Daniel Kish (blind echolocator): “Ignorance and fear are but matters of the mind – and the mind is adaptable.”
Imagine standing in a dark room – pitch black, silent. Without light, every step feels uncertain, and the absence of visual cues makes it difficult to navigate, until someone clicks on a flashlight. Beams of light slice through the darkness, illuminating the space, revealing furniture, walls, and doors that were previously hidden.
A blind person walks through the same room, clicking their tongue rhythmically. The sound waves bounce back, and the returning echoes carry crucial information about the surroundings: the location of walls, the size of a doorway, or the shape of an object. The brain interprets these echoes, much like how a conductor deciphers musical notes, transforming the sound into a mental map of the environment. This process is called echolocation.
[12] Neidhardt A, Liebal J, Paasonen J. Human echolocation in virtual acoustic environments: Estimating the direction of a close wall. In4th Int. Conference on Spatial Audio (ICSA) 2017 Sep.
The Early Discovery: From Facial Vision to Echolocation
The journey toward understanding echolocation in humans has not been straightforward. In 1749, French philosopher Denis Diderot wrote about a blind friend who could sense objects in the environment without touching them. He hypothesised that blind people could detect subtle changes in air pressure on their face and skin, a phenomenon he called ‘facial vision’ [1,2].
Later research showed that Diderot’s account was actually an early description of echolocation. A key experiment took place in the 1940s in Karl Dallenbach’s lab at Cornell University, in a large room with a vaulted wood-beam ceiling [13]. Two blind and two sighted men, all blindfolded, were asked to walk toward a large masonite board and stop just before touching it. They repeated the task several times, trying to remain as quiet as possible. Surprisingly, all four were able to do this with reasonable accuracy and rarely bumped into the board. When asked how they managed it, three of the participants said they sensed subtle changes in air pressure, what was then believed to be ‘facial vision’. None of them thought they were using sound.
But Dallenbach noticed something important: despite trying to stay quiet, the participants’ hard-soled shoes made noticeable sounds on the hardwood floor. To remove this possible cue, the researchers carpeted the floor, had the participants walk in stocking feet, and played loud tones through headphones to block out any environmental sounds. This time, the participants walked straight into the board every time. When hearing is occluded, echolocation fails.
From Bats to Humans: A Shared Survival Tool
The term echolocation itself wasn’t coined until 1944 when a team of American zoologists lead by Donald Griffin identified that bats could fly effortlessly through dark caves without colliding with the walls, by emitting high-frequency ultrasonic cries inaudible to human ears [1,3]. Griffin’s findings were revolutionary, not only in terms of explaining the extraordinary navigational abilities of bats but also in paving the way for understanding how humans might use similar principles for spatial awareness. Echolocation is not a skill unique to bats alone. Other animals such as marine mammals like whales, dolphins and porpoises, also rely on sonar and echolocation to navigate their environments, locate food and communicate with one another [14].
While some blind individuals may use a combination of tools such as canes or guide dogs to assist with navigation, echolocation can offer far more detailed information about the immediate environment. A cane may detect the presence of a curb, but it cannot provide the shape or size of a tree or window. A broader mental map of the surrounding environment through echolocation can allow blind people to live lives with greater autonomy and precision. Echolocation allows the brain to determine various characteristics of objects, including their distance, location, size, shape, and material [1,2]. The table below provides a visual comparison, but it’s important to note that human echolocation remains an emerging area of research. Therefore, any comparisons or parallels with bat echolocation should be interpreted with caution [15].
| Feature | Humans | Bats |
| Type of sound emission | Audible Sound (20 – 20,000 Hz) [14,15] | Ultrasonic Pulses (20,000 – 250,000 Hz) [14,15] |
| Primary use | Navigation [15] | Hunting/Locating Food/Communication/Navigation [14,15] |
| Level of detail perceived | Can determine location, size, shape, motion, and distance of an object [15] | Can determine location, size, shape, and surface texture of an object [14] |
| Neural processing differences | Visual cortex repurposing (Brodmann Areas 17/18) [15] | Auditory cortex is used as vision remains intact. Echolocation is primarily used for close-range tasks, while vision is especially relied upon during long-distance travel [15] |
The Brain’s Hidden Talent: Neuroplasticity and the Power of Sound
One of the most intriguing aspects of echolocation in humans lies in the ability of the brain to adapt and reorganise itself in response to sensory loss. This concept is known as cross-modal plasticity, and it plays a crucial role in the development of echolocation skills in blind individuals [6-9]. When vision is lost, the brain does not simply abandon the regions dedicated to processing visual information. Instead, it repurposes these regions to process auditory signals, allowing blind individuals to ‘see’ through sound.
Studies using functional magnetic resonance imaging (fMRI) have provided evidence of cross-modal plasticity, with one early-blind patient exhibiting significant activity in the visual cortex. Brodmann areas 17 and 18, which are normally dedicated to processing visual information in sighted individuals, demonstrated increased activity in this patient [2]. Their brain processed auditory input from the echoes in a similar manner to how it would process visual input in a sighted person. Interestingly, this brain activity is not limited to just the visual cortex.
[16] Chebat DR, Schneider FC, Ptito M. Spatial competence and brain plasticity in congenital blindness via sensory substitution devices. Frontiers in Neuroscience. 2020 Jul 30;14:815.
Summary Table of Main Brain Areas by Shared Functional Roles
| Brain Region(s) | Function in Sighted Individuals | Function in Blind Echolocators |
| Medial Temporal (MT) | Processing visual motion | Processing auditory motion |
| Parahippocampus (PHi), Fusiform Face Area (FFA) | Visual processing of an object’s exterior surface material | Auditory processing of an object’s exterior surface material |
| Lateral Occipital Complex (LOC), Infero-Temporal Gyrus (ITG) | Visual processing of object shape and tactile perception | Auditory processing of object shape and tactile perception |
| Occipital Cortex (OC), Posterior Parietal Cortex (PPC) | Visual processing of object location | Auditory processing of object location |
[15] Cooper S, Velazco P, Schantz H. Navigating in darkness: Human echolocation with comments on bat echolocation. Journal of the Human Anatomy and Physiology Society. 2020;24(2):36-41.
Evidence suggests that blind individuals may exhibit greater echo sensitivity than sighted individuals, even in the absence of conscious echolocation use. This heightened sensitivity could introduce complications when comparing brain activation patterns between blind echolocators and blind individuals who identify as non-echolocators [20].
Sight vs. Sound: Echolocation as a Learned Skill
The process of echolocation in humans is not an innate biological trait. Echolocation is a learned skill, a compensatory mechanism that can be developed over time through training and practice [1]. Through deliberate practice usually from childhood, individuals gradually develop the ability to distinguish between different objects based on the echoes that bounce back from them [1]. Some blind individuals become so skilled at echolocation that they can navigate complex environments with ease: travelling through bustling cities, hiking nature trails, or even riding bicycles independently. The brain’s ability to adapt and rewire itself to compensate for lost vision is key to this development. Just as a child learns to walk or ride a bike through trial and error, blind individuals hone their echolocation abilities through repetition.
If echolocation is such a powerful tool, why don’t sighted people use it in the same way? The answer lies in the way the brain prioritises its senses. Our brains are hardwired to rely on vision for spatial awareness. Most sighted individuals do not use echolocation because vision is our best asset for spatial awareness [1,10]. The auditory cortex in sighted people focuses on processing sounds relevant to communication, and filters out echos in the process.
Early-blind individuals, whose brains have had years to adapt to processing sound in place of vision, tend to outperform late-blind or sighted learners [1,5]. Studies assessing how the timing of vision loss affects echolocation skills are limited. One study on 8 late-blind participants suggested that the brain’s ability to adapt to vision loss via cross-modal plasticity depends heavily on when the loss occurs. People who lose their sight early in life often develop more accurate echolocation abilities, likely due to greater brain plasticity during critical developmental periods. This study suggested that the critical period for this type of functional reorganisation ends at age 14 [17].
However, another study challenges the notion that early blindness is a strict requirement for learning echolocation. In a 10-week training programme involving blind and sighted participants aged 21 to 79, researchers found that all participants showed improvement in size discrimination, orientation perception, virtual maze navigation, and natural indoor/outdoor navigation, regardless of age. In some cases, their performance by the end of training was comparable to that of expert echolocators [19]. A major strength of the study was the inclusion of both 12 blind and 14 sighted participants, allowing for meaningful comparisons between the groups. Additionally, a follow-up survey conducted three months later with blind participants added real-world relevance by evaluating the practical impact of training on daily life.
However, the study has some limitations. The small sample size reduces the generalisability of the findings, and the lack of long-term data beyond the three-month follow-up limits understanding of the sustained impact of echolocation training. Further research is needed to explore individual differences and long-term outcomes in greater depth.These findings suggest that echolocation is a trainable skill, although outcomes may vary depending on factors such as training duration, prior experience, and individual brain differences. While the age of vision loss appears to significantly influence the brain’s adaptation to echolocation, the ability to learn the skill is not limited by age. Participants who benefited from the programme reported improvements in mobility, independence, and overall well-being [11].This offers hope for more inclusive and effective rehabilitation strategies for those with vision loss.
The Limits of Echolocation: When Sound Isn’t Enough
Despite its power, echolocation is not limitless. The accuracy and effectiveness of echolocation can be affected by various factors including environmental noise and weather conditions [1]. In noisy environments, such as crowded streets or busy rooms, echoes can be drowned out by ambient noise, making it difficult to interpret spatial information accurately [1,3]. Similarly, certain weather conditions can impede echolocation, such as the way snow scatters sound waves, or absorbs sound differently depending on whether it is wet or dry [1].
Even when echolocation works effectively, social stigma can hinder its use (2). For example, echolocators operating by tongue clicks might hesitate due to the awareness of making loud noises in public spaces [11]. Daniel Kish, an expert echolocator stated that there are those who feel that the clicking draws negative social attention, and there are those who don’t [4]. The stigma surrounding echolocation can prevent its wider adoption, even though it has the potential to empower blind individuals and improve their quality of life. Another important limiting factor is hearing ability. Since echolocation relies entirely on detecting subtle auditory cues, any degree of hearing impairment can significantly reduce its accuracy [1].
The Future of Echolocation: A World of Possibilities
Despite its challenges, echolocation represents a powerful example of human adaptability. The growing recognition of its potential as a tool for independence and mobility has led to increased research and interest in how echolocation can be integrated into assistive technologies [2,11,15]. An example of a prototype assistive device that uses the principles of echolocation is the Sonic Eye. [18]. A speaker on the forehead sends out ultrasonic sounds, these sounds bounce off objects and come back as echoes. The echoes are recorded by microphones on both sides of the head, inside artificial ears (pinnae) designed like bat ears to help figure out direction. The device slows down the sounds into the human hearing range. The current setup of the device is heavy and bulky, so it’s not ideal for daily use yet. A smaller, lighter, low-cost version is being developed with a user-friendly interface for blind users. The device shows promise as a useful navigational tool.
[18] Sohl-Dickstein J, Teng S, Gaub BM, Rodgers CC, Li C, DeWeese MR, Harper NS. A device for human ultrasonic echolocation. IEEE Transactions on Biomedical Engineering. 2015 Jan 16;62(6):1526-34.
Considering sighted individuals rely on peripheral vision and auditory cues to avoid obstacles, blind echolocators are advised to stay aware of their surroundings through a combination of assistive techniques. It is recommended that individuals use echolocation in conjunction with assistive devices, white canes, guide dogs and other strategies for safe navigation [2].
Once considered a rare and mysterious ability, echolocation is now recognised as an extraordinary example of the brain’s capacity to adapt and compensate for sensory loss. Through sound, blind individuals are able to recreate their surroundings in a way that is no less remarkable than the use of vision. Through further study of this fascinating ability, we gain a deeper understanding of the brain’s plasticity and its ability to rewire itself in the face of adversity. Seeing is not just about vision, it is about the brain’s interpretation of sensory information no matter what the source. With the appropriate technological development and social awareness echolocation has the potential to redefine independence for the visually impaired. With the right support, anyone can learn to ‘see’ the invisible, one click at a time.
References
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[15] Cooper S, Velazco P, Schantz H. Navigating in darkness: Human echolocation with comments on bat echolocation. Journal of the Human Anatomy and Physiology Society. 2020;24(2):36-41.
[16] Chebat DR, Schneider FC, Ptito M. Spatial competence and brain plasticity in congenital blindness via sensory substitution devices. Frontiers in Neuroscience. 2020 Jul 30;14:815.
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[18] Sohl-Dickstein J, Teng S, Gaub BM, Rodgers CC, Li C, DeWeese MR, Harper NS. A device for human ultrasonic echolocation. IEEE Transactions on Biomedical Engineering. 2015 Jan 16;62(6):1526-34.
[19] Norman LJ, Dodsworth C, Foresteire D, Thaler L. Human click-based echolocation: Effects of blindness and age, and real-life implications in a 10-week training program. PLoS One. 2021 Jun 2;16(6):e0252330.
[20] Thaler L, Arnott SR, Goodale MA. Neural correlates of natural human echolocation in early and late blind echolocation experts. PLoS one. 2011 May 25;6(5):e20162.
Such an insightful and interesting article! I wish I learnt things like this in school 🤯
This article is truly educational and thought-provoking. There are moments when I encounter someone living with visual impairment and find myself reflecting on their daily experiences. Well done, Etochi Aghamelu, for crafting such an insightful piece 👌.