On Sept. 1, 1999, Princeton University researchers reported that they had genetically modified mice to have improved learning and memory. Neurobiologist Joe Tsien, with collaborators at MIT and Washington University, found that adding a single gene to mice significantly boosted the animals’ ability to solve maze tasks, learn from objects and sounds in their environment and to retain that knowledge.

This strain of mice, named Doogie, also retained into adulthood certain brain features of juvenile mice, which, like young humans, are widely believed to be better than adults at grasping large amounts of new information.