Nancy Bayley

An American developmental psychologist known for her Scales of Mental and Motor Development.

The third of five children of Prudence Cooper and Frederick W. Bayley, Nancy Bayley was born in The Dalles, Oregon, on September 28, 1899. She and her siblings were delivered by her aunt who had become a country physician after her husband died. Bayley's father was head of the grocery in a department store in The Dalles. Childhood illness prevented Bayley from attending school until she was eight, but she quickly made up the missed grades and completed high school in The Dalles.

Defines her niche in developmental psychology

Although she entered the University of Washington in Seattle with plans to become an English teacher, Bayley quickly switched to psychology after taking an introductory course with E. B. Guthrie. She earned her B.S. degree in 1922 and her M.S. degree two years later, while serving as a research assistant at the Gatzert Foundation for Child Welfare at the university. For her master's thesis, “Performance Tests for Three, Four, and Five Year Old Children,” written under the supervision of Stevenson Smith, Bayley devised performance tests for preschoolers, a subject that would occupy her for the rest of her life. A graduate fellowship then took Bayley to the State University of Iowa (now the University of Iowa) in Iowa City where she earned her doctoral degree in 1926. For her Ph.D. dissertation, Bayley used the newly invented galvanometer to measure electrical skin responses to fear in children. It was one of the first studies of its kind.

In 1926, as an instructor at the University of Wyoming, Bayley published the first of her nearly 200 contributions to literature on psychology. Two years later, Harold Jones invited her to become a research associate at the Institute of Child Welfare (now the Institute of Human Development) at the University of California at Berkeley. Bayley remained there for most of her career. At Berkeley she met John R. Reid, a doctoral candidate in philosophy. They married in 1929, and Reid joined Bayley at the Institute. While at Berkeley, Bayley taught a course on developmental assessment of infants and small children in the Department of Psychology and held concurrent research positions in psychology and anatomy at Stanford University.

Initiates study of infant development

At the institute, Bayley began a major study of normal and handicapped infant development. It became known as the Berkeley Growth Study. Her 1933 publication, The California First-Year Mental Scale, was followed in 1936 by The California Infant Scale of Motor Development. In these works, Bayley introduced methodologies for assessing infant development. Likewise, her 1933 publication, Mental Growth during the First Three Years, became a milestone in developmental psychology. Bayley earned the G. Stanley Hall Award of the APA's Division of Developmental Psychology in 1971.

In 1954, Bayley became head of child development in the Laboratory of Psychology at the National Institute of Mental Health in Bethesda, Maryland. There she worked on the National Collaborative Perinatal Project, a study of 50,000 children from birth to age eight. The study examined neurological and psychological disorders, including cerebral palsy and mental retardation. The newly revised Bayley Mental and Motor Scales were used to assess the development of hundreds of children from 1 to 18 months of age. Many surviving subjects of this study continued to participate in follow-up studies. Among her many findings, Bayley demonstrated that there are no sexrelated differences in physical and mental development. She continued to work on this project after returning to Berkeley as the first head of the Harold E. Jones Child Study Center at the Institute of Human Development. She also acted as consultant on a study of infants with Down syndrome at the Sonoma State Hospital in California.

Bayley's work was remarkable for its interdisciplinary nature. In 1951 she coauthored a paper with Mary Cover Jones on the relationships between physical development and behavior. Bayley was the first scientist to correlate infant size with eventual adult size, and in 1946 she published tables for predicting adult height. She was interested in physical differences between the sexes and in androgynous characteristics that were intermediate between male and female traits. She studied the development of emotions in children and the maintenance of intellectual abilities throughout adulthood. Bayley also studied the impact of maternal behaviors on children. She argued forcefully that poor development in children was the result of poverty and other social factors, rather than psychological factors.

See also Bayley Scales of Infant Development.



Bayley, Nancy. The California First-Year Mental Scale. Berkeley: University of California Press, 1933.

Winders, Patricia C. Gross Motor Skills for Children with Down Syndrome: A Guide for Parents and Professionals, 2nd ed. Bethesda, MD: Woodbine House, 2014.


Jackson, BJ, et al. “Bayley Scales of Infant Development Screening Test-Gross Motor Subtest: Efficacy in Determining Need for Services.” Pediatric Physical Therapy 24, no.1 (2012): 58–62.

Spencer-Smith, Megan M., et al. “Bayley-III Cognitive and Language Scales in Preterm Children.” Pediatrics 135, no.1 (2012): 58–62.


Psychology's Feminist Voices. “Nancy Bayley.” (accessed July 22, 2015).

UC Berkeley Institute of Human Development. “Nancy Bayley.” (accessed July 22, 2015).