A bizarre audio clip going viral online has left people questioning reality and the trust in their own senses.
Depending on how you hear it, the clip features either the words 'green needle' or 'brainstorm', in a strange voice altered by sound-effects.
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Other auditory mind tricks have gone viral online before, including a clip in 2018 that could either be heard as saying the word 'Laurel' or 'Yanny', according to Today.
UCL speech sciences Professor Valerie Hazan told The Telegraph: "The effect seems to work as follows: When you ‘think’ green needle you hear that word, but when you ‘think’ brainstorm, you hear the other."
TikTok user orangeshortsgang posted the clip of a Hooters waitress pointing to the two words as a voiceover plays the sound.
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Prof Hazan said: "Basically, you are priming your brain to expect acoustic patterns that match expected patterns for a particular word.
"When faced with an acoustic signal which is somewhat ambiguous because it is low-quality or noisy, your brain attempts a ‘best fit’ between what is heard and the expected word."
Listeners are not hearing the words 'green needle' or 'brainstorm' but their minds are accepting those words based on what they see because of the low quality audio.
The debate originates from a 2012 video review of toys from the popular TV show Ben 10 Alien Force.
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The review's producer told The Telegraph that after publishing the review some of his audience had been confused about one of the words a toy's speaker announced: 'brainstorm'.
Back in 2018 another clip with a similar mind trick left its listeners divided between the words 'Yanny' and 'Laurel' for the same reason.
After some consideration from the clip's audience, it became clear those who picked up lower frequencies of the sound heard 'Laurel' and those who perceived the higher frequencies heard 'Yanny'.
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Some people who heard the 'brainstorm/green needle' video even claimed to have heard 'Hooters' instead.
That may be because they read the word 'Hooters' on the waitress's outfit, instead of the words presented on screen, according to Prof Hazan's explanation.
One listener said it was possible to hear one or the other without looking at the screen at all and imagining the words in your head instead.
Charlie Metcalfe