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Marsha Clarkson

Ph.D., University of Florida, 1979
Associate Professor
Member, Developmental Psychology and NBN Programs

mclarkson@gsu.edu
404-413-6262
752 Urban Life

As a developmental psychologist and psychoacoustician, my primary professional interest is in describing and understanding the development of auditory processing in infants and children. A common theme underlying all of my work is how the developing auditory system influences infants’ and children’s emerging auditory capacities. In particular, my work has focused on pitch perception and auditory localization skills in infants and on auditory temporal processing in children diagnosed with phonological or reading disabilities.

Although adults use variations in the pitch contours of speech to communicate with young infants, relatively little is known about infants’ pitch perception. Our work with 2- to 7-month-old infants shows that by 7 months of age infants can identify and discriminate the pitches of a variety of complex sounds. Infants appear to rely upon many of the same acoustic cues as do adults to hear pitch. Nonetheless, the strength of infants’ percept of pitch appears weaker than that of adults with infants proving incapable of hearing the pitch of some sounds for which pitch is easily detected by adults. Current work is using an iterated rippled noise stimulus to measure thresholds of pitch strength in infants and adults.

The ability of organisms to locate sound sources is nearly universal among animals who hear, and we have found that even newborn infants can detect the general location of sound sources. While both infants and adults appear to use the same cues for locating sounds, infants’ use of those cues is less accurate than that of adults. We have measured the acuity of sound localization in 2-, 6-, and 18-month-old infants under a variety of stimulus conditions. Infants prove particularly poor a pinpointing the sources of brief sounds, and even at 18 months of age are significantly poorer than adults.

Previous research has posited that children diagnosed with a reading disability or a phonological deficit show deficits in auditory temporal processing. We have been assessing performance on auditory tasks in 6- to 9-year-old children, some of whom have been diagnosed with a reading disability and some of whom have normally-developing reading skills. The presence of a reading disability predicts children’s performance on auditory backward masking tasks believed to tap temporal processing and spectral resolution. Thresholds for detecting a signal in the presence of those masking noises are elevated in children with a reading disability. Although reading disability does not predict the ability of children to locate strongly echoing sounds, it does negatively impact children’s ability to judge the temporal order of sounds. Current work is looking at comodulation masking release (CMR), an auditory phenomenon that allows listeners to separate signals from noise in the natural environment through perceptual grouping of different stimuli, in normally-developing children and in children diagnosed with a reading disability. The CMR task taps both auditory temporal processing and cross-frequency processing. A collaborative project with Dr. Bruce Pennington at the University of Denver is assessing auditory masking abilities in 5- to 9-year-old children diagnosed with a phonological deficit (PD) and comparing that performance to normally-developing children. For those 5-year-old children who can learn to perform a masking task, backward masking thresholds of PD children are elevated relative to normally-developing children. These same children are now 7 years of age and are being testing in the same auditory masking protocol.

At the undergraduate level I teach Natural Science Aspects of Psychology, Developmental Psychology, and Sensation and Perception, and at the graduate level I teach courses in Sensation and Perception, and Infancy, and a seminar in Perceptual Development.

Within the Psychology Department, I am a member of both the Developmental Psychology Program and the Neuropsychology and Behavioral Neurosciences Program, and I serve on the departmental executive committee. Within the university, I participate as a member of the Center for Research in Atypical Development and Learning (CRADL) and the Center for Brain and Health Sciences. Professionally, I am a member of the International Society for Infant Studies, the Society for Research in Child Development, the Association for Research in Otolaryngology, and the Acoustical Society of America where I serve on the technical committee for Psychological and Physiological Acoustics.

Representative Publications and Presentations

Montgomery, C. R., Zettler, C. M., Morris, R. D., Sevcik, R. A., & Clarkson, M. G. (February, 2003). Auditory processing in children with reading disabilities: Temporal order judgments. Paper presented at the Annual Meeting of the International Neuropsychological Society, Honolulu, Hawaii.

Clarkson, M. G., Zettler, C. M., Follmer, M. J., & Takagi, M. J. (December, 2002). Estimates of the strength of repetition pitch in infants. Paper presented at the 144th Meeting of the Acoustical Society of America, Cancun, Mexico..

Raitano, N., Tunick, R., Pennington, B., & Clarkson, M. G. (February, 2002). Temporal auditory processing in children with speech/language disorders. Paper presented at the Annual Meeting of the International Neuropsychological Society, Toronto, Ontario, Canada.

Clarkson, M. G., & Montgomery, C. R. (July, 2000). Precision of infants’ localization of brief sounds. Paper presented at the Biennial International Conference on Infancy Studies, Brighton, England

Montgomery, C. R., & Clarkson, M. G. (1997). Infants' perception of pitch: Masking by low- and high-frequency noises. Journal of the Acoustical Society of America, 102, 3665-3672.

Clarkson, M. G. (1996). Infants' perception of intensity: Spectral profiles. Infant Behavior and Development, 19, 181-190.

Clarkson, M. G., Martin, R. L., & Miciek, S. G. (1996). Infants' perception of pitch: Number of harmonics. Infant Behavior and Development, 19, 191-197.