What is measurement?
The first version of this article was written in 2002, shortly after Dr.Dawson completed her post-doc, in which she spent 4 years exploring the possibility of developing a true measure of human mental development.
Measurement is a process used to determine the amount, size, or degree of a unidimensional, context-independent phenomenon (like temperature, length, weight, or time). It requires:
- a system for assessing the amount of the trait;
- determinations of the accuracy of measurements; and
- the calibration of a standardized measure.
Good thermometers have all of the qualities of a good measure. They are well-calibrated instruments that can be employed to accurately and reliably measure a unidimensional trait across a wide range of contexts.
Good measures make scientific progress possible by ensuring that scientists in a given field are speaking a common language.
From observations to measures
The road from observation to the calibration of a true measure is a long one. For example, the origins of the thermometer appeared in the form of early qualitative observations about relative temperatures (hot as boiling water, cold as ice, hot as fire.) After thousands of years of qualitative observations of temperature, early scientists began to study the phenomenon in earnest. Eventually, a variety of early thermometers were developed, implemented, and refined. Today, all thermometers are calibrated to one of 3 scales—fahrenheigt, kelvin, or celsius. They can be used to measure the temperature of any substance, and they are used widely in every industry, in our homes, and in the devices we use each day. Most of what we are able to do in the 21st century has been made possible by the development of measures like the thermometer. In fact, advances in measurement have preceded every major advance in science.
Measuring mental development
What if cognitive scientists had access to an accurate, valid, and reliable general measure of mental development, one that spanned the developmental continuum from birth through adulthood? What might be some of the implications for developmental research and education?
In the 19th century, James Mark Baldwin described a series of developmental levels in children's and adolescents' reasoning abilities. He saw each of these levels as changes in the way individuals thought, not just what they thought. In the 20th century, scientists like Jean Piaget expanded upon these insights, describing several different ways of thinking that built upon one another over the course of childhood and adolescence. During the 1970's and 1980's, researchers like Karen Kitchener, Patricia King, Lawrence Kohlberg, Robert Kegan, Cheryl Armon, and Kurt Fischer documented similar changes in adulthood.
In the late 1990's, Dr. Theo Dawson undertook the task of translating the qualitative descriptions of developmental levels provided by these researchers into a quantitative, content-independent measure of cognitive development. The first steps were the creation of a human scoring system called the Lectical Assessment System (LAS) and a feasibility study for a computerized developmental scoring system called LAAS.
After many years of research, in February of 2026 we finally introduced a standardized and prescriptive version of CLAS.
Today, we use our human scoring system, LAS, to study the development of social hierarchies and pre-verbal development. CLAS is used to score texts.
Uses of CLAS
CLAS can be used to score the complexity level of just about any text, and with the help of Google Translate, this includes texts written in any common language. This means that CLAS can be used in a wide range of educational, research, and assessment contexts. At Lectica, it is used in developmental research, curriculum evaluation, assessment, selection, growth-monitoring, and the diagnosis of developmental problems.
CLAS is agnostic to specific conceptual content. Indeed, there are an indefinite number of ways to receive a particular CLAS score. This means we can use CLAS scores to legitimately ask questions about the relation between mental development and things like spirituality, wealth, curricula, self-regulation, moral behavior, and critical thinking skills.
The content-independence of CLAS also means it can be employed to determine level of mental development in any knowledge domain—just as thermometers can be used to check the temperature of any substance.