In the first part of the study, which looked at a group of more than 50 college students, participants were asked to complete different motor tasks with the study leader’s cell phone visible. In the second, participants completed motor tasks with their own cell phones visible. Performance on complex tasks suffered in both conditions when compared to control groups with no visible cell phone.

The sight of a cell phone reminds people of the “broader social community” they can access via texting and the internet, says study author Bill Thornton.

“With the presence of the phone, you’re wondering what those people are doing,” says Thornton, a University of Southern Maine professor. “Even if it’s just mental, your focus is not on the task at hand, whether it be trying to write an article, get this spreadsheet set up, or just socializing; your mind is elsewhere.”