A noted expert on the neuroscience of laughter has turned his focus to tears. Or more precisely, how digitally removing tears from photos of crying people makes it tough to tell just what emotion is being expressed.

For research recently published in the journal Evolutionary Psychology, Robert R. Provine, a professor of psychology at UMBC, gathered hundreds of slides of crying and non-crying people from photo sharing sites like Flickr. With some simple Photoshopping, tears were removed from the shots of crying people. The tear-free images and their teary counterparts were shuffled in with a long sequence of portraits of people with neutral expression and shown to undergraduate volunteers.

When asked to rate the emotions being expressed by the now-tearless faces, the results were startling: faces without tears not only don’t appear very sad, but are seen as displaying awe, concern, contemplation or puzzlement.

“Remarkably, the role of emotional tears as a visual signal has been neglected,” Provine said. “On one level, this confirms that tears signal sadness, but the surprise is that tears confer meaning to neutral faces. In other words, tears are a breakthrough in human emotional signaling.” Only humans produce emotional tears.

"Tears add meaning and nuance to the limited expressive range of the neuromuscular instrument of the human face. Like sobbing and laughing, tears are honest signals, and are hard to fake,” said Provine. “We need to replicate research on human facial expression using tears as a variable. They change everything”

Lacking Photoshop, you can approximate the effect of tear removal by using your finger to block out the tears in any photograph.

Provine’s research focuses on the neuroscience of everyday life, what he calls “sidewalk neuroscience.” He believes that common behaviors can provide startling insights into human nature and how the brain works.

Provine’s latest work on tears, yawning, laughter and many other fascinating but neglected human behaviors will be presented in a book to be published by Harvard University Press.