As I understand it the Mozart effect originally was reported in a 1993
letter to the editor of _Nature_, which described an experimental study
showing that listening to Perahia and Lupu's rendition of Mozart's Sonata
for Two Pianos in D, boosted the listeners' performance on a test of
spatial reasoning relative to control groups that either listened to a
relaxation tape or received silence.

The principal researcher, Francis Rauscher, has an interesting background
and is also involved in other promising work involving music and
psychology.  She has a web page:

   http://www.uwosh.edu/departments/psychology/biofrr.htm

Efforts to replicate and extend the original findings have been mixed.  The
following is a reference to an informative student paper in pdf format that
summarizes the original research, media reactions, and subsequent research
findings:

   http://www.stanford.edu/~lswartz/acad/mozarteffect.pdf

Lyle K. Grant | Professor | Centre for Psychology, Athabasca University,
1 University Drive, Athabasca AB, Canada T9S 3A3 | Ph: (780) 675-6236
Fax: (780) 675-6186 | http://psych.athabascau.ca/html/lyle/lgrant.shtml