The research in our lab addresses how the brains of typically developing children process language to increase our understanding of language acquisition and development. To address these issues we use electrophysiology, analyzed to study the Event Related Potentials, or ERPs, and the neural oscillations that underlie cognitive and linguistic processing in children and adults.
Current Studies and Areas of Interest
How the Brain Learns Words
One of our current projects focuses on how grade school aged children learn new words. Word learning is essential to cognitive and social development across the lifespan. Young children can quickly map new words onto objects or actions in their environment; however, learning using only surrounding linguistic context, the primary method for word learning available to older children and adults, is substantially more difficult and less well researched. For example, how does one identify the meaning of the word gossamer when encountering this sentence from David Herber Lawrence’s Sons and Lovers “Fascinated, he watched the heavy dark drop hang in the glistening cloud, and pull down the gossamer”? In such cases, it is estimated that 4th graders only learn 3-5% of the unfamiliar words that they first encounter when reading, a number that increases slowly with age.
Our current study asks children to listen to sentences that include words they have never heard before and tell us what they think the words mean. As they perform this task, we record their EEG to identify how their brain is engaged to perform the word learning task. One of our primary goals is to identify developmental changes and individual differences in children’s abilities and corresponding neural activation. Identifying how quickly children can identify word meanings and the underlying neural processes engaged when doing so will greatly increase our understanding of vocabulary growth during the school years when learning is imperative to academic success.
How the Brain Differentiates Hammers from Cows
Adults seem to engage different areas of their brain when they identify an object compared to an animal as well as when they hear a word for an object compared to an animal. There are potential evolutionary reasons for this as well as other, contrasting theories about how experience leads to these unique neuronal processes. In this group of studies we want to identify the origins and development of these differences. Children hear a word for an object ("hammer") or an animal ("dog") followed by a picture. They have to identify if the picture matches the word. Our goal is to identify differences and similarities in the processing of words and pictures for objects and animals to help uncover how words and concepts in the brain come to engage the complex, well differentiated system that we find in adults. This will help us to learn more about the brain, language and cognition across the lifespan.
Eye-Tracking and EEG: Are Eyes Really the Window to the Soul?
To compliment our studies on object and animal identification, we are also trying to identify what features children use to differentiate objects from one another, the development of the neurological underpinnings of this feature detection, and how focusing on those features may speed recognition. In this group of studies, as a participant's EEG data is collected we track their eye gaze (using a Tobii 750 Eye-Tracker) while they identify pictures of animals as dogs or non-dogs. Previous studies have found that clearest, most efficient way to differentiate animals is by attending to their head. The goal in this study is to uncover the brain's response at the point when the participant looks at the head to capture information about specific object identification. Such studies provide better insights into how what information children and adults use to categorize and identify information in the environment.
Studies of Nouns and Verbs
Verbs are more difficult for children to learn than nouns. This difference is even larger in children who have language delays or disorders. In our lab we have a series of studies investigating the development of noun and verb knowledge, with the goal of using these results to understand why children with language problems fail to learn verbs and how therapists can help.
When is a picture worth 1000 words? Finding a noun or a verb:
One reason that children have difficulties learning verbs compared to nouns is that verbs can refer to events that all look quite different: a leaf falling out of a tree and an old man falling down on ice are quite distinct from each other even though they both involve the action of “falling.” This stands in contrast to the relative similarity between nouns—i.e. that found between all “leaves” or all “old men.” In addition, a single particular action can also have lots of different verbs that refer to it. A girl leaving a room can be described as “leaving,” “exiting,” “walking,” “stepping out,” or “fleeing.” On the other hand, the noun in this case—the door she walks out of—will probably always be called a door.
To test how matching a verb to an action differs from matching a noun to an object, adults and children who came to the lab listened to a word (noun or verb) that was followed by a picture that contained an object and an action (a man sitting in a chair). They were then asked to indicate whether the word and the subsequent picture matched one another. For adults, this task was easy for both objects and actions, and they answered both items quickly and accurately. Interestingly, when we looked at their brain activity measured by EEG, we found important differences in the processing that followed each type of word. When a verb didn’t match the picture, participants’ brains showed a late response indicating that even when an action wasn’t identified quickly, the adults checked the picture again to be sure it didn’t fit some other aspect of the picture (similar to walking or exiting). This did not happen when the noun did not match the object. If an object wasn’t in the picture, there was no need to check again. It seems that a picture is indeed worth 1000 verbs, but many fewer nouns. The findings with adults are currently under review by a scientific journal that focuses on adult neurocognitive abilities.
This finding sheds some light on why children have problems with verbs. Even in a seemingly very simple task, college students had to think twice about the verb meanings. This is likely much more difficult for a 3 or 4 year old, just learning how to label all of the actions and events in the world. We are still working on this study with children. We want to know if children show similar or different responses for verbs nouns and verbs compared to adults. Hopefully, when we have enough participants, we will know the answer!
Grammatical Processing in Typically Developing Children and Those with Language Delays
Not only do children with language delays have problems identifying verbs compared to nouns, but they have problems using verbs correctly in sentences. For example, children with Specific Language Impairment (SLI), a disorder diagnosed in 7% of children, are more likely to say sentences with verb phrase errors ("She walk to the store") than with noun phrase errors ("She walks to store"). Researchers and speech therapists have struggled to identify if this is a problem in processing the verb phrases or in producing them. We are currently conducting a group of projects to study this question. We are comparing how children with SLI and children without the disorder process each word in an ongoing sentence as well as how they respond to relatively subtle grammatical errors. In adults and typically developing children, the brain responds to grammatical errors in a very typical way, with an increase is positive electric potential at about 600 milliseconds after one hears the mistake. By comparing these findings to the brain responses of children with SLI we can better understand if their problems stem from processing or production difficulties. This will have important implications for future treatments.
So far we found that even adults have much more robust brain responses to noun errors than verb errors. It is no wonder that children, especially those who are struggling already, are having greater difficulty producing these grammatical features correctly. We are currently still collecting data with children.