This is the seventh of eight blog posts written by undergraduates in PSY102: Introduction to Cognitive Psychology, Summer Term I 2019.

Let’s say you visit your grandmother later today and come across a bowl of unknown exotic berries that look and taste similar to a raspberry. Your grandmother tells you that they are called bayberries. How would your mind react to the new word “bayberry”?

Research shows that an adult brain would probably categorize the word “bayberry” into the category of berries, and draw connections between “bayberry” and other related berry names.

But how do you think an infant would deal with a word like “bayberry”? Would he or she categorize the word the same way you would?

Elika Bergelson, a developmental psychologist at Duke University, provided some possible answers for this question in a study published in the Proceedings of National Academy of Sciences.

Six-month-old infants were shown two objects on a screen simultaneously, as a speaker provided labeling for one of the objects (eg. Look at the dog!).

The thing on the right is a shoe, sweetie. We’re not sure about that other thing…

The two objects were either literally related or unrelated. For example, the words nose and mouth are semantically, or literally, related since they both refer to body parts, while the words nose and boots are semantically unrelated.

As the babies were presented with these objects, their eye movements were tracked. The longer a baby stared at an object, the more confident he or she is presumed to be about the object’s match with the label. This acted as an indicator of how well the baby understood which object the label was referring to.

If the infants categorized words into semantically related groups, then they’d be more likely to confuse objects that are related. This means that the infants would perform better at choosing the correct object when the objects are unrelated.

The results suggest that infants approach words no differently than adults. The babies correctly identified the labeled object more frequently when the two were unrelated than when the two objects were related. This indicates that babies have the mental representation of words categorized into semantically related groups. When encountering two unrelated objects, babies can quickly distinguish between the two objects because they do not belong to the same mental category.

Elika Bergelson

However, when the two objects are related, the infants often confuse them with each other because they belong to the same or closely related categories — while 6-month-olds have developed a general categorization of nouns, their categories remain broad and unrefined, which causes the boundaries between objects in the same category to be unclear.

So what do all these results mean? Well, back to the bayberry example, it means that a 6-month-old will place the word “bayberry” into his or her mental category of “berries.” He or she might not be able to distinguish bayberries from raspberries the next time you mention the word “bayberry,” but he or she will definitely not point to bayberries when you drop the word “milk” or “car.”

Toddler Rock

If the results of this study can be replicated, it means that the infant approach to language is much more similar to adults than researchers previously thought; the infants have already developed a deep understanding of semantics that resembles grown-ups much earlier than researchers previously speculated.

While the results are exciting, there are limitations to the study. In addition to the small sample size, the infants mainly came from upper middle class families with highly educated parents. Parents in these families tend to spend more time with their infant and expose the infant with more words than parents with lower socio-economic status. So these findings might not be representative of the entire infant population. Nevertheless, the study sheds light on how infants approach and acquire words. It’s also possible this finding could become a new way to detect language delay in infants by the age of six-months.

Guest post by Jing Liu, a psychology and neuroscience major, Trinity 2022.