Something that all synaesthetes have in common is that particular tones or words will always elicit precisely the same colours or tastes.
Psychology experiment shapes
Which one of these shapes is 'bouba' and which one is 'kiki'?
And Professor Spence thinks he can use this to enhance our experience of flavour.
The concept of sharp- and soft-sounding words was introduced in 1929, when Estonian psychologist Wolfgang Kohler designed an experiment that asked people to choose which of two shapes was named "bouba" and which was "kiki".
The vast majority of people choose kiki for the orange angular shape and bouba for the purple rounded shape.
Professor Spence thinks this strange language can influence our taste buds.
Working with world-renowned chef Heston Blumenthal, he is trying to directly combine an auditory experience into a dish.
"We've been giving people dishes and asking them questions about them, including is that food more of a 'bouba' or a 'kiki'? Or is it a 'maluma' or 'takete'?" he told.
Brie and cranberries
Brie is "very maluma" whereas cranberries are "very takete"
He said that two of the best examples are brie, which is "very maluma", whereas cranberries are "very takete".
"The idea is that you get people to take part in the experiment by giving them two plates of food, and saying 'one of these is a takete and one is a maluma,' but not tell them which is which until they've eaten it.
The team may also, he says, make up a few new tasty-sounding words for dishes at Mr Blumenthal's restaurant. "We haven't decided which ones to use yet."