Why animals compare the present with the past

Humans, like other animals, compare things. We care not only how well off we are, but whether we are better or worse off than others around us, or than we were last year. New research by scientists at the University of Bristol shows that such comparisons can give individuals an evolutionary advantage. According to standard theory, the best response to current circumstances should be unaffected by what has happened in the past. But the Bristol study unpredictable world it is important to be sensitive to past conditions. The research team, led by Professor John McNamara in Bristol's School of Mathematics , built a mathematical model to understand how animals should behave when they are uncertain about the pattern of environmental change. They found that when animals are used to rich conditions but then conditions suddenly worsen, they should work less hard than animals exposed to poor conditions all along.