Addiction (image) University of Texas at Austin Caption The rats in the study were isolated from their peers for about a month from 21 days of age. That period is comparable with early-to-middle adolescence in humans. Credit Creative Commons. Some rights reserved. See http://creativecommons.org/licenses/by-nc-sa/2.0/deed.en. By chandrika221. http://www.flickr.com/photos/14554939@N08/2357837491/ Usage Restrictions Image can be re-used under a Creative Commons license. There must be attribution. You may not use this work for commercial purposes. If you alter, transform, or build upon this work, you may distribute the resulting work only under the same or similar license to this one. 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.