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About Bayley Scales of Infant Development Scores

Developed by Nancy Bayley and published under a title of the same name, The Bayley Scales of Infant Development (BSID) is a test that measures the cognitive, motor and behavioral development of children ages 1 month to 3 years. Specifically, the test is used to illustrate the standard development of children within this age range and isolate those with disabilities or delays who might benefit from early intervention. Used worldwide, the test is administered by specially trained professionals and takes approximately 45 to 60 minutes to complete.


Cognitive development is defined by how an infant perceives and learns to interpret his surroundings. Psychologist Jean Piaget, a major influencer in the world of cognitive development, said that it’s mainly through a child’s natural curiosity of his surroundings that he learns to expand his cognitive awareness. Cognitive development encompasses memory, learning, problem solving and the ability to verbally communicate.


There are two types of motor development: cephalocaudal and proximodistal. Cephalocaudal development is an infant’s learning to first control his head, followed by his arms and trunk. Lastly, he learns to manipulate his legs in order to walk. Proximodistal development is the infant’s mastered motor control over the hands and fingers, and it occurs after cephalocaudal development. In other words, a developmentally normal child learns gross motor skills, such as crawling, walking and running, long before he is able to grasp a pencil to write his name.


When experts use the Bayley Scaled of Infant Development test to evaluate behavioral development, they are observing and learning about the child’s temperament. This genetic, ingrained personality appears within the child’s first 2 months of life and is usually indicative of how a child will interact with her world. Experts evaluate the child’s activity, intensity and level of persistence, and how she reacts emotionally.

Special Needs

Aside from providing parents with an idea as to what is typical of a developmentally normal child, the Bayley Scales of Infant Development test is used to identify those children who are delayed in their development and to qualify them for specialized services. The test can then be administered several times over the course of a child’s treatment to chart his progress. It can also be used as a method of teaching and for continued research.


What is considered developmentally normal is based upon data collected from 1,700 infants, toddlers and preschoolers living in the United States. The test is separated into 14 different age groups, and each child’s score is compared to those of the same age. Because the test was initially administered in an unfamiliar setting without the presence of the parents, facilitators determined that unless the child scored very low, the overall test was a poor predictor of how the child would cope in life. It wasn’t until 2004, when parents were asked to provide additional input, that doctors could more truthfully assess the child.

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