Eye tracking: what is it, what types are there and what is it used for?

What is eye tracking and how is it used in psychology and marketing research?

It is said that the eyes are the window to the soul, but they also allow us to know how we look at the details of a painting, which parts of our body we look at most when we are in front of the mirror or what catches our attention in an advertisement.

Eye Tracking, or eye tracking, is a process in which eye movements are measured in order to determine where, when and where not to look.This allows us to determine where, what and for how long a person is looking at.

The eyes are perhaps the most important organs through which we obtain information about the world and, for this reason, eye tracking techniques have become increasingly important in research. Let's take a closer look at these techniques.

What is Eye Tracking?

Eye Tracking, also known as eye tracking, refers to the set of techniques that allow us to evaluate where a person is looking, which specific object or detail they are focusing on and how long they keep their gaze fixed.. The devices that carry out this technique are called "eye trackers", and are composed of multiple different types of devices that allow you to focus on the angle of gaze or eye movement itself.

Eye tracking techniques techniques have been used in research in different fields, such as cognitive linguistics, psychology and also in marketing and product design.. They are techniques that allow to know the visual behavior of a person, be it a subject, a patient or a buyer, and based on this to establish conclusions about what their interests are, their emotional state or even if they have some kind of pathology.

History

Although nowadays eye tracking techniques make use of modern devices that allow recording the movement of the eyes or the direction of the gaze, the truth is that the first attempts to know where people looked when doing a certain type of task date back to the nineteenth century. These first attempts were made through direct observation of where the subject was looking, and what kind of information or eye-catching stimulus had been presented to them in their visual field..

Louis Emile Javal, in 1879 it was observed that, when reading, the process of reading did not involve a smooth sweep of the eyes along the text. Until then it was believed that when reading, for example, a book, one followed each line from beginning to end, without jumping or getting "stuck" for a few seconds on a single word. Javal observed that reading was actually a series of short stops, fixations and rapid saccadic movements.

During the 20th century, several questions about reading were attempted to be resolved, such as which words were most often stopped, how much time was spent on them, or how and why one went back and reread words already read. Edmund Huey, with the intention of answering these questions, designed a contact lens with a hole in it. a contact lens with a hole that was placed directly into the participant's eyes.. With these lenses he could record, very accurately, the movement of the eyes when reading, and what was being looked at.

Since Huey's Huey's technique was, although objective and effective, quite uncomfortable and invasiveOther researchers invented their own "eye trackers", which were limited to accurately recording eye movement without the need to introduce anything into the participant's eye. One of them, Guy Thomas Buswell, devised the first non-invasive eye tracking device, using light beams reflected in the eye and, when the eyeball moved, the light beam was deflected, recording the process on film.

During the 1950s and 1960s it was discovered that eye movement, whether in front of a text or an image, could be conditioned by the task to be performed by the participant, or his or her interests. This was the case with the research of Alfred L. Yarbus, who concluded that eye movement not only depended on what was in front of the subject, but also on what the subject expected to encounter.

Today, eye tracking devices have been improved and have become much more precise and less invasive. They have been adapted not only to know the visual behavior of people in front of a picture, a page of text or a face, but also to know what people look at most. Since the 2000s eye-tracking devices have been developed for people with motor disabilities, which interpret the eye movements of people in front of a picture, a page of text or a face.These devices interpret eye movements as commands, causing, for example, a wheelchair to move or a sentence to be uttered by looking at the words on a screen.

Types of eye trackers

Although most eye trackers today are non-invasive and use video recording, they are not the only ones, nor are they, strictly speaking, the most accurate. The following are the three main types of eye tracking.

1. Invasive sensing

Something attached to the eye is used, such as a contact lens with a built-in mirror. This type of eye tracking is quite invasive, as the name suggests, since it involves placing something in the subject's eye that moves according to how the eyeball moves.

As the eyes are delicate organs and, as a general rule, people are very sensitive to being touched, it is not uncommon for them to be touched, it is not uncommon for the participant to refuse to have an invasive sensing eye tracker placed on the eye.. It is a rather annoying technique.

But despite being annoying, eye trackers of this type have the advantage of being able to record eye movement quite accurately, since they move according to how the eye moves. The recordings obtained with this system are very detailed.

2. Non-invasive sensing

This monitoring is done without the need for direct contact with the eye. By means of a light, such as infrared light, the eye movement is detected by the reflection of the light beam, which is captured by a video camera or an optical sensor.

Non-invasive eye trackers usually use the corneal reflex of the cornea. typically use the corneal reflex and pupil center to track eyeball movement.. Others also use the front of the cornea and the back of the lens. Some also record the inside of the eye, looking at the position of the retinal blood vessels.

In general, optical methods are well regarded in the research field, since they are inexpensive and noninvasive.

However, they may fail to record eye movement, since they sometimes do not accurately detect the sometimes fail to accurately detect the pupil, cornea or whatever ocular cues are used for eye tracking. to do the eye tracking. In addition, if the subject closes their eyes, their visual behavior cannot be recorded.

Some virtual reality devices, such as FOVE glasses, have eye trackers of this type, allowing to know to which places the person is looking at once immersed in the virtual environment.

3. Electrical potentials

A rather special eye tracking technique is the one that uses electric potentials, measured with electrodes placed around the eyes.

The eyes are the source of an electric potential field, which can be measured even when the eyes are closed.. The electrodes can be placed in such a way that a dipole is generated, a positive pole on the cornea and a negative pole on the retina.

The electrical signal obtained from this technique is called an electrooculogram (EOG). If the eyes move from the center to the periphery, the retina moves closer to one of the electrodes, while the cornea moves closer to the opposite one.

The main advantage of eye tracking by means of electric potentials is that is able to record eye movement even with the eyelids closed, since the magnetic field of the eye is being recorded.The main disadvantage, however, is that, although it is not completely invasive, it does involve placing electrodes, which means having to scratch a bit.

However, its main disadvantage is that, although it is not entirely invasive, it involves having to place electrodes, which means having to scratch the subject's skin a bit. In addition, the care of these electrodes is quite delicate, and they can fail very easily or not conduct the current well depending on the subject's skin.

Eye Tracking Applications

Eye tracking has been shown to be quite useful for several fields, both theoretical and practical.

Marketing and web design

In marketing eye tracking is a useful a useful technique since it allows to know the visual patterns of the buyers, to know towards which details in an adIt allows us to know to which details in an advertisement, whether on TV, in newspapers or on the web, they look more closely.

Thanks to this, companies can make quantitative studies of how the communication, i.e. their advertisements, are perceived in the population, and how to improve it. Also It is also possible to know the impact of audiovisual advertising, both in a neutral, i.e. experimental, context and in life itself..

By knowing which details users pay more attention to, it is possible to improve company websites to make them more eye-catching and manageable for potential buyers, as well as to keep their attention and direct them towards the purchase of the product or service.

But But eye tracking is not only focused on how to advertise products, but also on how they should be packaged.but also on how products should be packaged. With eye tracking it is possible to see to which stimuli of a certain color, shape or various visual characteristics the subject pays most attention. In this way, companies can design their products and product packaging to induce the purchase of the product.

People with disabilities

Eye tracking has the great advantage of being able to help people with reduced mobility, such as people with tetraplegia or cerebral palsy.

Eye tracking by means of non-invasive sensing can be combined with computer screens, on which letters are displayed that the person can read.The user can look at the letters on computer screens. By fixing their gaze on these letters, a device forms words and phrases that sound through a loudspeaker, enabling people with speech impairments to communicate.

Also This can also be done to get the wheelchair to move. The person stares at the screen, which displays arrows indicating direction. Fixing his gaze on each of these arrows, he sends the command to the mechanized wheelchair to move in the desired direction.

Psychology

By studying visual behavior it is possible to know if a person manifests some kind of pathology, or in what way his or her way of looking at things differs from that expected in a person without a psychopathological diagnosis.

It has been observed that people with attention deficit hyperactivity disorder (ADHD) look off-center much more easily than people without the diagnosis..

This causes them not to pay due attention to elements such as the class blackboard or the textbook, promoting learning and comprehension problems that can be confused, in the most severe cases, with dyslexia or even mental retardation.

It should be said that eye tracking techniques can be very useful for diagnosing both adhd and dyslexia because, although in both there are reading problems, the pattern of visual behavior differs, with the former having more off-center gaze while in the latter there is more fixation on the text, but not very efficient.

Eye tracking has also been used to observe and and analyze the visual behavior of people who suffer from neurodegenerative diseases, such as Alzheimer's, Alzheimer's and Alzheimer's disease.such as Alzheimer's or Parkinson's, and mental disorders such as schizophrenia, autism spectrum disorders, depression or brain injuries.

Of special note is their usefulness in eating disorders. By means of these devices, combined or not with virtual reality, it is possible to know where people diagnosed with anorexia nervosa look the most. Es esperable que centren su mirada especialmente en aquellos lugares en los que más complejo sienten.

Referencias bibliográficas:

• Adler FH & Fliegelman (1934). Influence of fixation on the visual acuity. Arch. Ophthalmology 12, 475.
• Buswell, G.T. (1922). Fundamental reading habits: A study of their development. Chicago, IL: University of Chicago Press.
• Carpenter, Roger H.S. (1988); Movements of the Eyes (2nd ed.). Pion Ltd, London. ISBN 0-85086-109-8.
• Huey, E.B. (1968). The psychology and pedagogy of reading. Cambridge, MA: MIT Press.
• Yarbus, A. L. (1967). Eye Movements and Vision. Plenum. New York.
• Porras Garcia, Bruno & Ferrer-García, Marta & Ghiţă, Alexandra & Moreno, Manuel & López‐Jiménez, Laura & Vallvé‐Romeu, Alba & Serrano, Eduardo & Gutiérrez-Maldonado, José. (2019). The influence of gender and body dissatisfaction on body‐related attentional bias: An eye‐tracking and virtual reality study. International Journal of Eating Disorders. 52. 10.1002/eat.23136.