Early concepts of intimacy: Young humans use saliva sharing to infer close relationships [video]
January 20, 2022
January 20, 2022
All Captioned Videos Publication Releases
CBMM researchers and authors, MIT/Harvard postdoc Ashley Thomas and MIT Prof. Rebecca Saxe discuss their newly released paper published in Science.
[MUSIC PLAYING] ASHLEY THOMAS: My name is Ashley Thomas, and I'm a Postdoc in the Saxe Lab at MIT and the Spelke Lab at Harvard. I study how infants recognize different types of social relationships, and how they learn about their specific social worlds, how they place themselves into relationships and into larger social groups.
In developmental psychology, there hasn't been a ton of work that asks how infants understand different types of relationships. There's been lots of work asking how they understand traits like being nice, or being mean. And there's other work that asks how they understand large macro groups, so whether you're in the same social group, but less about social relationships.
Whereas in other fields, such as anthropology or sociology, there's been a lot of work asking how people think about the family, how people think about close versus other types of cooperative relationships. And so we wanted to kind of marry these two fields together and ask whether infants recognize that cooperative relationships can either be intimate or more casual.
REBECCA SAXE: One hypothesis that anthropologists suggested is here's a cue, something you could see in your environment that would tell you who's really close to whom. Imagine you go out for a milkshake with somebody. So you could each get your own milkshake in your own cup and your own straw. That's a fine way to share a milkshake. But if you went out with somebody and you got one milkshake with one straw and you took turns drinking it, you'd have to be pretty close to that person. So that is the question-- do babies and toddlers, even before they can talk, use how people share food, or what they're willing to put in their mouth, as a way to figure out who's really close to whom?
ASHLEY THOMAS: And, in fact, saliva sharing is a cue that's used across cultures to distinguish between these types of relationships, so we thought that that would be a really good place to start. The way that you study infants, because you can't ask them questions and get answers from them, so you have to do things like show them videos and measure where they look and for how long they look at something. So what we did is we showed infants videos of people interacting with puppets, and in one of the videos somebody takes a bite of an orange, feeds the puppet, and then takes another bite of the orange. So that's the intimate interaction.
And in the other one, the woman has a perfectly friendly and cooperative interaction with the puppet. She passes a ball back and forth with the puppet, which again is cooperative, it's friendly, but it's not intimate. And the question that we asked is who infants expect to respond to the distress of that puppet?
So we showed those two interactions a bunch of times until we thought that infants had learned that information, and then we showed them both of the women with the puppet in the middle. The puppet cries, and then the thing that we measure is who they look at first, as though they're expecting that person to be the one to respond to that puppet's distress. And what we found is that both infants and toddlers look at the person who had had that saliva sharing interaction, compared to the person who had merely had this cooperative and friendly interaction.
We collected some part of this data before the pandemic hit. And then obviously after the pandemic hit, we couldn't have infants come into the lab anymore, and so we had to shift our testing over Zoom. The nice thing about having that data that we collected before the pandemic is that we know that infants make these inferences without this cultural input of everybody being really concerned about hygiene.
And the nice thing about shifting to Zoom is we were still able to do the studies, we still found the same results. But we were able to reach a much broader population, which is really good, because it both allows us to expand the types of families who are being able to participate in science because it's so much easier to participate over Zoom, but also, it helps us with our claims that we want to make in this paper, which is that infants in the United States make these inferences, not just infants in Cambridge.
REBECCA SAXE: A thing that's really cool about this study is that it's at a meeting point between disciplines. So these questions, how do babies learn the social structure of their environment, how do they learn what family means-- those are traditional questions in anthropology. And the methods that we're using doing little plays on a stage measuring where babies look, those are pretty traditional in developmental psychology, but bringing them together is what I'm so excited about in this study.
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