Our fascination with what makes us us has inspired decades of research. One popular idea is that our capacity for language sets us apart from other animals. More recent accounts have incorporated emerging insights from evolutionary and developmental psychology. For instance, in A Natural History of Human Thinking (Harvard University Press, 2014), Michael Tomasello argues that our ability to take on different perspectives makes us exceptional. Tomasello writes that as our environment pushed us to become more cooperative, humans had to adapt their behaviors accordingly. In doing so, we developed the ability to see the world from other points of view. Tomasello even asserts that language came out of this growing need to know the minds of others.
Another take on the question of what sets us apart comes from brain science. In The Making of the Mind: The Neuroscience of Human Nature (Prometheus, 2013), cognitive psychologist Ronald T. Kellogg takes the broad view, adopting the stance that a network of interacting traits, rather than a single ability, makes humans special. The key factors, Kellogg proposes, are our complex memory, capacity for language, social intelligence and relationship with time, which allows us to mentally travel into the past and future.
For readers less wrapped up in the question of us versus them, science writer Jennifer Ouellette's book on me versus you might appeal. Ouellette (who blogs for Scientific American) tackles why, in spite of sharing nearly identical genetic material, our personalities can diverge so widely. In Me, Myself, and Why: Searching for the Science of Self (Penguin Books, 2014), she explains why our genes do not necessarily define who we are or who we become. She embeds herself into the narrative, taking us on her journey as she gets her genome sequenced and her brain scanned. Ultimately delving into the science of ourselves will not yield firm conclusions about our identities. Rather we come closest to understanding who we are through the narratives we weave about our own lives.