Tasting lemons when they see a number seven, regarding a certain letter as being yellow in color. Not a great deal is known about why some people experience an overlapping of the senses, a phenomena known as synesthesia. But a new study conducted at the University of Sussex has suggested that specific training of the mind can induce the effects of the condition. The study even suggests that such training can boost a person's IQ.

It is believed that around one in 23 people experience synesthesia. One of the big question marks surrounding the neurological condition is whether it is a result of our genes, or induced through behavior, such as the use of those colored magnetic letters found on fridges around the globe.

Psychologists at the University of Sussex's Sackler Center for Consciousness Science subjected a group of 14 adults to a nine week program designed to incite traits of synesthesia. They found that by the project's end, the participants had strong enough letter-to-color associations to pass standard testing for synesthesia. The majority also reported the letters themselves seeming "colored" and possessing certain personalities, such as "x" being boring and "w" being calm, for example.

Even more remarkably, the participants also experienced a boost in IQ by an average of 12 points, compared to a control group that wasn't subjected to the training.

"The cognitive boost, although provisional, may eventually lead to clinical cognitive training tools to support mental function in vulnerable groups, such as Attention Deficit Hyperactivity (ADHD) children, or adults starting to suffer from dementia,” says Dr Daniel Bor, one of the study's co-authors.

Though the findings suggest that synesthesia can be developed through behavior or training, the scientists say the two aren't mutually exclusive and this doesn't rule out the possibility that the condition has a genetic component.

“It should be emphasized that we are not claiming to have trained non-synesthetes to become genuine synesthetes," says Dr Nicolas Rothen, the study's other co-author. "When we retested our participants three months after training, they had largely lost the experience of seeing colors when thinking about the letters. But it does show that synesthesia is likely to have a major developmental component, starting for many people in childhood.”

The research was published in the journal Scientific Reports.