Catherine J. Mondloch, a professor of psychology and the director of the face perception lab at Brock University in Ontario, said, “If you think even about Halloween, one of the things we know about really young children, preschool age, is when the appearance of something changes, they think the thing itself has changed.”

For parents who are starting to wear masks, she said, “Put it on, put it off a few times, so the child sees it’s still daddy.”