Barbie, Oppenheimer, and the two conversations they opened.

Two films opened on the same weekend. One was the most commercially successful film of the year. The other was about the most destructive weapon in human history. My children wanted to see the first one. My husband wanted to see the second. We negotiated, as one does, and the outcome was that we saw Barbie on Saturday and Oppenheimer was watched at home later, in sections, with considerable pausing and explaining.

I'm a biologist, not a film critic. But I study how children process information, and Barbenheimer — the cultural phenomenon of these two films opening simultaneously — provided one of the more interesting case studies of the summer in terms of what different kinds of content do to children's conversations.

Barbie opened a conversation about gender, identity, and the gap between how things appear and what they actually are. My daughter, twelve, had opinions. Strong ones. The conversation lasted several days and wandered into territory — what it means to be a woman, what performance is, what authenticity is — that we had not navigated together before.

Oppenheimer opened a conversation about responsibility. My son, nine, asked: did Oppenheimer know the bomb would kill that many people? I said: he knew it would kill a great many people. He said: then why did he make it? And we were in a question that philosophers have been asking for eighty years, at the dinner table on a Tuesday evening.

The mechanism I'm describing is not specific to summer blockbusters. It works with news events, with books, with any shared cultural experience that creates a common reference point. The shared reference is the entry point — the thing that makes the conversation possible. Without it, the topic has to be introduced directly, and direct introduction is almost always less effective.

What interests me, as a biologist, is not the content of either conversation but the mechanism. Both conversations were opened by an external artefact — a film — that provided the shared reference and the emotional activation necessary for the conversation to begin. Without the film, we would not have had the conversation. The topic existed before the film; we just hadn't found a way in.

This is what cultural artefacts do at their best. They give families a shared point of entry into conversations that would otherwise require one of the adults to manufacture a reason to have them. Children resist directly initiated conversations about serious topics in a way they don't resist conversations that emerge from something they've already engaged with.

The research on this is consistent: children are more likely to discuss difficult topics if the discussion begins from a shared reference point — something seen, heard, or experienced together — than if the topic is introduced directly. The film is the Trojan horse. The conversation is what's inside it.

This is one of the reasons I think cultural participation matters for families. Not because Barbie is important, or because Oppenheimer is important, though both are. Because being part of the same cultural moment gives families a shared language for conversations that might otherwise not happen.

Both conversations are still ongoing. My daughter is still thinking about Barbie. My son is still thinking about Oppenheimer. These are, I would argue, exactly the right things to be thinking about at twelve and nine respectively.

The one thing I'd add to the observation about shared cultural artefacts: they need to be genuinely shared. The parent who watches the film and reports back to the child is not creating the same entry point as the parent who watches the film with the child. The watching-together is the mechanism. The Trojan horse needs to be inside the walls before it opens.

Both conversations — the Barbie one about gender and the Oppenheimer one about responsibility — were conversations I would have found difficult to initiate directly. Both were made possible by the film. I am not recommending these specific films to anyone. I am recommending the principle: watch things together with your children when you can, and pay attention to what comes out of the watching.

What film, book, or cultural event has opened a conversation in your family in the past year that you wouldn't have found another way into?

And: what conversation has been waiting for the right Trojan horse?

This week: choose one cultural artefact — film, book, exhibition, piece of music, anything — that you suspect might open a conversation you've been wanting to have. Watch it together. Ask one question afterwards that isn't about whether they liked it.

My son has subsequently looked up everything available about the Manhattan Project. He has opinions about J. Robert Oppenheimer that are, I think, more nuanced than mine at nine. Children who are allowed into difficult questions become people who can hold difficult questions. That seems worth the Tuesday evening.

Names of people and brands in these editions are changed. Whoever was there and reads this knows what we are talking about.