This article is part of a series in which we speak to individuals who – due to a unique job, location or experience – share an insight they wish others could know.

What’s the one thing people should know? We’re all thinking differently about the same thing.

As a child, Constantina Makridakis, a 28-year-old jewellery designer from Greece, thought everyone could taste voices and names.

Her father’s name, Nicholas, tasted like caramel-coated chocolate, while her mother’s name, Maria, was pasta with prawns.

The tastes were usually pleasant; the name Paul, a rich chocolate liquor, was particularly delicious.

“I thought everyone had this ability,” she explained. “It seemed natural to me. We talk from our mouth, so it made sense [that] we also taste names and voices … it seemed connected to me, so I didn’t ask anyone about this.”

That was until one day in her late teens, when her sister, Amelia, whose name tasted sweet – often in the form of syrup or jam – told her about a documentary on synaesthesia.

After watching it, Makridakis realised she had a form of synaesthesia, a perceptual phenomenon in which sensory experience triggers another.

Music as colours

The experience of synaesthesia can vary significantly. For example, American singer-songwriter Billie Eilish experiences the names of days of the week as colours, numbers and shapes.

Hungarian composer Franz Liszt is also believed to have been a synesthete, experiencing musical notes as colours. In 1842, he is said to have confused musicians in the Weimar orchestra when he instructed them, “Gentlemen, a little bluer, if you please!”

Janina Neufeld, a researcher at the Centre of Neurodevelopmental Disorders at Karolinska Institutet (KIND) in Sweden, said that although it may seem surprising for non-synesthetes to hear about Makridakis’s experience, most of us can relate if we think about our own internal sensory associations.

“When we listen to music, most people can relate to the idea that sounds could be brighter, smaller or higher up in space … this is to some extent what a synesthete perceives,” she said.

It is estimated that 2 to 4 percent of the world’s population experiences some form of synaesthesia, although the true number may be higher, Neufeld said. Like Makridakis, many do not realise they have it – or that their experiences are unusual.

Neufeld herself experiences a form of spatial sequence synaesthesia, a milder variation that some people may have without realising. At KIND’s offices in Stockholm, she explained her version by closing her eyes and outlining a circle in the air with her finger, which she described as a full year.

On the circle, which she said exists in her “inner space” or mind, the year starts at the bottom of an undulating sphere, which she described as looking like a roller coaster track, and goes counterclockwise, with some months, such as December, longer than others.

Exploring the brain

How synaesthesia works on a neurological level is not yet fully understood, Neufeld explained.

One leading theory suggests that synesthetes may experience less “synaptic pruning” during childhood, a process in which neurons and synapses that are not needed are removed. For example, a child may strengthen the synapses related to a parent’s voice but prune those related to strangers, reinforcing useful connections and removing redundant ones.

The idea is that this pruning process is less extensive for people with synaesthesia, allowing extra cross‑sensory connections to remain. Neufeld, who has studied Makridakis’s case, said researchers have found strong evidence that sensory regions of people who experience synaesthesia exhibit more brain activation and increased interaction between different brain regions.

‘We see different things’

Makridakis said her synaesthesia can be over-stimulating at times. For example, if she is watching a film and an actor’s voice tastes like orange juice, she can find herself distracted by that sensory connection.

It can also lead to unhealthy temptations. The American accent tastes like Coca-Cola, which means when she is in the United States, she can find herself craving the sugary soft drink.

US President Donald Trump’s voice and name taste like melted cheddar cheese to Makridakis, while British actor Daniel Radcliffe, who played Harry Potter in the popular film series, tastes like chocolate milk, while US hip-hop star Eminem’s voice tastes like Cheetos.

Overall, though, Makridakis is fascinated by her perceptions and feels that if synaesthesia is studied more, it could lead to a deeper understanding of the human mind.

At times, she has flirted with the idea that synaesthesia could hold some spiritual meaning, especially since she can also experience a form in which a colour can shimmer around people. Her sister, for example, appears sometimes with a dark green halo around her.

If there is one thing non-synesthetes can learn from her experience, she said, it is that “we’re all thinking differently about the same thing”.

“We should always remember that everyone’s mind is completely different. We could say that the same colour is red; we could call it red, but we see different things,” she said.

Neufeld echoed this sentiment.

“Usually we think that everyone perceives the world similarly … we think sensory inputs are perceived the same, but synaesthesia shows there is more to the sensory experience; there are also a lot of internal associations and experiences that can be very rich,” she explained.

“Synaesthesia illustrates perfectly how differently we actually perceive the world.”

Other articles in the series: