The Pupil

How the Pupils Dilate in Response to Emotional States

The pupil is the black centre of the eye which opens or closes to let in more or less light. It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil.

The pupil
The Pupil

Pupils respond to three distinct kinds of stimuli: they constrict in response to brightness (the pupil light response), constrict in response to near fixation (the pupil near response), and dilate in response to increases in arousal and mental effort, either triggered by an external stimulus or spontaneously (Sebastian Mathot, Pupillometry: Psychology, Physiology, and FunctionOpens in new window).

Darkness causes pupils to dilate. So too, for some reason, does seeing something appealing or attractive. Most descriptions regarding the ‘look’ of one’s eyes have to do with the pupils. It is not always possible to get close enough to a person to observe the pupils clearly.

Pupils are the only part of the body that are uncontrollable. Unlike any of the other body languageOpens in new window gesturesOpens in new window that are unconscious but still controllable if someone is aware, pupils will act on their own contracting and dilating based on the light conditions.

Pupils also automatically dilate and contract in accordance with the attitudes and changing moods of a person. Our pupils dilate when we experience a positive emotion and contract when we experience a negative one.

In other words, pupils dilate when we are interested in an object or in what the other person is saying. Of course, we encounter the opposite too, when we are uninterested, our pupils shrink. Try watching the change in the size of a friend’s pupils closely as a conversation moves from an interesting topic to a duller topic.

When our pupils dilate, we are totally unaware of the information that we are providing about our emotional state. What is equally interesting is that people who see us, and who recognize our heightened state of arousal, do not know how they came to that conclusion—they know there is something attractive about our face, but they cannot identify what it is.

In other words, when our pupils dilate, we produce a genuine clue, but we do not know that we are doing it. At the same time, other people react to the clue but they do not know why (Collett, 2003).

In pupillometryOpens in new window, an area of scientific investigation (Sussman and Deep, 1989), changes in pupil configuration as a function of emotional arousal are examined. When registering positive moods in favourable situations, like interest and excitement of some kind, the pupils of the eye can dilate up to four times their size.

When registering negative sentiments in unfavourable situations. Like anger, boredom, and disinterest, they contract considerably, to what are ordinarily regarded as ‘beady little eyes’ or ‘snake eyes’. The pupils thus reveal actual feelings.

So, by observing the pupils—which is not an easy task—when we look at a person ‘eye-to-eye’ while communicating we can figure out what is going on inside the person.

Infants and children have larger pupils than adults; their pupils constantly dilate when there are people around, so that they appear as appealing as possible and thus attract attention.

Young lovers tend to look deeply into each other’s eyes. Unconsciously, they search for reactions in the pupils. When either or one of the partners is excited, the pupils get dilated. Some people wear dark glasses in order not to let their eyes betray their real emotions.

The studies made by Hess (1975) generated a lively interest in ‘expressive eyes’. The studies revealed that pupil dilation or constriction was an extremely accurate indicator of the person’s response to stimulation. According to his conclusion, the pupils dilate when a person is interested or aroused.

For instance the pupils of a man’s eye enlarge to twice their size when he sees a pornographic movie, while the pupils of women dilate to almost three times the normal size when she sees the same.

When faced with unpleasant or repulsive stimuli, the pupils constrict. Knowledge of this has led some ‘glamour’ photographers to enhance their models in the same way and thus increase their attractiveness.

A subtle signal that is sometimes detected only subconsciously and is seldom realized by the sender is where the pupil gets larger (dilates) or contracts.

Sexual desire is a common cause of pupil dilation; what is known as ‘gazing deep into each others eyes’ is an unconscious way of looking for pupil dilation in the other to get excited if we see it.

When another person’s eyes dilate, we may be attracted further to them and our eyes dilate in return. Likewise, when their pupils are small, ours may well contract also. The reverse of this is that pupils contract when we do not like the other person, resulting in a squint-like narrowing of the eyes.