Nancy Bayley

Bayley was born on September 28, 1899, in Dalles, Oregon. She was the fourth of five children born to Prudence Cooper Bayley and Fredrick W. Bayley.^[1] She came from a family of pioneers.^[4] Until the age of 8, Bayley was a sickly child and could not attend school.^[2] Yet, even with her delayed enrollment at public school, she quickly caught up.^[4] Later, she enrolled in the University of Washington to become an English teacher, but after taking an introductory psychology course she changed her path.^[2] In 1922, she completed her Bachelor of Science in psychology, which was followed by a Master of Science in the same field in 1924.^[2] During her years at the University of Washington, she got the opportunity to work as a laboratory assistant in the Gatzert Foundation for Child Welfare.^[4] Bayley earned her doctoral degree at the University of Iowa in 1926.

Bayley started her career in 1926 at the University of Wyoming, where she was an instructor until 1928. There she published her first of almost 200 papers. In 1928, Bayley moved to the University of California, Berkeley, to work in the Institute of Child Welfare. It was here that Bayley began work on the Berkeley Growth Study. On April 7, 1929, she married her husband, John, R. Reid. He was at the University of California, Berkeley completing his own doctoral work in philosophy. In 1954, she went to the National Institute of Mental Health in Bethesda, Maryland, where she worked on child development in the Laboratory of Psychology. In 1964, Bayley returned to Berkeley and published the Bayley Scales of Infant Development. She retired in 1968 but continued to revise the Bayley Scales of Infant Development.^[4] Bayley and her husband lived the remainder of their lives in Carmel, California. She died at the age of 95 from respiratory illness.^[1]

In 1928, Bayley began work at the Institute for Child Welfare at the University of California, Berkeley, on what is referred to as the Berkeley Growth Study.^[5] The study aimed to study human development from infancy to adulthood on a range of physical, psychological, and physiological characteristics.^[1][2][3][5] Bayley became the director of the program in 1931.^[3] Through her efforts, Bayley was able to publish the California First-Year Mental Scale in 1933 and the California Infant Scale of Motor Development in 1936, precursors to her later Bayley Scales of Infant Development.^[2]

The Berkeley Growth Study had 61 participating children born between September 25, 1928, and May 15, 1929.^[2][3] The children were white, raised in English-speaking homes within the Berkeley area, and were of above average socioeconomic status.^[3] Measurements began four days after birth, at which time all children were considered to be of normal health. The sample decreased to 42 participating children by 1941, due primarily to family relocation.

Source:^[3]

Bayley assessed the children on their physical, motor, mental, and physiological development. An analysis of trends in the data was then conducted, with particular reference to the age of developments, as well as a correlational investigation of relating factors. Assessments were conducted once a month from birth to 15 months, once every three months from 15 to 36 months, and every six months after 36 months. Initial measurements focused on reflexes and bodily measurements, such as blood pressure and breathing rates. Additionally, information was gathered regarding the maternal and prenatal history. Subsequent assessments were conducted at the Institute for Child Welfare, as well as at home visits, pediatric centers, and at play-based field group outings.

Mental measurements included the California First-Year Mental Scale, the California Pre-school Mental Scale, vocabulary tests, and Stanford-Binet intelligence tests. Motor assessments examined speed, dexterity, and reflexes, amongst other things. Participants completed the California Infant Scale of Motor Development, as well as examinations of footprint records. Physiological tests assessed exercise and exertion abilities, the galvanic skin reflex, and metabolism. Additional assessments involved body dimensions, x-rays, and tests of emotion and personality.

Variations in intelligence across the lifespan led Bayley to conclude that intelligence is not fixed at birth, but instead impacted by encounters with environmental factors.^[5] Bayley thus argued that hindrances in development stemmed from social influences, such as poverty, rather than psychological influences.^{[citation needed]} Other factors Bayley considered vitally important to development were parenting attitudes and behaviors.^{[citation needed]} Examinations of x-rays and physiological growth led Bayley to become the first scientist to recognize the predictability of adult height based on infant size.^{[citation needed]} Additionally, Bayley discovered no gender differences in terms of physical and psychological development.^{[citation needed]}

Measures of assessment were later published by Bayley, including the California First-Year Mental Scale and the California Infant Scale of Motor Development, which collectively lead to the development of the Bayley Scales of Infant Development.^[2]