too quick for any kind of conscious awareness.

Most children recognise the social significance of eye contact, but they seem to take it too far. At the age of three and four, for instance, they often believe that so long as they cover their eyes – thus preventing eye contact – that they will be completely hidden from view. In fact, children will often claim to be hidden even if they simply avert their gaze while another person looks at them.

Children with autism often show a noticeable lack of eye contact and part of the reason is their difficulty understanding the social significance of another person's gaze, and that they find it difficult to infer other people's mental state from their eyes.

As adults, locking eyes with another person immediately triggers in us a state of increased self-consciousness. Researchers showed this by asking participants to rate their own emotional reactions to various positive and negative images, some of which were preceded by a face staring straight at them, others by a face with gaze averted. Participants had more insight into their own emotional reactions (which were measured objectively through the galvanic skin response) after they'd made eye contact with a face. "Our results support the view that human adults' bodily awareness becomes more acute when they are subjected to another's gaze," the researchers said.

In fact, eye contact is such an intense experience it even seems to consume extra brain power, making it difficult to perform other challenging mental tasks at the same time. This year a pair of Japanese researchers tested participants on a verb generation task while at the same time they looked at a realistic on-screen face that was either making eye contact with them or had its gaze averted. Making eye contact impaired the participants' performance on the hardest version of the verb generation task, presumably because it consumed spare brain power that might otherwise have been available to support performance on the verbal task.

Unlike adults, who mostly know instinctively to break eye contact to help concentrate on what they're saying, children will tend to maintain gaze even when asked a difficult question. Developmental psychologists have shown that children can benefit from being trained to avert their gaze to help them think things through more clearly.

Whether or not other people make eye contact with us changes the way that we think about them and their feelings. For example, we are more likely to remember faces with which we've experienced mutual gaze, and we consider displays of anger and joy to be more intense when shown by a person making eye contact. In fact, when a person or human-like entity (such as a human face morphed with a doll) makes eye contact with us, we assume that he/she/it has a more sophisticated mind and a greater ability to act in the world, such as to show self-control and act morally, and a greater desire for social contact.

Indeed, such is the importance of eye contact to socialising that we tend to form rather low opinions of people who persistently avoid our gaze, assuming that they are less sincere and, at least if they're female, less conscientious. Conversely, we're more likely to believe statements made by a person who looks us in the eye. Yet maintaining eye contact with too much intensity is seen as a feature of psychopaths.

To try to identity the optimum length of unbroken eye contact to make, psychologists recruited participants at London's Science Museum and asked them to rate how comfortable they found different lengths of eye contact made by faces shown in video clips, ranging from between 100ms (a tenth of a second) to 10,300ms (just over ten seconds). On average, the participants were most comfortable with eye contact that lasted just over three seconds.

When it comes to deciding whether we trust another person, it turns out that it's not only a question of how much eye contact they make, but also what we see in their eyes. Remarkably, it seems that we pay attention at a subconscious level to the behaviour of their pupils, and if they dilate – a sign of attraction and emotional arousal – we judge them to be more trustworthy, whereas if they constrict – a sign of fear or feeling threatened – then we judge them less trustworthy. Also, when we trust a partner with dilating pupils, our own pupils tend to mimic theirs and show similar dilation.

We think poorly of conversation partners who consistently avoid eye contact, but it is our feelings of belonging that are hurt when a stranger looks our way and deliberately avoids meeting our eyes – an experience captured by the German expression "wie Luft behandeln", which means to be looked at as though air. Psychologists demonstrated this in a field study on their university campus, in which they subjected passersby to the "wie Luft behandeln" experience after which they reported feeling disconnected from others.

Thankfully we seem to have an inbuilt defence mechanism to avoid these feelings of disconnection when we're already feeling rejected. Psychologists showed us this by prompting some participants to feel ostracised in a game of online ball passing, and then asking them to judge whether a series of faces were looking right at them or not. Compared with control participants, those feeling ostracised were more likely to believe that other faces were making eye contact with them, even if in truth their eyes were slightly averted.

And finally, it seems extreme eye contact can lead to some very strange psychological effects. If you and a partner look into each other's eyes for 10 minutes while sitting in a dimly lit room, you are likely to experience odd sensations that resemble mild "dissociation" – a psychological term for when people lose their normal connection with reality. When the Italian psychologist Giovanni Caputo tested these effects for a paper published in 2015, he found that participants experienced odd feelings of time slowing down, sounds seeming quiet or loud, and 90 per cent said they'd seen some deformed facial features, 75 per cent said they'd seen a monster, 50 per cent said they saw aspects of their own face in their partner's face, and 15 per cent said they'd seen a relative's face.

The meeting of minds and souls that occurs through eye contact can be a wonderful thing, but is perhaps best practised in moderation, or at least in full daylight!