ADHD (IMAGE) University of Barcelona Caption According to the study, some features like hyperactivity or impulsiveness could have been favourably selected for survival in ancestral environments dominated by a nomad lifestyle. Credit Paula Esteller (CNAG-CRG / IBE, CSIC-UPF) Usage Restrictions The image may only be used with appropriate caption or credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.