A report in Proceedings of the Royal Society B described a study that showed fish can learn fear from role models. According to the study’s authors, environment can influence the social transmission of fear. The study showed how risk aversion can be learned. The researchers also suggest their study may shed light on how fear disorders such as post-traumatic stress disorder (PTSD) develop in humans, which research shows can be influenced by social environment. For example, PTSD symptoms can be acquired from friends or family who have suffered trauma.