Are We the Only Ones That Posit Ends for Ourself?

We're the only kind of rational beings that can look at and evaluate this. So my dog might really want his treat, and if i hide it from him, he could still want his treats. He doesn't have he mental flexibility about his ends. Even if you attribute choice, there's not th kind of mental flexibility that we have. reason gives us this mental flexibility to posit ends for ourselves.