When you see the photo here, you probably assume the kids are siblings, or at least very close friends. It's not the matching dresses--it's because they're taking turns tasting the same ice cream cone--an activity in which they'll undoubtedly exchange saliva. We humans tend to conclude that people willing to share spit with each other are probably more intimately related.
Do babies realize the same thing? Apparently so! Here's an NPR story about a research study on whether babies also conclude that people who share saliva also conclude that they are more closely related. They introduce the story like this:
"From a really young age, without much experience at all with these things, infants are able to understand not only who is connected but how they are connected," says Ashley Thomas of MIT, who studies what babies and young children understand about the complexities of their social world. "They are able to distinguish between different kinds of cooperative relationships."
As is usually the case, researchers have to get creative to study what young kids think. The present set of studies tested both infants (aged 8-10 months) and young toddlers. They used a puppet show to experimentally manipulate different variables:
One of their videos shows a woman rolling a ball back and forth with a blue fuzzy puppet. Then another woman shares an orange with that same puppet by putting a slice of orange in her mouth, then letting the puppet nibble on the slice, and then putting it back in her own mouth.
Then they used looking time to measure what infants were thinking:
...the video then shows the two women with the blue fuzzy puppet in between them. The puppet starts to cry and puts its head down, as if it is suddenly unhappy.
When the puppet cried, infants and toddlers looked first and looked longer at the woman who had shared bites of her orange.
"They're looking in that direction because they expect something to happen there," says Thomas. "They expect that woman to be the one to respond to the puppet's distress."
Questions:
a) What is the independent variable (IV) in this experiment? What were its levels? Is it manipulated as independent-groups or within groups?
b) What is the dependent variable (DV)?
c) Which of the four simple experiments does this seem to be--pretest-posttest? posttest only? concurrent measures? or repeated measures?
d) Sketch a bar graph of the results, putting the IV on the x-axis and the DV on the y-axis.
Here's another part of the study:
When the two women were shown with a totally new puppet that started to cry, however, infants and young children looked at both women equally often. This suggested that they didn't see this particular food-sharing woman as especially helpful; instead, her relationship with the puppet was what really mattered.
e) Sketch a bar graph of these results, putting the IV on the x-axis and the DV on the y-axis.
Like most modern research articles, this one includes multiple studies (three studies, in fact). Additional studies help provide replications of the observed effects, and can also help rule out alternative explanations. Here is the journalist's description of one of the other studies in the empirical journal article:
To make sure it wasn't just sharing of food that seemed to make babies infer the existence of a close social connection, the researchers created another, similar video. This time, instead of sharing an orange slice, a woman simply put her finger in her own mouth and then put it in a purple puppet's mouth, before putting it back in her own mouth.
Then that same woman also interacted with a green puppet, touching its forehead and then touching her own forehead. After that, the video showed the woman seemingly in distress, with the purple and green puppets looking on.
Infants and toddlers gazed at the purple puppet that had the more intimate, finger-in-the-mouth interaction, as if expecting this puppet to be more affected by the woman's consternation, presumably because they seemed to have a closer relationship.
f) What are the IVs and DVs in this new study?
g) Sketch a bar graph of the results being described.
h) What type of replication is this: a direct replication, a conceptual replication, or a replication-plus-extension?
i) One possible explanation for the infants' looking behavior in this study is that infants just prefer to look at purple puppets more than green puppets. How could the researchers rule out this alternative explanation?
Want to read more? here's a link to the empirical journal article, which appeared in the journal Science.
