Researchers at Yale University have discovered that mammals have the ability to dream and make'visual sense' of the world before they've even opened their eyes for the first time. The new study looked at waves of activity in neonatal retinas of a group of mice that had not yet opened their eyes for the first time and found that they are'capable of pretty sophisticated behavior.' The retinal waves moved in a pattern similar to what would be seen if the animal was actually moving in a physical environment. 'This early dream-like activity makes evolutionary sense because it allows a mouse to anticipate what it will experience after opening its eyes, and be prepared to respond immediately to environmental threats,' the study's co-author Yale School of Medicine professor Michael Crair said in a statement. Yale researchers have discovered mammals dream before they've opened their eyes for the first time.