at NORTHWESTERN UNIVERSITY
Current Studies
Current Studies
The intersection of language and thought in infancy
This line of studies is focused on the effect of words on categorization in the first months of life. We want to trace the developmental trajectory of this effect over the first year of life. The starting point for these studies, is a recent demonstration that words promote object categorization in infants as young as 3 months, and do so in a way that carefully matched tones do not (Ferry, Hespos, & Waxman, 2010). The result opens several new avenues for investigation, each of which will bear on fundamental questions concerning the relation between language and conceptual organization in the first year of life. The project will identify what it is about speech stimuli that promoted object categorization over and above the effect of tone sequences in infants so young. The experiments test the hypothesis that human speech engenders in very young infants a heightened attention to the surrounding objects, and that this very general attentional effect later becomes more specific as infants become attuned to the speech sounds of their own ambient language. Pursing this hypothesis requires an examination of 3- to 12-month-old infants’ treatment of a broad range of auditory stimuli. To discover whether the facilitative effect of words on categorization is specific to linguistic stimuli or evident for other complex stimuli as well, the experiments use a preferential-looking paradigm to investigate the effects of auditory stimuli including naturalistic speech from a range of languages, filtered, backwards, sine-wave speech, mammal vocalizations and bird calls. Another focus of this project is to investigate the developmental trajectory for infants growing up in bilingual homes.
Do infants have different expectations about solid and liquids?
When a cup containing pencils is tipped over, not much happens. However, when a cup containing coffee is tipped over, panic can ensue as one tries to catch the cup before too much coffee spills. These reactions to clumsiness are the result of understanding that solids and liquids have different physical properties and therefore behave differently. These reactions may seem obvious, but when does the expectation that liquids deform to fill the space allotted develop? This line of studies is focused on characterizing the origins and development of knowledge about substances. The starting point for these studies is a recent demonstration that 5-month-old infants have different expectations for solids and liquids (Hespos, Ferry, & Rips, 2009). The results provide a springboard to a new approach to substances like liquids or sand. These experiments map out the nature of substance knowledge in infants using a combination of innovative methods ranging from looking time, reaching, and locomotor tasks. The first series focuses on differences in how objects and substances behave. In the second series, we use a complementary approach and focus on a similarity between the two entities. Quantity discrimination can be applied to both objects and substances and we test whether infants’ number sense for substances shares the same characteristics as quantity discriminations for objects.
Optical Imaging
There is little known about functional brain activation in healthy humans infants. We are elucidating the links between behavioral and neural development using near-infrared spectroscopy (NIRS). NIRS is a new technique for studying infants but it is based on technology used in every hospital worldwide called pulse-oximetry. Most people are familiar with pulse-ox as the clamp that is put over the end of their finger to measure their pulse in a doctor’s office. We use this same technology to measure blood flow in babies brains (it is FDA approved for continuous use). We use NIRS to investigate developmental changes in the major perceptual processing systems (e.g., visual, auditory, and touch). The data provide an exciting step forward in understanding the nature of blood flow changes in the brain as a result of sensory/motor activity. We found there were measureable differences between global brain areas suggesting that even in early infancy the blood flow response is quite specific. There were developmental differences across ages (specifically in the language task), suggesting that this technology can provide a sensitive measure of typical developmental milestones. This project provides a wealth of rich data regarding developmental changes in brain activation during the first year of life. In turn, this research will benefit medical and clinical fields by mapping out the blood flow response in healthy infants; we provide a baseline from which to examine individuals that have atypical development. Ultimately, these procedures could be used for early diagnosis of visual, language, and motor disorders.
