Speech communication is as effortless as it is essential to everyday life, but this effortlessness belies remarkable complexity. Meaning is encoded in abstract linguistic structure, this structure is transformed into a physical signal, and this signal is perceptually decoded. An adult native speaker readily implements linguistic structure in production, unconsciously executing subtle motor control plans and producing multidimensional acoustic signals. The adult native listener, in turn, automatically maps these signals back onto abstract cognitive structures.
My research focuses primarily on elucidating the nature of linguistic categories in speech production and perception. Through the development and application of innovative quantitative models and closely associated experimental procedures, I analyze the implementation of multidimensional phonological structure. In speech production, my work focuses on the many-to-many mapping between phonological categories and associated acoustic cues and how this mapping varies across languages and higher-level linguistic structures. In speech perception, I focus on modeling the perceptual relationships between abstract phonological dimensions and how these relationships are influenced by signal properties, higher-level linguistic structure, and the cognitive characteristics of the listener.
Of course, speech communication isn’t always effortless. People often have difficulty accurately producing and perceiving speech sounds from a non-native language, and speech perception is a unique challenge for children acquiring a first language and people with sensory or cognitive impairments. My current perceptual research probes the relationships between non-native phoneme discrimination, phonological working memory, and second language word learning. I am also currently collaborating on an investigation of phonological perception and lexical development in children with and without hearing impairment.
However, my interest in complex cognitive processing is not limited to speech communication. I am also collaborating on a number of projects spanning a range of cognitive psychological domains. I am involved in two closely related projects focused on individual differences in cognitive abilities and second language learning. One of these is aimed at understanding the cognitive abilities that enable high-level second language learning. The other is aimed at determining the set of cognitive measures that are most useful in predicting foreign language learning success at the Defense Language Institute. I am also working on an investigation of perceptual adaptation and the perception of cues to racial categories in face perception, as well as a series of studies of how people judge the magnitudes of large numbers.
Finally, much of this empirical research has been enabled, at least in part, by the methodological and theoretical component of my research program. Much of my perceptual work makes use of mathematical refinements and extensions of multidimensional signal detection theory (also known as general recognition theory). A number of projects have also benefited from multilevel Bayesian extensions of various models of perception and decision-making, and my work on cognitive abilities and language learning relies on an innovative techniques for dealing with missing data and sample restrictions.