Weighty. Heavy. What do these words have to do with seriousness and importance? Why do we weigh our options, and why does your opinion carry more weight than mine? New research suggests that we can blame this on gravity. Heavy objects require more energy to move, and they can hurt us more if we move them clumsily. So we learn early on in life to think more and plan more when we’re dealing with heftier things. They require more cognitive effort as well as muscular effort.