Gastro-trickery: how optical illusions could fool our minds and our taste buds

Sarah Knapton
An image of Picasso on the left, Jastrow's original image, and the 'Bistable bit'

When psychologist Joseph Jastrow created his whimsical duck/rabbit illusion in 1899 it was to prove that an individual’s perception of the world is based on their emotional state, background and surroundings.

A child with a beloved pet bunny, for example, or an adult looking forward to Easter would naturally see the rabbit, while the thoughts of a field sports enthusiast should spontaneously turn towards the duck.

But now chefs believe the same mind games could alter the taste of food and even persuade diners to choose more sustainable meats.

Jastrow's rabbit/duck illusion 

Oxford Universityand multisensory dining experts Kitchen Theory are currently midway through an experiment based on Jastrow’s rabbit illusion, attempting to see if they can alter the taste of food simply by encouraging the brain to switch between two states while eating.

The rabbit/duck illusion is known in scientific terms as a ‘bistable precept’ or an image made up of two realities, which forces the brain to choose just one picture at a time or switch between the two.

To test if such brain switching could also change the taste of food, Kitchen Theory’s chef Jozef Youssef, has created a dish called the ‘Jastrow Bistable Bite’ which is a mixture of rabbit and duck.

Jastrow's Bistable Bite with the rabbit/duck illusion painted in orange sauce  Credit: Prof Charles Spence/Kitchen Theory

A simplified version of Jastrow’s illusion is then piped onto the plate in blood orange sauce in the hope that the switch between the two will fundamentally alter the flavour.

If it works, it will be the first time that anyone has proven that taste can be altered simply by looking at an image.

Charles Spence, professor of experimental psychology at Oxford University who has helped Heston Blumethal create his culinary masterpieces, said: “It may take two to three seconds but we think people might start to notice a different taste in their mouth, based on the image they are looking at.

“We found that people tend to see one of the images more dominantly to begin with, but then there is the ‘aha’ moment where they suddenly see the other, and the brain starts to flip back and forth between the two, and it is that we are interested in.

“Rabbit is also something we should be eating more of, so if we can convince people to have a conversation about the taste, and give it a try to see if they like it, then it might alter their idea of it being an acceptable meat.

“Currently in Britain rabbits are viewed as pets whereas in Spain they are seen as everyday ingredients, so maybe we could change the perception in the UK because rabbit is a readily available source of protein which we should be using more.”

Professor Charles Spence Credit: Jeff Gilbert 

The team is also hopeful that the ‘aha’ moment of understanding the illusion will also stimulate the reward centre of the brain, flooding the body with happy hormones which, in turn, improves the taste.

Recently they created an ingenious dish in which the diner opposite could pick out the face of Picasso, again creating the ‘Eureka’ moment of discovery which boosts flavour and enjoyment.

Prof Spence added: “We know that illusions like this create a surge of happiness and pride when people finally see them, which triggers the brain’s reward mechanism and creates a more positive experience.

“It also stimulates laughter and conversation, and that kind of sociability at the table has been shown to improve taste perception.”

Can  you spot the face? The Picasso dish as it would appear to a dining partner  Credit: Kitchen Theory

In the first part of the experiment, which was published in the International Journal of Gastronomy and Food Science, the researchers asked nearly 1,000 people online to pick whether they thought the piped sauce in the ‘Jastrow Bistable Bite’ dish was a duck or a rabbit.

The aim was to select the most ambiguous positioning of the illusion for future taste tests. In coming weeks they intend to serve up the dish to diners to see if it really will alter flavour.

Previously Prof Spence has shown that flavour can change based on sounds, an effect known as ‘sonic seasoning.’

The team is also experimenting with playing the sound of duck shoots and the slaughter of animals while diners are eating to encourage people to take greater responsibility for where their food comes from.