The science of speaking backwards

Sounds are not letters

Speech is a stream of sounds, called phonemes, and each one changes shape depending on its neighbours. When a recording is reversed, every sound is reversed too, not just their order. Gliding vowels flip: "eye" becomes something like "yah". A t at the end of a word moved to the front gains a puff of air. That is why reading a word backwards letter by letter almost never produces the right sound, and why the reliable method is to listen to the reversed audio and copy it.

Why your brain hears words in reversed speech

Reversed speech keeps the voice, the pitch and the rhythm of speech, so your brain treats it as language and tries to decode it. It finds near-words in the noise, which is called pareidolia. A study at Monash University found that listeners did not hear the "hidden messages" claimed by reverse speech promoters unless they were told what to listen for.

Speech is also surprisingly robust. In a 1999 study in Nature, Kourosh Saberi and David Perrott showed that a sentence stays understandable even when it is cut into very short pieces and each piece is played backwards.

People who speak backwards fluently

A few people can reverse speech on the fly, and scientists have studied them.

• A Serbian family (2016). A father and his daughter could speak backwards at will, an ability they had since childhood. Researchers found the daughter had an exceptional verbal working memory and identified rare gene variants shared by the two, as candidates for further study.
• Argentina and Spain (2020). A team led by Adolfo García and María José Torres-Prioris scanned two expert backwards speakers. Their skill was not explained by better working memory. Their brains showed more grey matter and connections along the left dorsal pathway, which handles speech sounds.
• The Ig Nobel Prize (2023). The second study won the Ig Nobel Prize for Communication.

The researchers noted that reversing is easier in languages where letters match sounds, like Spanish. English has far more vowel sounds than vowel letters, which makes it one of the hardest languages to speak backwards.

What this means if you want to learn

You don't need special genes for short phrases. Record the line, play it backwards slowly, copy it in chunks of two or three seconds and test yourself by reversing your try. That is the loop the science points to, and it is exactly what Revocal's Training does.

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