The researchers add that their results will be welcomed by teachers and parents who feel that music should be part of the pre-school and primary school curriculum.
The findings, which are backed by brain scans, are published today in the journal Brain by McMaster University's Institute for Music and the Mind in Hamilton, Ontario, and the Rotman Research Institute of the University of Toronto.
"While the greater improvement that we found in musical tasks is not surprising after one year of music lessons, greater improvement on a non-musical memory task in children taking music lessons is very interesting," said Prof Laurel Trainor, of the McMaster Institute "Furthermore, our research shows that this occurs in children as young as four years of age."
Prof Trainor, who led the study with Takako Fujioka, compared 12 children aged four to six years over the course of a year: six of the children (five boys, one girl) had just started a Suzuki music school; the other six (four boys, two girls) had no music lessons outside school.
The researchers chose the Suzuki method to ensure the children were all trained in the same way, were not selected according to their initial musical talent, and had similar family support.