Philip Aston and Christine Gavin, in collaboration with Adam McNamara, Kaylee Moakes, and Annette Sterr in the Department of Psychology at Surrey, published the paper “The importance of the derivative in sex-hormone cycles: a reason why behavioural measures in sex-hormone studies are so mercurial” in PLOS ONE. Philip Aston met Adam McNamara (Psychology, Surrey) at a MILES Systems of Life Ideas Exchange. During this event, they agreed to work together on a joint project. Kaylee Moakes worked hard in collecting the experimental data from a lateralized spatial figural comparison task and this was analysed during a summer project by Chrissy Gavin (now a PhD student in Mathematics). The results showed that hormone concentrations alone cannot be used to predict the response times or accuracy rates. However, a model that involved hormone concentrations together with their derivative values gave much more accurate results. This finding suggests that there is a fundamental difference between the up-surge and decline of hormonal concentrations which may explain contradictory findings in earlier studies. The published article is available here.