Photo: Jacquie Boyd/Ikon Images/Corbis

Naomi Jacobs went to bed on a spring night in 2008 as a 32-year-old mother of an 11-year-old boy and a student at Manchester Metropolitan University. The next morning, she says, it was as if the last decade and a half of her life had never happened. In an interview with the BBC today, Jacobs says she woke up believing she was 15 years old.

She didn’t recognize her home or her son, and even her own voice sounded unfamiliar to her, much lower than she thought it should be. The 2008 technology throughout her house, including her smartphone and TV, looked to her like something out of a sci-fi movie. The best and only way to deal with the confusion seemed to be to go back to bed, as it often is. “I was convinced I was going to fall asleep … and wake back up in 1992,” she told the BBC, in a conversation about the book she’s written about the experience, Forgotten Girl. And yet she hadn’t forgotten everything: She could still remember things like phone numbers and her debit card PIN, and she even remembered how to drive, something she certainly didn’t know how to do at 15.

What she’s describing fits the description of dissociative amnesia, psychologist and Science of Us occasional contributor Christian Jarrett pointed out in a tweet this morning. Dissociative amnesia is a form of memory loss in which certain personal information is blocked out, though the person retains motor memory (like driving a car) and memory for things like facts and dates (like Jacobs’s PIN). Stress is said to trigger this type of memory loss, and the memories usually resurface in time.

In this way, Jacobs’s experience was typical of other recorded dissociative amnesia cases, in that her memories vanished after a period of illness and personal stress, and returned about six weeks later. Now that it’s behind her, Jacobs told the BBC she feels fortunate for the chance to see her adult life from a new perspective. It’s a weird thought exercise: What would 15-year-old you think of your life?