Adventurous mice have bigger personalities.br br By observing the behaviors of grown up twin mice, researchers in Germany have determined that facing new challenges sparks growth in adult brains. br br Initially wanting to discover what shaped the distinct personalities of the duos, scientists set 40 twin mice loose in an activity-rich environment.br br What they found was that new experiences stimulated the growth of neurons in the hippocampus. The development of the new neurons depended upon how adventurous the mice were when engaging with their surroundings.br br The increased quantity of fresh transmitters was also found to make the mice more flexible in their reactions to new information. br br While all of that is clearly great news for mice, it’s also good news for people.br br The experiment’s principal researcher said, “Adult neurogenesis also occurs in the hippocampus of humans. Hence, we assume that we have tracked down a neurological foundation for individuality that also applies to humans.” br br So, what happens to the mice that don’t grab for the golden ring?br br A study performed a couple of years ago revealed that mice that take a passive response to challenges become increasingly docile when faced with stresses. br br After a time, many of them became completely inert when times got tough.