It’s a small but subtle change from the old version, and one that’s led me more than a few times to go back to my inbox instead of sending an email. Or think about every time Twitter changes its design, or Facebook moves things around in your news feed — where did Events go? — or when your favorite website redesigns its homepage and you “can’t find anything” anymore.

According to a new study in the journal Cognitive, Affective, & Behavioral Neuroscience by Jason Moser, Hans Schroder and others at Michigan State, that’s because our brains have a finite capacity for processing information — and when rules, or designs, change, we mess up. It doesn’t matter, it seems, if the new rules of a design are intended to make things easier for us — our brains will still have trouble processing the change no matter what. Which is why you see people getting so agitated when new versions of an OS move their trash can.

The study authors focused on one area of the brain, the anterior singular cortex, which is responsible for monitoring our actions — like which mouse button to press. “When you switch the rules on people, this part of the brain has to go into overdrive to suppress the old rule and remind itself that this is the new rule,” says Moser. “The cost of that part of the brain going into overdrive is it pays less attention.”