In The Devil's Dictionary, Ambrose Bierce describes the mind as "a mysterious form of matter secreted by the brain," engaged in a futile attempt to understand itself "with nothing but itself to know itself with."
Questions about the limits of self-understanding have persisted long after Bierce's 1911 publication. One user on Quora asks: "Is the human brain intelligent enough to fully understand itself?" A satirical headline at The Onion reports that psychology has come to a halt as "weary researchers say the mind cannot possibly study itself."
Despite such doubts, the science of the mind has made enormous advances over the last century. Yet many questions remain, along with the more foundational worry that motivated Bierce. Are there fundamental limits to what science can explain about the human mind? Can science truly explain consciousness and love, morality and religious belief? And why do topics like these seem especially ineffable — further beyond the scope of scientific explanation than more mundane psychological phenomena, such as forgetting a name or recognizing a face?
Psychology PhD student Sara Gottlieb and I decided to find out. In a series of studies forthcoming in the journal Psychological Science, we asked hundreds of participants to tell us whether they thought it was possible for science to one day fully explain various aspects of the human mind, from depth perception and memory loss to spirituality and romantic love.
We found that, on average, people judged some mental phenomena — such as depression and the ability to discern temperature through touch — much more amenable to scientific explanation than others — such as feeling pride or experiencing love at first sight.
Our next question was "Why?" What differentiates the phenomena believed to fall within the scope of science (such as visual perception) from those that fall beyond it (such as love)?
One hypothesis is that mental phenomena vary in how complex we believe them to be. Perhaps phenomena like love and spirituality are thought to be more complex than phenomena like depression or depth perception, and it's this complexity that leads people to judge some mental phenomena beyond the scope of scientific explanation. We tested this hypothesis and found no support for it. People did think that some phenomena were more complex than others, but these judgments didn't predict whether or not they thought a given phenomenon could be explained by science.
Fortunately, we also identified a host of characteristics that did predict whether or not a phenomenon was perceived to fall beyond the scope of science. We found that people were more likely to think that a phenomenon could not possibly receive a full scientific explanation if they thought the phenomenon involved an internal experience accessible through introspection, contributed to making humans exceptional, and could be controlled through conscious will. Thus more perceptual phenomena that we share with other species were typically judged to support full scientific explanations, while phenomena related to religion, morality, and more subtle emotions tended to be judged beyond the scope of scientific explanation.
For some of these phenomena, the very idea of a complete scientific explanation was accompanied by discomfort or unease. We asked our participants to tell us, for each phenomenon, whether the idea that science could one day fully explain it made them uncomfortable. On average, participants were pretty comfortable with the idea that science could fully explain phenomena like depression, headaches, and the ability to discern temperature through touch. They were less comfortable with the idea that science could one day fully explain falling in love or feeling transformed by a spiritual event.
Importantly, these findings don't tell us about what science can and can't explain. They tell us about people's beliefs about what science can and can't explain. But the implications are pretty intriguing. People don't seem to regard the complexity of a natural phenomenon as a critical barrier to scientific progress. Instead, those phenomena that involve the unique characteristics of the reflective mind — such as introspection and conscious will — are the ones that are taken to present a real obstacle for science. And those that contribute to making us exceptional — more than a "mere" animal among many — seem to place us further beyond what science can explain.
So what do people think explains the human mind, if not science?
Is an understanding of the human mind to be found outside of science — in poetry and in religion, in the arts and in action? Or is the mind fundamentally ineffable, the quest for understanding just as futile as Bierce warned? Whatever the answer, we'll have to use our minds to find out.
Tania Lombrozo is a psychology professor at the University of California, Berkeley. She writes about psychology, cognitive science and philosophy, with occasional forays into parenting and veganism. You can keep up with more of what she is thinking on Twitter: @TaniaLombrozo