To see how well my first memory held up, I called my dad to verify the details. I was worried I had invented the detail of my mom’s parents being there, but he confirmed they had flown over from England for the occasion. He said my brother was born in the early evening, not at night, but considering the U.S. Naval Observatory says sunset in Highland Park that day was at 4:31 p.m., we could both be right. He confirmed my brother’s cot and the television, but he disputed one vital detail, phrasing it with the wary precision of a former doctor: “I won’t say with any confidence that Thomas the Tank Engine was on the TV.” Still, we agreed that if there was anything about the day that a 3-year-old would be more likely to remember than the father of a newborn son, it would be that.

The randomness of that detail makes me think it’s more plausible, if only because it would be such a bizarre thing to add in years after the fact. False memories do exist, but their construction appears to begin much later in life. A study by Peterson presented young children with fictitious events to see if they could be misled into remembering these non-existent events, yet the children almost universally avoided the bait. As for why older children and adults begin to fill in gaps in their memories with invented details, she pointed out that memory is a fundamentally constructive activity: We use it to build understanding of the world, and that sometimes requires more complete narratives than our memories can recall by themselves.

And, as people get older, it becomes easier to conflate actual memories with other stimuli. Reznick told me of a distinct memory he has of riding in a toy wagon and tractor with his sister. The problem is that he doesn’t so much remember doing it as he remembers seeing himself do it, and he discovered why when he came across an old photograph of him and his sister riding in that very same wagon and tractor on the sidewalk outside their childhood house. He had forgotten having seen the photograph before but had remembered what it depicted, and the latter over time became its own memory.

As he spoke, I thought of my only memory that might predate my brother’s birth. There’s a vague image in my head of my pint-sized self sitting between my parents on the plane ride to America. My dad confirmed the scant details I could provide were accurate, but the problem is one of vantage point. This isn’t a first-person memory like my trip to Highland Park Hospital, but rather a mental snapshot taken—or, more likely, constructed—of the three of us from the perspective of the plane aisle. Besides, a crucial detail is wrong: My “memory” forgets the fact that my mom would have been four months pregnant at the time. My dad assured me she was already showing by then, even if my mom would have strenuously denied that if asked. Perhaps my memory was just being exceedingly polite.