Spring 2019 > Research Excellence

Blind as a Bat?

What comes to your mind when you see a cloud of bats? An image of nefarious, vampire-like creatures? Or adorable, nocturnal fliers? The perception of bats has always been polarized, but no one would disagree that they are unique.

Bats have their own taxonomic group, the order Chiroptera, and are the only true flying mammals. As portrayed in horror movies, bats really do hang upside down and live in dark caves. What most people do not know, however, is that there are more than 1,200 species of bats. Like bees, they pollinate plants; like frogs, they eat insects; and above all, they are not blind! Bats can see with the aid of “sound” using sonar-like “echolocation”—a term coined by the late Dr. Donald GRIFFIN, an American zoology professor and biopsychologist whose expertise lay in animal behavior and navigation, acoustic orientation, and sensory biophysics.

Prof. Cynthia MOSS, Professor in the Departments of Psychological and Brain Sciences, Neuroscience and Mechanical Engineering at Johns Hopkins University, and IAS Senior Visiting Member, is batty about bats. Her bat laboratory is equipped with high-speed cameras and voice recorders to capture the flying motions, flight paths, and most importantly the high-frequency sounds of echolocating bats. The purpose is to study the natural, sensory-guided behaviors of these animal models and how they process information about the environment using echo returns from ultrasonic emissions.

Seeing Through Sound

In her IAS Distinguished Lecture “A Glimpse of the World through the Voice of a Bat” held last November, Moss presented some key discoveries on bats’ adaptive echolocation behaviors and their diversity of signal designs, which are crucial in a variety of tasks. She noted that humans can hear sound up to ~20 kilohertz (kHz) whereas bats can hear ultrasonic sound (>20 kHz) inaudible to human ears, which reflects off small objects, to intercept prey, avoid obstacles, and discriminate targets.

According to Moss, bats have the ability to sort echoes from various objects and shift the distance of their “acoustic gaze” from obstacle to target. “The success of bat echolocation depends largely on their ability to modify their sound emissions in response to information that they receive and to seek a specific kind of information from the environment. There is an adaptive adjustment during echolocation.”

Prof. Moss added that “bats are able to measure distance and to separate and assign echoes to locate targets. Their tragus, which is part of the external ear, influences the spectral profile of the returning echo and plays a pronounced role in bats’ vertical sound localization of sonar targets. However, not all bats use echolocation—some of them have excellent eyesight.”

A Human Echolocator

In the lecture, Moss introduced a video featuring Mr. Daniel KISH, who has been blind since the age of 13 months and taught himself to “see” using tongue clicks—a form of echolocation used by Egyptian fruit bats.

Kish is the founder of World Access for the Blind, a nonprofit organization that facilitates “the self-directed achievement” of people deprived of sight. His remarkable ability to echolocate by using mouth clicks, sending out flashes of sound that bounce off surfaces in the environment and return to him, has earned him the nickname “real-life Batman.”

Like a bat, Kish uses echolocation to paint rich landscapes of the space around him inside his mind. As an expert echolocator, he can even ride a bike on the street as confidently as anyone with normal vision. “I am able to construct images from surfaces in the environment based on sonar,” said Kish. His echolocation ability allows him to sense not only objects’ position and shape but also their particular qualities.

Moss emphasized the many similarities between what Kish does (lingual echolocation by blind humans) and what Egyptian fruit bats do. In an experiment carried out by Moss in 2011, Kish was invited to navigate a maze of pillars set up in the bat laboratory. He stumbled several times against the obstacles as he found his way using tongue clicks. It appeared to Moss and her research team that blind humans produce less-detailed images than bats, and they suspected that other factors played a role in Kish’s echolocation.

“Aided by movement (active listening like bats), visually impaired humans like Kish may also use other senses like passive listening, vibration, and touch to help them navigate. Prior experience and learning also play a role in complementing echo processing. They can use spatial memory to record paths travelled for future navigation,” Moss explained.

Prof. Cynthia Moss and her research team at Johns Hopkins University.

There is certainly much to learn in terms of echolocation. The research findings on bats have inspired Moss to continue her investigation and develop sonar-type devices to improve navigation for the blind.

Perhaps now we will never look at these tiny, yet mighty, animals in the same way again.

Prof. Cynthia Moss

Prof. Moss obtained her BS with honors in Zoology from the University of Massachusetts, Amherst in 1979 and her PhD in Experimental Psychology from Brown University in 1986. She was a Postdoctoral Fellow at the University of Tübingen (1985-1987) and a Research Fellow at Brown University (1987-1989) before she accepted a faculty appointment at Harvard University in 1989. At Harvard, she received the Phi Beta Kappa Teaching Award (1992) and was named the Morris Kahn Associate Professor (1994). In 1995, she moved to the University of Maryland, where she was a Professor in the Department of Psychology and the Institute for Systems Research until 2014. She then joined Johns Hopkins University and is currently a Professor in the Departments of Psychological and Brain Sciences, Neuroscience and Mechanical Engineering.

Prof. Moss’s research combines behavioral, neurobiological and computational studies to investigate scene perception, spatial attention, navigation and memory. She and her laboratory members have established methods to collect multi-channel wireless neural recordings from free-flying bats, which allow the study of brain systems in animals engaged in natural behaviors.

She has edited two books, Neuroethological Studies of Cognitive and Perceptual Processes (1996) and Echolocation in Bats and Dolphins (2002) and has served as an Associate Editor of Behavioral Neuroscience, the Journal of the Acoustical Society of America, the Journal of the Acoustical Society of America Express Letters, and the Proceedings of the Royal Society, B.

Prof. Moss was elected as a Fellow of the Acoustical Society of America (ASA) in 2001, the American Association for the Advancement of Science in 2012, and the International Society for Neuroethology in 2018. She is also a member of the Society for Neuroscience and the Association for Research in Otolaryngology. The ASA awarded her the Gallery of Acoustics Multimedia Presentation Prize in 2011 and the William and Christine Hartmann Prize in Auditory Neuroscience in 2017. In 2018, she received the Christopher Clavius Award from Sigma Xi and the James McKeen Cattell Award from the Association for Psychological Science.

Having recently received a Humboldt Research Award, Moss will collaborate with colleagues at the University of Tübingen in Germany on research projects this spring and summer.

Photo: Will KIRK, Johns Hopkins University Office of Communications