While the majority of music psychology research has focused on music in a Western context, the field has expanded along with ethnomusicology to examine how the perception and practice of music differs between cultures.[10][11] It has also emerged into the public sphere. In recent years several bestselling popular science books have helped bring the field into public discussion, notably Daniel Levitin's This Is Your Brain On Music (2006) and The World in Six Songs (2008), Oliver Sacks' Musicophilia (2007), and Gary Marcus' Guitar Zero (2012). In addition, the controversial "Mozart effect" sparked lengthy debate among researchers, educators, politicians, and the public regarding the relationship between classical music listening, education, and intelligence.[12]