Who hasn’t ever imagined enjoying the “superpower” of bats? These animals (as well as dolphins, various species of whales and some birds) emit sounds in the form of clicks that bounce off surfaces and bodies in the environment. The returned echo is picked up by specialized organs and processed by the brain. In this way, the animal can obtain information about the distance to different obstacles or prey, their shape, size and identity in order to effectively navigate in its environment. This is known as echolocation, a prodigy of nature on which our sonars are based. But, what if I told you that humans can also enjoy this ability, and in a more advanced way than Batman, who often uses technology to find the bad guys in the dark nights of Gotham?
It is an ability that appears in a more advanced form in blind people. Some of the best known cases are those of the Americans Daniel Kish (1966) and Ben Underwood (1992-2009). Daniel lost both eyes when he was only 13 months old due to bilateral retinoblastoma, a retinal cancer. However, this obstacle has not prevented him from perceiving the world with a high degree of detail through sound. Daniel produces clicks with his tongue and his brain extracts the necessary information from the returned echo to build an extremely accurate representation of the landscape around him, distinguishing the number, size, shape and identity of obstacles that may appear in his path. In this way, Daniel can ride a bike or take a walk in a forest or mountain with absolute nonchalance and enjoying himself as much as anyone else. His mastery of echolocation is such that he was the first blind person to be certified as a guide for other blind people. For his part, Ben lost both eyes at the age of 3, also due to retinoblastoma, and like Daniel, he taught himself to “see” using sound. He was able to distinguish buildings several meters away, to know whether a garage door or car window was open or closed, to ride a bicycle or a skateboard, to play video games. In short, he had another way of perceiving reality without any kind of restriction.
We could also mention Brian Bushway. As journalist and writer James Nestor recounts in his book Deep, Brian managed to guide him through a crowded restaurant to an empty table or to find a free spot in a nearly full parking lot. Blind since the age of 14, Brian was one of the few people after Daniel Kish to be certified as a guide for other blind people.
Science has been studying this phenomenon since the mid-20th century, and has gradually unraveled the mysteries behind these extraordinary abilities. For example, Juan Antonio Martínez Rojas, a tenured professor at the University of Alcalá who has a long history of research into human echolocation, identified the palatal click, the clicking sound generated by placing the tongue on the roof of the mouth just behind the teeth and moving it back and forth rapidly, as the most effective type of sound in human echolocation over any other produced with the mouth or limbs. Furthermore, he assures that anyone, blind or not, can learn to echolocate with sufficient training. Of course, as each person’s auditory system is personal and non-transferable and is adapted to the characteristic sounds that each person emits, each individual has to adapt to his or her own sounds. As if this alone were not incredible, one of his lines of research is focused on the biological limits of human echolocation. The researcher suggests that this sense, if sufficiently developed, would allow the construction of a high-resolution mental image of the landscape, to the point that someone very experienced could detect the activity and presence of some organs in another person or the objects inside a bag. However, it is more difficult for sighted people to access such a high sensory level. It has been shown on several occasions that the echolocation of blind people is superior, possibly due to a more developed hearing ability or because they tend to use this tool on a daily basis and, consequently, have more practice…
We also have information about what happens at the brain level. Although it may seem that the brain regions involved in vision are inactive in blind people, the truth is that they are actually at work during echolocation. It is known that the calcarine sulcus, some parts of the cerebellum and other “visual” regions of the brain are recruited to process the data included in the echoes. The possibility that these regions function differently in a person who is blind because of his or her condition (because of the reorganization of brain areas) would not explain why differential activation of this areas occurs in the presence and absence of echoes, suggesting a direct and precise intervention during echolocation. Interestingly, in sighted people who train echolocation, it is the auditory regions that are stimulated. The functions of the calcarine sulcus and cerebellar regions in these circumstances have not been fully elucidated. One interpretation attributes to them a role of assistance in making spatial calculations from the sound information processed in the regions in charge of sound management.
The applications of this capability are very promising. Imagine, for example, a firefighter expert in echolocation finding survivors in the rubble and dust of a collapsed building by merely using his tongue clicks; a doctor making a diagnosis by listening to the functioning of an organ without the use of any gadget; a person who is lost in the middle of a forest on a foggy day and is able to find his way by listening to the echo reflected on the surface of the surrounding trees and bushes. As we can see, fictional characters like Batman or Daredevil are not so exceptional after all.
Las aplicaciones de esta capacidad son muy prometedoras. Imagina, por ejemplo, a un experimentado bombero ecolocalizador encontrando supervivientes entre los escombros y el polvo de un edificio derruido utilizando meramente sus chasquidos linguales; a un facultativo realizando un diagnóstico escuchando por sus propios medios el funcionamiento de un órgano; a una persona que se ha perdido en medio del monte un día de niebla y es capaz de guiarse escuchando el eco reflejado en la superficie de los árboles y los matorrales del entorno. Como podemos comprobar, personajes ficticios como Batman o Daredevil no son tan excepcionales después de todo.
REFERENCES
Kish, D. (2015, marzo). Cómo uso la ecolocalización para navegar por el mundo [Vídeo]. Conferencias TED. https://www.ted.com/talks/daniel_kish_how_i_use_sonar_to_navigate_the_world?language=es
Moorhead, J. (2007). Seeing with sound. The Guardian [online] January 27, available in: https://www.theguardian.com/lifeandstyle/2007/jan/27/familyandrelationships.family2
Nestor, J. (2014). Deep: Freediving, Renegade Science, and What the Ocean Tells Us About Ourselves. Houghton Mifflin Harcourt.
Pedrós-Alió, C. (2017). Bajo la piel del océano. Plataforma Editorial, Madrid.
Rojas, J.A.M., Hermosilla, J.A., Montero, R.S., Espí, P.L.L. (2009). Physical analysis of several organic signals for human echolocation: Oral vacuum pulses. Acta Acust. united Acust. 95, 325-330. https://doi.org/10.3813/AAA.918155
Schenkman, B.N., Nilsson, M.E. (2010). Human echolocation: Blind and sighted persons’ ability to detect sounds recorded in the presence of a reflecting object. Perception 39, 483-501. https://doi.org/10.1068/p6473
Stoffregen, T.A., Pittenger, J.B. (1995). Human echolocation as a basic form of perception and action. Ecological Physiology 7, 181-216. https://doi.org/10.1207/s15326969eco0703_2
Thaler, L., Arnott, S.R., Goodale, M.A. (2011). Neural correlates of natural human echolocation in early and late blind echolocation experts. PLoS One 6, e20162. https://dx.doi.org/10.1371%2Fjournal.pone.0020162
