Most people don’t like to be told that we are stuck in old habits of thinking or that we are behind the times. We prefer to believe that we are sensible people who can adjust our thinking when the circumstances change. But in fact, we often have no idea how many outdated instructions we’re carrying around in our mental checklists.

Not long ago, my husband pointed out one of mine when he asked why I loaded the dishwasher a particular way. He had noticed that I didn’t put spoons next to other spoons in the basket. I explained that my mother had told me to do it like that, when loading the dishwasher was one of my chores as a child, because otherwise the spoons might nest together and not come clean. He replied that maybe this was a problem 40 years ago, but it wouldn’t happen with a good modern dishwasher.

After I thought about it for a moment, I realized he was correct. The spoons always came out just as clean when he was the one loading the dishwasher and put them next to each other. It simply hadn’t occurred to me that there might not be any real need to keep them separate.

I believe that most of our social prejudices have equally simple underpinnings. They’re based on things that were said long ago—that it was best to keep certain kinds of people separate, or to have different ways of treating them. Maybe some of those ideas made sense in their original context of a world with vastly different cultural expectations and more primitive technology. Maybe they never really made sense. But however it might have happened, they ended up as entries in society’s collective checklist of how things ought to be done.

Whether our antiquated notions have to do with the proper placement of the spoons in the dishwasher or of the people in our community, we feel uncomfortable when someone points out the flaws in our thinking. After all, we’ve always done things the same way without seeing any reason to change, so how can there be anything wrong? We’re reasonable people, and we certainly would have noticed if we had been doing something that made no sense—wouldn’t we?

Once we get past our initial feelings of denial and annoyance, though, we generally do acknowledge the facts in front of us. Although humans are creatures of habit on both a social and an individual level, we are capable of changing our ways, even if it might take a little while for new information to sink in.