Listening Only Improves Lie Detection Accuracy to 61.7%, Research Shows

Closing your eyes when listening to someone speak can double your ability to detect deception, research suggests.

Simply shutting your eyes improves lie detection accuracy significantly, according to studies.

The human voice shifts instantly under stress. Adrenaline triggers fight-or-flight responses that tighten laryngeal muscles, producing a high-pitched and wobbly tone. Conversely, speaking to a loved one softens and deepens the voice.

When someone lies, the rhythm and intonation of their speech alter, and people are nearly twice as effective at spotting that distortion when they only hear – not see – the speaker.

Holly Watt, author of “The Good Listener,” volunteered as a Samaritan at university. After initial training, she spent hundreds of hours listening to callers discuss topics ranging from unreciprocated crushes to financial crises to bereavement. The listening role proved vital, but Watt grew increasingly fascinated by voices and how humans process vocal information.

Humans are remarkably adept at deducing information from just a few words, partly because physique shapes many voice characteristics. “Voices are an instrument and they reflect our physical nature,” said Prof Sophie Scott, director of the Institute of Cognitive Neuroscience at University College London. “If you think about a ukulele, a guitar and a violin, their sound is defined by the material they are made out of, the number of strings and how you play them. The voice is the same.”

People can gauge height because taller individuals have longer vocal tracts, producing lower resonances. Men’s voices are typically an octave lower than women’s. As people age, laryngeal cartilage may harden, making voices hoarser or weaker. Interestingly, women’s voices may lower with age while men’s may rise. Research indicates women’s voices become higher around ovulation due to estrogen’s effect on the larynx.

Much of this information is received subconsciously. “We’re very good at telling if someone is ill from their voice, for example,” Scott said. “The vocal folds get inflamed and vibrate differently.”

Listeners also infer geographic origin through accent and assess socioeconomic status, Scott noted, though these voice aspects can change. Vocal fry – the low-frequency “whateverrrr” style – may hint at media consumption. Even the late Queen’s voice shifted over her lifetime. “Voices are aspirational,” Scott said. “We had a charismatic senior person working here and everyone suddenly started talking like her. You change your voice depending on who you’re talking to.”

Watt attended a French school until age 13 and can immediately identify native French speakers. Different languages engage distinct facial muscles, altering jaw, cheek, and tongue movements. French speakers do not use upper cheek muscles like English speakers, a trait discernible even with a perfect English accent. Watt’s father, from near Glasgow, could identify a speaker’s specific Scottish town, and occasionally the street they grew up on.

Accents used to shift every 25 miles across the UK, but distinctions have softened. Scott cautioned against placing too much weight on accent: “People project a lot on to voices. Your reaction will often tell you more about your bias than about the other person.”

Voice evaluations occur within 200 milliseconds, said Prof Silke Paulmann, executive dean of the Faculty of Science and Health at the University of Essex. “Before we’ve fully processed the words or meaning, the brain has already started [analysis]. A wide variety of studies have shown that listeners pick up cues about emotions, motivations, engagement or attitude. I call this the ‘social intention’ of the speaker. Within an eyeblink, we can hear if someone is warm or cold, calm or stressed, positive or negative.”

These characteristics have evolved over millions of years. Speaking and listening – key elements in the transition from ape to Homo sapiens – are enormously complex. As listening evolved from a defensive mechanism for detecting danger to a communication tool with complex language, vocal structures, ears, and brains all adapted.

The process likely began around 27 million years ago when ancestors started distinguishing vowel sounds. Progress was slow. Humans retain auricular muscles – allowing ear movement seen in cats and dogs – but lost the ability to swivel ears about 25 million years ago. The hyoid bone in the throat, crucial for sophisticated vocalizations, appeared only about half a million years ago.

Evolution also made humans less effective at identifying liars. Dora Giorgianni at the University of Portsmouth’s International Centre for Research discovered that people are better at detecting lies when they only hear the speaker. This is because humans have limited information-processing capacity; attention and memory become overloaded when following audio and visual information simultaneously. Watt found that as a Samaritan listener, she read callers better over the phone because all attention focused on the voice alone, a finding consistent with Giorgianni’s analysis.

In Giorgianni’s experiments, some participants watched a video with audio of a mock suspect interview while others only listened to the audio. “Participants who only listened to the audio achieved substantially higher overall accuracy [in assessing lies] – 61.7% – than those who watched the video with sound – 35%,” Giorgianni said. “When too much information is presented at once – for example, visual details, facial expressions, body movements, tone of voice and the actual content of what is being said – the cognitive system must continually select what to focus on and what to ignore, which increases the risk of making inaccurate judgments.”

Other research by the University of Portsmouth during the pandemic concluded that wearing face masks improved juries’ ability to differentiate truth from lies. “From an intuitive or evolutionary perspective, one might assume that seeing facial expressions, gestures and posture should help humans detect deception,” Giorgianni said. “However, modern investigative settings differ from ancestral environments. The cues that matter for survival are not the same as those that distinguish a practised liar from a truthful witness in an investigative interview.”

Commonly taught clues – faster speech, rising pitch – appear in some individuals but not others, and also indicate stress that can occur without lying. “There is no single verbal cue that ‘gives away’ lying in a strong or reliable way,” Giorgianni said. “Common beliefs about nonverbal indicators of deception are frequently inaccurate and a clear, reliable ‘Pinocchio’s nose’ simply does not exist.”

Novelist Harriet Tyce, a recent contestant on “The Traitors,” noted the challenge. “What’s most surprising about the difficulties of spotting a liar on The Traitors is that one goes into it knowing that everyone could be – and in fact pretty much is – lying about something, which means that it should in theory be almost impossible not to spot it,” Tyce said. “But I think we are hardwired as humans to trust, and trying to override that instinct is nearly impossible.”

Several companies market AI-driven analyses that track voice, facial muscle movements, eye movement, and brain activity to identify lying. Dr Frederika Holmes, a consultant specializing in forensic analysis of speech and language samples, said limitations remain.

“Voices aren’t like DNA, which doesn’t change over the course of your life and can be directly compared from one sample to the next,” Holmes said. “Voices are plastic and they change depending on circumstances, so we can’t say with absolute certainty. We assess the points of similarity and difference and reach a conclusion regarding the strength of the evidence.”

Close listening can reveal some secrets of a voice, but not everything.

“The Good Listener” by Holly Watt is published by Raven Books (£18.99). To support the Guardian, buy a copy at guardianbookshop.com. Delivery charges may apply.

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