Travelling by air can affect one's memory, shows a recent study conducted by Kwangwook Cho, researcher at the University of Bristol, UK . After conducting tests on 20 female flight attendants using the magnetic resonance imaging technique, Cho found that the right lobe of their brain was smaller than usual. The size, the study concluded is dependent on the period of rest that the crew gets before it has to fly again. There is also a correlation between reduction in the size of the brain and the high level of stress hormone called cortisol. The hormone may be the reason for the small size of the brain, ( Nature Neuroscience , Vol 4, p567