The Evolution of Eye Tracking (and the part played by cocaine)
Although eye tracking is viewed as a modern technology, it originated back in the 19th century. At that time the method used was so invasive that anaesthesia with cocaine was required to perform it.
Vision is an important sensory modality for us. Around 80% of all the sensory information we receive is transmitted to our brain via our eyes. Transmission of this visual data also occurs faster than the impressions we receive through our senses of hearing, touch, taste or smell.
With sound
Conveniently for scientists, these visual activities are easy to research. So this has been done for quite some time. One method is “eye tracking”: monitoring the direction of a person’s gaze to determine what they are looking at and how much attention they are paying to it. Though it might seem to be a modern technology, it originated back in the 19th century.
As early as 1879, French researchers Louis Javal and M. Lamare were studying the reading process by tracking eye movements. They did this by attaching a microphone to the reader's upper eyelid. The short, jerky movements made by the eye during reading generated a brief sound. The longer eye movements that were made when passing from the end of one line to the beginning of the next generated a different, longer sound.
With a pinch of cocaine
A few years later, researchers exchanged the microphone for the first eye-tracking device, developed by psychologist Edmund Huey. This was quite invasive: it was a kind of contact lens with an aluminium pointer attached. The pointer changed position depending on the movement of the eye. The method caused so much discomfort to the subjects, however, that Huey anaesthetised their eyes using cocaine.
Another psychologist, Edmund Delabarre, also opted – out of necessity – to use cocaine as an anaesthetic in the method he designed. He used an eye cap made of plaster, with a hole in it to allow the subject to read, and connected this via a wire to a lever that drew a copy of the eye’s horizontal movements. The cast attached itself to the lens of the eye and did not come off until the eye filled with tears.
In the photo
The era of non-invasive (and therefore painless) eye tracking arrived in 1901 with the "Dodge photochronograph" made by Americans Dodge and Cline. They were able to capture the light reflected from the surface of the cornea on a moving light-sensitive photographic plate. What was the downside? The device only recorded horizontal eye movements, and it also only succeeded if the test subject kept their head absolutely still.
This obstacle was partially removed in 1905. At that time Charles Judd found a way of recording all the eye’s movements, in all directions. This worked as long as the head itself remained immobile.
Technological progress
With the advent of the computer, eye tracking became both efficient and comfortable. In the 1960s, two US Army research teams developed mobile eye-tracking technology that processed the data more quickly. By the 1990s these devices were getting better at handling head movements.
Thanks to these technological advances, the range of applications for eye-tracking grew rapidly. Today it is a valuable tool used in all kinds of research that is directly or indirectly related to human behaviour. It is used in various fields – from psychology and medicine, to education and marketing, to media and gaming – and these days we don’t even have to numb our eyes with cocaine.