A person’s memory is a sea of images and other sensory impressions, facts and meanings, echoes of past feelings, and ingrained codes for how to behave—a diverse well of information.

Though we learn so much during our first years of life, we can't, as adults, remember specific events from that time.

But studying this phenomenon is challenging. “The hallmark of these types of memories, which we call episodic memories, is that you can describe them to others, but that’s off the table when ...