The study was unique in that the researchers also tested if participants could recall specific sights or sounds, known as implicit learning. They placed headphones on the patients during resuscitation and played three words — apple, pear, banana — and also used a tablet to display 10 images.

When asked if they remembered these, only one of the 28 patients who were interviewed correctly remembered the three-word sequence and none could recall the images. The research team also analyzed the recalled memories of 126 other cardiac arrest survivors who sent their experiences by mail or were in a community database.