THE ROUGH GUIDE TO PSYCHOLOGYis mental symbols, allowing us to represent events, real or imagined,
through art and language. Finally, Hauser points to our unique capacity
for abstract thought, granting us the ability to ponder the existence of
an afterlife, gods and concepts like justice. Whether these four distin-
guishing features of human thought will remain in place after another
decade of animal research remains to be seen.
Reports of animal feats never cease to fascinate people, especially
newspaper editors. However, there is a more serious side to showing
what animals are capable of and understanding what makes humans
unique. Comparative psychologists believe that identifying areas where
our abilities overlap with those of other animals, and those where
our abilities have diverged, can help us to understand the evolution
of mental mechanisms. Consider the demonstration by Daniel Weiss
at Pennsylvania State University, which showed that, like humans but
unlike some other primates, Tamarin monkeys form an anticipatory
thumb-down grip shape when reaching for an upside-down glass.
Because Tamarins don’t use tools in the wild, this finding contributes to
the hypothesis that anticipatory motor planning is a necessary but not a
sufficient skill for the development of primate tool-use. Studies like this
help to reveal the evolutionary roots of our mental abilities, and from
there we can begin to uncover how genes came to build the brains that
made us human.