A poster presented at MidBrains 2009, a regional undergraduate neuroscience conference at Macalester College, St. Paul, MN, May 2,2009 Higher activity in left frontal cortical regions is associated with experiences of pleasantness (Davidson, 2000). Participants listened to seven musical excerpts while EEG activity was continuously recorded. An original excerpt was selected and a musical search engine (Manaris et al, 2008) identified three similar excerpts and three dissimilar excerpts based on power-law metrics for melody and timbre. In response to each excerpt, participants (n = 1 9) rated their own activation and pleasantness, and their familiarity with and liking of the music. Asymmetry at frontal electrode pairs and pleasantness and liking ratings indicated different responses to similar than to dissimilar excerpts. All frontal electrode pairs (Fp2/Fp1 , AF4/AF3, F4/F3, F8/F7, FC2/FC1 , FC6/FC5) show significantly greater frontal asymmetry (lower alpha power on the left) for similar than for dissimilar excerpts; participants also rated similar excerpts as significantly more pleasant and better liked. Asymmetry and psychological rating differences were even more pronounced when comparing the most similar and the most dissimilar excerpts. Significant pleasantness and liking differences were also found between the original excerpt and dissimilar excerpts. These findings suggest a physiological basis for differences in psychological experience of pleasantness and validate the search engine as a tool to predict affective responses to music. This material is based upon work supported by the National Science Foundation under Grant No. 0849499 and No. 0736480 from the Division of Information and Intelligent Systems and Grant No. 051 1 082 from the Division of Undergraduate Education.