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9. De Moraes, C. M., Lewis, W. J., Paré, P. W., Alborn, H. T. & Tumlinson, J. H. Nature 393, 570–573 (1998). 10.Du, Y. et al. J. Chem. Ecol. 22, 1591–1606 (1996). single person’s IQ-test performance (assuming a test reliability of 0.95, the 50% confidence interval would be 4.5 IQ points wide). To account for the Mozart effect, Rauscher’s group appealed to a model of cortical computation whose operations at the columnar level are compatible with qualities presumed to be present in Mozart’s music and with the cognitive processing presumed to be involved in spatial–temporal tasks. But any improvement in performance with music can also be explained by the fact that the complex visual transformation processes involved in three-dimensional mental rotation and similar difficult spatial tasks (such as paper folding and cutting) are associated with function of the right cerebral hemisphere, as is cognitive arousal. In support of this, one study found that listening either to Mozart or to a passage from a Stephen King story enhanced subjects’ performance in paper folding and cutting, but only for those who enjoyed what they heard. Another experiment found that 8,120 British schoolchildren performed better in response to (presumably enjoyable) popular music than to Mozart’s music, relative to a control group that heard a discussion of scientific experiments. Mozart’s effect on mood has been verified in standard questionnaires. In a metaanalysis of eight comparisons (with 201 subjects) of auditory relaxation instructions with Mozart’s music (Table 1, bottom), the music effect appears to be larger: d40.20 overall, and d40.56 for spatial– temporal processing. But as relaxation instructions aim to reduce arousal, it is not surprising that they should impair subsequent cognitive performance, especially on tasks that depend on the right hemisphere. I conclude that a shared right-hemisphere locus provides a plausible explanation for an intermittent, small positive ‘enjoyment arousal’ effect of Mozart’s music on difficult spatial tasks. It also explains the failure to find an effect from other stimulation, which may not be sufficiently enjoyable or arousing to subjects, scientific correspondence