In 2020 Adolfo García, a neurolinguist at Argentina’s University of San Andrés, had a chance encounter with a photographer who amused his models by chattering to them backward—the Spanish word casa (house) became “asac,” for instance. Upon learning that the photographer had been fluent in “backward speech” since childhood and was capable of holding a conversation entirely in reverse, García set out to study the phenomenon.

His research on this amusing speaking style drew enough attention to garner him an Ig Nobel Prize, an award sponsored by Harvard University since 1991 for research that “first makes people laugh and then think.” Backward speech confers no practical advantage to its speakers. Perhaps it merely exists for the sheer enjoyment of the speaker and listener, who recognize the sounds in asac or “onom,” which is from the Spanish word mono (monkey). Nevertheless, this skill, which García says was initially dismissed by his acquaintances and colleagues as “ridiculous and useless,” is by no means a total waste because it offers insights into how the human brain processes language in atypical ways.

“We had the opportunity to explore something unusual, even, at times, absurd,” García says of the 2020 Scientific Reports study for which he and his team won the Ig Nobel. This recognition took him by surprise, especially considering that he did not continue to pursue this particular line of research after the study was published. His research now focuses on addressing language difficulties in autistic people and in people with ataxia, Parkinson’s disease or neurodegenerative disorders. But García remains an ardent advocate for making backward talk more than a linguistic oddity. He hopes, in fact, that his work will prove valuable in developing more effective therapies for language disorders.

Around the La Plata River estuary, which abuts the province of Buenos Aires and some parts of southern Uruguay, the language of word inversion belongs to a type of slang called lunfardo, which is the product of immigrant languages from the late 19th and early 20th centuries. This linguistic marvel uses only letters or syllables swapped from back to front. In lunfardo, the word vesre represents the Spanish word for “reverse”—revés—with its syllables pronounced backward.

There are still legions of passionate lunfardo speakers today. Thousands of exchanges turn up in ordinary conversation: feca (café, or coffee), choborra (borracho, or drunk) or rioba (barrio, or neighborhood). In Argentina and Uruguay these words are part of the culture. They often show up in tango lyrics but are sprinkled as single words into conversation by almost everyone, though not as continuous backward speech as demonstrated by the photographer encountered by García.

Backward speech can be practiced in any language that has a “transparent” grammar, meaning that phonemes—the distinct sound units of a language—have the same sound regardless of their position relative to other parts of a word, according to María José Torres Prioris, a researcher in the faculty of psychology at the University of Málaga in Spain and at the Biomedical Research Institute of Málaga, who co-authored the Scientific Reports study.

Word reversals are possible in languages such as Spanish, Basque or some Mayan languages, in which there is a direct one-to-one correspondence between letters and sounds. For instance, Spanish has five vowels, and each one has a distinct sound that remains consistent across all words. In contrast, English, considered an “opaque” language, has 12 different sounds for these same five vowels. In Spanish, the letter A has a consistent sound and is written the same way, while in English, it can produce varied sounds, as seen in words such as “back” (/æ/) or “far” (/ɑ/). In some cases, it may be heard without being explicitly written, such as in “cup” (/ʌ/). Torres Prioris acknowledges that people can speak backwards in English as well, but the speaker and listener can get confused between how a word is pronounced and how it is written. That confusion of sounds does not exist in Spanish.

Backward speaking is not confined to the La Plata River area. In France speaking backward is called verlan, a term that is the inversion of the syllables of l’envers, meaning “the inverse.” Verlan includes expressions such as cimer for merci (thank you) or jourbon for bonjour (hello). Something similar exists in Medellín, Colombia, where people carry on in parlache, and in Panama, which has slang called reversina.

Cultural adoration for backward speak perhaps reaches an apex in San Cristóbal de La Laguna, a city in Spain’s Canary Islands where residents are pushing for official recognition of backward speak. Here the tradition got started in the 1930s by a barber who spoke backward. Today those he influenced have asked the United Nations Educational, Scientific and Cultural Organization (UNESCO) to declare the practice an “intangible cultural heritage of humanity.” Some San Cristóbal residents have even quarreled with Spanish-language professors and authorities at the Canarian Language Academy who contend that this way of speaking equates to nothing more than a linguistic game.  

The Ig Nobel–winning researchers’ prize consisted of an out-of-circulation Zimbabwean banknote and a PDF that could be printed out and folded to form a miniature cola box. The backward speakers in their study possessed an “extraordinary ability” to quickly reverse words (even invented ones), sentences and texts. These individuals could rearrange sounds but preserve a word’s identity effortlessly, García and Torres Prioris’s team found. Instead of saying plata (money), for example, they said atalp. They reversed the letters in the word, not the syllables, and even maintained the appropriate accents. “It is a much more complex mechanism” than a silly game, Garcia emphasizes.

In the Scientific Reports study, the scientists designed various tasks to assess the participants’ ability to produce words backward and forward. The researchers measured accuracy and speed in rearranging phoneme sequences, and they obtained structural and functional magnetic resonance imaging recordings.

One of the study’s findings shows that the participants had an ability to instantly engage in word reversal that could not be explained by, say, having a superior working memory (the type of memory that allows people to briefly remember a telephone number, for example). Additionally, these individuals did not exhibit any other reversal skills, such as mirror writing, or writing in reverse.

Neuroimaging revealed that backward speakers had more gray matter volume and connections among neurons, not only in regions associated with phoneme processing (along what is called the dorsal pathway of the left hemisphere) but also in other brain areas involved in semantic processes, certain visual functions and cognitive control. Backward speech therefore brings into play cognitive mechanisms beyond classical language circuits.

Another intriguing aspect of the team’s findings, according to Torres Prioris, shows that the brain plasticity demonstrated by the study’s backward speakers enabled them to “accomplish the same task with different neural resources.”

María Castelló, an associate professor of research in integrative and computational neurosciences at Clemente Estable Biological Research Institute in Uruguay, who was not involved in this study, believes that it has opened “a window into the mechanisms of phonological coding”—the recording of written, orthographic information into a sound-based code. Specifically, it sheds light on “an area that has been little explored in neurolinguistics,” Castelló says.

“Neuroimaging studies have revealed that the specific brain regions involved can vary among individuals, underscoring the plasticity of the human brain in adapting to exceptional linguistic abilities,” she adds. The most significant contribution of this study, Castelló says, is that it offering insights that enhance understanding of the neural mechanisms involved in processing sounds and constructing words.

Backward speak may seem to some like an absurd indulgence that does nothing more than provoke laughter among friends in places such as San Cristóbal de La Laguna. But García and Torres Prioris argue that this research is relevant for a deeper understanding of neurological disorders that affect language. “I can’t say that this study has a direct clinical impact, but I do think it goes in that direction,” Torres Prioris says.

Since the publication of the team’s article, Torres Prioris has focused on studying characteristic symptoms of poststroke aphasia, which affects the ability to speak and results from injuries to the brain regions responsible for language. People with aphasia may exhibit linguistic errors such as the inversion, substitution, addition or subtraction of phonemes when communicating. In this context, the identification of neural circuits associated with backward speech is, in her view, “a step forward” for the development of noninvasive brain stimulation treatments for people with this condition. And in the future, she hopes to derive an effective therapy from the results of studying backward speech.

“When confronted with something seemingly ridiculous or absurd, it is quite easy to dismiss it as if scientific value lies in grandiose, revolutionary and transcendent matters,” García says. “A lesson from this study is that if we see something absurd, and we fail to find inspiration, we are not thinking deeply enough.”