During the course of development, human infants gather information about the external world without the benefit of an extensive base of knowledge that adults automatically bring to bear on perceptual, motor, cognitive, and language tasks. What mechanisms allow infants to acquire this initial level of information and how does that information guide subsequent learning? Clearly, most learning that occurs in infancy, and a substantial amount of learning in adulthood, is performed without instruction—it is implicit and based on an analysis of the distributional properties of environmental stimulation.
For over a decade, my research has been directed at exploring and understanding these implicit learning mechanisms, which are typically referred to as "statistical learning". Although initially studied in the task of word segmentation from fluent speech, statistical learning has been extended to other domains, such as musical tones, phonetic categories, sequences of visual shapes, sequences of motor responses, and combinations of objects (or object parts) in complex visual scenes. An important goal of these studies is to reveal the computational constraints that enable statistical learning to be tractable given the complexity of the input and the infinite number of statistical computations that are possible over any set of inputs. Initial computational models of statistical learning focused on bi-gram statistics and conditional probabilities, but more recent work has broadened to include Bayesian ideal learning models. Empirical studies of statistical learning have also evolved to explore order effects in learning multiple structures and to understand how statistical patterns trigger the formation of categories.
A related line of research focuses on spoken word recognition in both infants, toddlers, and adults using eye-tracking methods. Once an auditory word-form has been extracted from fluent speech, how does the infant map that sequence of sounds onto meaning? Recent and on-going studies have examined how infants and toddlers recognize the meaning of the unfolding speech signal, for both previously known and recently learned words, as well as for mispronounced words or words preceded by a disfluency. Most of these studies employ one of three Tobii eye-trackers, while others that are just beginning use a novel head-mounted eye-tracker in combination with a LENA audio-recording and analysis system. Studies of adults employ an artificial lexicon paradigm and the visual world eye-tracking paradigm to carefully control variables such as word frequency and acoustic similarity (neighborhood structure).
In the past few years, my research has moved toward studies of brain function in adults and infants using fMRI and optical imaging, respectively. A new 3T magnet facility (http://www.rcbi.rochester.edu) has enabled us to measure activations in a targeted brain area, such as MT/MST, to novel words that have been linked during a lexical learning task to referents which have the property of motion. This allows us to determine if similar sounding words also activate MT/MST even if they do not have the referential property of motion, thereby serving as a measure of lexical competition. An optical imaging system (Hitachi ETG-4000) provides a 48-channel measure of hemodynamic activity in the superficial layers of cortex while infants are being presented with controlled stimulation. This system enables us to assess activations in various regions of the infant brain, thereby revealing the neural correlates of behavioral measures such as looking time. We are particularly interested in how these optical signals change over time as a way of understanding aspects of habituation and statistical learning.
UndergraduateBCS 172 Development of Mind and Brain, Syllabus
BCS 205 Lab in Development
GraduateBCS 599 Professional Development and Career Planning
Featured PublicationsEmberson, L. L., Richards, J. E., and Aslin, R. N. (2015). Top-down modulation in the infant brain: Learning-induced expectations rapidly affect the sensory cortex at 6 months. Proceedings of the National Academy of Sciences, 112, 9585-9590.
Aslin, R. N., Shukla, M, & Emberson, L. L. (2015). Hemodynamic correlates of cognition in human infants. Annual Review of Psychology, 66, 349–79.
Aslin, R. N. (2014). Infant learning: Historical, conceptual, and methodological challenges. Infancy, 19, 2-27.
Selected PublicationsIn Press Bankieris, K. R. and Aslin, R. N. (in press). Implicit associative learning in synesthetes and non-synesthetes. Psychonomic Bulletin & Review.
Aslin, R. N. (in press). Statistical learning: A powerful mechanism that operates by mere exposure. WIREs Cognitive Science, Special Issue on Development. [doi: 10.1002/wcs.1373]