Children who take music lessons before the age of six tend to be more intelligent than their peers, according to the results of a study in Canada.

Academics at the University of Toronto found that the IQ scores of six-year-olds who had taken keyboard or voice lessons were, on average, three points higher than normal. The study appears to support the Mozart Effect - a theory established in 1994 which claimed that listening to Mozart temporarily increases problem solving abilities. Professor Glenn Schellenberg, of the psychology department at the University of Toronto, who led the research, said: "It was a response to all the brouhaha about whether or not music makes you smarter."

In the latest study, children were recruited via a newspaper advertisement and divided into four groups. One group received free weekly keyboard lessons and another received free weekly singing lessons, at Canada's Royal Conservatory of Music. The third group was sent to free weekly drama classes, and the remaining group received no lessons at all. Before the experiment began, every child underwent a three-hour IQ test. A second test nine months later showed, as the team expected, that the IQ scores in all four groups had increased by at least 4.3 points. The children who had taken keyboard or voice lessons, however, scored on average, 2.7 points more than those who had taken drama lessons and no lessons. Professor Schellenberg attributed the latest results to the skills students needed to acquire in order to learn music. He said: "There are so many different facets involved, such as memorising, expressing emotion, learning about musical intervals and chords."

The possibility of an association between music and intelligence has interested scientists in recent years. Previous studies have linked musical aptitude to literacy and music lessons to mathematics achievement.

Last year, Hong Kong scientists claimed that children who took music lessons possessed superior verbal memory skills - the ability to remember spoken words. Other scientists have suggested that children who attend music lessons may have higher IQ scores because they tend to come from families that are better educated and wealthier than those of their peers.

This latest study is the first to feature a large number of children selected at random from a range of backgrounds.

The phenomenon was identified by researchers who assessed the ability of test subjects to complete four-dimensional puzzles. They discovered that the highest scores were achieved by people who had listened to Mozart before tackling the puzzles. The effect has since been attributed to Mozart's stimulation of mood.

Yesterday, the findings were supported by Melissa Sayer, the mother of five-year-old Molly, from London: "Molly has been taking piano lessons for one year - and she is top of her class at school. At the end of the year she won a prize for her academic achievement, for reading and maths. I hadn't made the association before, but it does make sense now that I think about it."