Your brain can track two voices at the same time

You know the trick of picking one voice out of a crowded room — the "cocktail party" problem. A new study in PLOS Biology looks at the messier moment when you switch your attention from one talker to another, and finds the brain doesn't hand off cleanly: for a beat, it tracks both voices at once.

Researchers sat normal-hearing adults in an immersive mix of two competing speakers over a wash of background babble, recorded their brain activity with EEG, and cued them to switch focus every 15 to 30 seconds. Reading the neural signal, the team could tell which voice a listener was following — and saw the brain lock onto the new speaker before letting go of the old one, briefly encoding both streams together. The overlap lined up with a dip in "alpha" brainwaves, a marker of mental effort.

The team used large language models to model how listeners rebuild the thread of a conversation, and found signs that the brain resets its sense of context each time attention jumps to a new voice.

Previously:
• Researchers create AI headphones that let you hear a single person in noisy crowds
• I hear phantom music when I use a white noise machine, and I'm not alone