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Descriptive research is an observational approach designed to document traits, behaviors, and conditions of individuals, groups, and populations. Descriptive and exploratory elements are often combined, depending on how the investigator conceptualizes the research question. These studies document the nature of existing phenomena using both quantitative and qualitative methods and describe how variables change over time. They will generally be structured around a set of guiding questions or research objectives, often to serve as a basis for research hypotheses or theoretical propositions that can be tested using exploratory or explanatory techniques.

Descriptive studies may involve prospective or retrospective data collection and may be designed using longitudinal or cross-sectional methods. Surveys and secondary analysis of clinical databases are often used as sources of data for descriptive analysis. Several types of research can be categorized as descriptive based on their primary purpose, including developmental research, normative research, case reports, and historical research.

Developmental Research

Concepts of human development, whether they are related to cognition, perceptual-motor control, communication, physiological change, or psychological processes, are important elements of a clinical knowledge base. Valid interpretation of clinical outcomes depends on our ability to develop a clear picture of those we treat, their characteristics, and performance expectations under different conditions. Developmental research involves the description of developmental change and the sequencing of behaviors in people over time.

Developmental studies have contributed to the theoretical foundations of clinical practice in many ways. For example, the classic descriptive studies of Gesell and Amatruda1 and McGraw2 provide the basis for much of the research on sequencing of motor development in infants and children. Erikson’s studies of life span development have contributed to an understanding of psychological growth through old age.3 Understanding how behavior naturally changes provides a basis for creation of measuring instruments to determine if an individual’s development is progressing as expected.

Longitudinal Studies

Developmental studies can be characterized by the time period within which changes are documented. The longitudinal method involves collecting data over an extended period to document behaviors as they vary over time. The nature of the population must be specified to define the group to which results will apply.


One of the earliest developmental studies was actually a longitudinal case report of data collected between 1759 and 1777, chronicling the physical growth of a child at 6-month intervals from birth to 18 years.4 These data still represent one of the most famous records of human growth.

Intellectual growth has been the subject of many longitudinal studies in children5 and adults.6 Changes that occur in psychological and physiological processes as people age are best described using longitudinal methods (see Focus on Evidence 20-1).

image Focus on Evidence 20–1

Developmental Trajectories in Children with Autism



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