From http://www.eurekalert.org/pub_releases/2012-02/sp-crs022012.php
[quote][R]esearchers writing in Therapeutic Advances in Psychopharmacology, published by SAGE, have shown for the first time that blood levels of a rosemary oil component correlate with improved cognitive performance
The investigators tested cognitive performance and mood in a cohort of 20 subjects, who were exposed to varying levels of the rosemary aroma. Using blood samples to detect the amount of 1,8-cineole participants had absorbed, the researchers applied speed and accuracy tests, and mood assessments, to judge the rosemary oil’s affects.
Results indicate for the first time in human subjects that concentration of 1,8-cineole in the blood is related to an individual’s cognitive performance – with higher concentrations resulting in improved performance. Both speed and accuracy were improved, suggesting that the relationship is not describing a speed–accuracy trade off.[/quote]