To look at how different measures of behavioural arousal interact with one another and whether there is an association between such measures and genes already known to influence arousal and attention.The study involves performing a simple computerized test of cognition and attention in which participants will be asked to identify particular target sounds presented through headphones. Participants will perform this task while we measure electrical activity of the brain using an electroencephalography (EEG) cap and also the size of the pupils using a small camera. For the genetic collection we will ask participants to provide a small saliva sample spitting into a small plastic cup.This session will take no longer than two hours to complete in total.