For retired GP Judy Stokes, a Tuesday isn't just a day of the week – it's vividly yellow. And the entire sweep of human history, from 100,000 BC to the year 2500, exists as a vast, three-dimensional grid inside her mind.
A Lifelong Calendar in the Mind
Judy has spatial-sequence synaesthesia, a neurological condition where her brain blends senses and concepts. For her, units of time, numbers, and the alphabet are not abstract ideas but have specific shapes, colours, and positions in space. She only discovered there was a name for her unique perception in her 60s, after decades of assuming she was simply "very odd."
The revelation came while researching anxiety management for her young patients. She stumbled upon studies from Macquarie University in Sydney about grapheme-colour synaesthesia, where letters and numbers invoke specific colours. This led her to learn about spatial-sequence synaesthesia, which perfectly described her experience.
"If you say a date to me, that day appears in a grid diagram in my head," Judy explains. Public holidays and birthdays are already imprinted on this mental calendar. She can recall the birthdays of friends she hasn't seen for 65 years and picture her kindergarten classroom in minute detail.
Not Just Time, But a Map of Reality
Judy's synaesthesia extends beyond calendars. The alphabet and numbers follow distinct spatial patterns. This has gifted her with a formidable memory and an intuitive grasp of mathematics and money. "I don't need a calculator for basic arithmetic," she says, explaining that prices sit on a relative "number map" in her mind.
Her mental diagram is also immersive. When planning her day, she is physically within the grid in her imagination. An upcoming concert would see an image of the venue superimposed on the 7pm to 10pm slot for that particular date.
Professor Anina Rich, a cognitive neuroscientist and chair of the synaesthesia research group at Macquarie University, notes that an estimated 10% to 20% of people have some form of spatial-sequence synaesthesia, though manifestations differ. Some see time in circles or squares, while Judy's grid runs left to right, veering up and down.
From Secret Shame to Scientific Wonder
For most of her life, Judy kept her perceptions hidden. A casual remark to a friend about Tuesdays being yellow was met with such bafflement that, out of embarrassment, she never brought it up again. This silence lasted through a 30-year career in general practice.
Discovering she was not alone was liberating. She joined research projects, learning extensively about her own and others' experiences. While modern technology like phone diaries has reduced the practical advantage of her internal calendar, it still proves handy for trivia nights where historical or geographical dates are required.
"Sometimes I’d like to be more laissez-faire and less structured in my head but I do find it fascinating," Judy reflects. She is keen for science to learn more, even joking that neuro-researchers can have her brain one day. She expresses a desire to experience another person's perception, to "see what they see."
Her story highlights the astonishing diversity of human cognition. "We are all alike and yet our brains are surprisingly different," she says. "Long may that continue."
