Because of our greater brain complexity, our emotions tend to be more nuanced and complex, more influenced by cognition and by our considerations of the past and the future. Animal emotions are simpler, more directly tied to actions and to the here and now. Dogs may growl at a stranger, rub against a beloved and trusted owner, or wag their tails at a sign that they are about to be taken for a walk. In contrast, human emotion is much less tied to the present. We regret the past and worry about the future. And our emotional responses are not restricted to our immediate environment. Human beings might become depressed after reading a newspaper article on global warming, worry about what their friends think of their lovers, or feel jealous of a high school friend’s success at work.