Blog: Understanding EYE-SYNC through Optocentricism
As humans thrown into the world, how do we interact with our surroundings? While we certainly may touch and taste things, these require the intimacy of contact. As we push further afield from the borders of our bodies, we may also access information through smell, though that too requires proximity for molecules to find their way to us. Moving even further out from ourselves, we access the world via traveling waves that are interpreted by the oscillation of drums and fibers in our heads in kind. But most importantly, to access the world in its richest resolution, its furthest biological reach, and its most resplendent way, we as humans turn to sight.
As optocentric animals, that is animals driven primarily by their ocular system, we have a unique position in the world. Many animals are not motivated in this way, a dog would be more olfactocentric, while a bat would be sonocentric. This may seem fairly obvious, but is often overlooked or outright disregarded in scientific discourse. The assumption of optocentrism in other species is best evidenced by theories of consciousness that require animals, like dogs, to self identify in a mirror. The first of these experiments were devised by Gordon Gallup in the 1970s, wherein he was able to successfully get chimpanzees and orangutans to recognize themselves in the mirror. Few other species are able to self identify with a reflection, with some notable exceptions like bottlenose dolphins who were added to the list in 2001 by experimenters Diana Reiss and Lori Marino. When compared to animals that fail the task such as dogs and cats, passing animals like dolphins, chimps, and orangutans are touted as having a higher form of intelligence for this accomplishment of happenstance. Lack of visual self-identification is usually taken to indicate the species in question have less or no conscious internal world, but if the tables were turned and we were asked to identify ourselves by smell, most humans would likewise fail and therefore be seen as unconscious to these hypothetical canine or feline scientists.
The varying predispositions of sensory integration build very different internal lives for the creatures in question. Thomas Nagel puts forth a wonderful cross-species illustration of how differing sensory modes will build different internal models in his landmark exploration “What Is It Like to Be a Bat?”. Importantly, the variance of sensing ability is not just a cross-species question, but can even be applied to differences in sensory dominance in different humans. Frank Jackson dives into this question in his thought experiment Mary’s Room, wherein Mary lives in a black and white space her whole life and is then exposed to a world of color. The question of epiphenominal qualia, or windows onto the world derived from the phenomenal experience of the world, is complex and understudied.
The human disposition toward sight feeds back on physiology and has resulted in a huge dedication of resources to a physically demure system. Estimates of human brain energy consumption often peg the organ as taking up some 25% of energy in the body in spite of it being only 1-2% of the overall size. Another outsized impact can be seen when analyzing the oculo-visual systems of the human brain, which in turn consumes a disproportionate percentage of overall cerebral resources. In particular, predictive attention and use of smooth pursuit eye movements are very power hungry processes. Of the 86 billion neurons in the entire brain, some 80% reside in the cerebellum, the throne of timing and predictive visual attention. Remarkably, at birth none of these cerebellar neurons are connected, but as mammals play, explore, and interact with their environment, the neuronal granule cells descend and interconnect. This development is in service of creating an internal clock, a sense of timing and prediction, and is primarily generated through oculomotor and oculovestibular data.
Because oculomotor function is so resource intensive, any disruption to normal brain function via an impact, sleep deprivation, pathology, or pharmacological impairment has an outsized impact on the functioning of this system. Additionally, the oculomotor attention system is the most conspicuous and straightforward to interact with in humans as there is an obvious change in the position of the eye relative to the object of attentional import. It is hard, if not impossible, to measure the level of human auditory attention granularly as the eardrum is not exposed to the outside world. Were human physiology different and dependent on pivoting ears like dogs, we may stand a better chance of measuring attention from a purely auditory point of view.
The proposition of putting metrics to human attention was first explored by Benjamin Libet in his foundational tap-response experiments. Herein, subjects were implanted with deep brain sensors that were able to detect changes in the electric potential of the organ. These subjects were then tasked with conducting a tap in sync with a clock. Dramatically, Dr. Libet found that the activity of their brain spiked not only at the moment wherein the finger was directed to tap, but also well before there was any conscious decision to tap. This preconscious activity has manifold implications for free will and has sparked a diversity of debate, but importantly it also offers a clear window into the way the brain interacts with the world, through prediction.
While Libet’s experiment is very elegant, it is a haptocentric solution, which makes it suboptimal. While the subjects were measuring the target (in this case the hand of a clock) with their ocular system, the forward fed response from the brain to this question of timing was highly delayed as the signal had to physically travel a few feet from the brain to the finger, with an ultimate delay of over 250 milliseconds.
Eye tracking, a technology unavailable to Libet at the time of his experiments, tightens this interaction loop. Here, the brain’s signaling not only occurs in a physically closer pathway, it also is in control of a much more granular and detailed set of movements. Eye tracking is able to take advantage of the fovea, the pinpoint window each eye has onto the world. In an act of memesis, we take that which typically looks out, and turn it back on itself to look in. Rather than the eyes being the window to the world, by using eye tracking, we can open them up to be the windows to the brain.