Scientists have found that personality can shift as animals age, and some species really do become less social, less curious and more irritable over time. Part of this comes from changes in the brain and nervous system as animals get older. Aging can affect dopamine and other neurotransmitters involved in motivation, reward and exploration, while declining energy levels can make animals less interested in play or unfamiliar situations. Older animals also tend to become more routine-focused and less tolerant of stress, which can make them seem noticeably “grumpier” than they were when they were young. So the grumpy old cat stereotype actually has some science behind it. 🐱