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Preface
All three of us—Luca Mari, Mark Wilson, and Andrew Maul—have dedicated our
careers to the topic of measurement, albeit in substantially different areas of application. Luca has a background in physics and engineering and works in the field of
metrology, usually defined simply as the scientific study of measurement, but which
has until recently almost exclusively entailed the study of physical measurement.
Mark and Andy have backgrounds in education and psychology, and work in the
field of psychometrics, usually defined as the scientific study of psychological measurement. Given the clear overlap of content, one might expect that the fields of
metrology and psychometrics would have a close relationship, and perhaps even
that the latter would be a subfield of the former. But this is not the case: indeed, in
our experience, many professional metrologists and psychometricians are unaware
of the very existence of the other field—including the three of us, until our interests
happened to lead us each, for different but overlapping reasons, to become concerned with the very possibility of a common foundation of measurement theory
and practice.
To put the core issue as briefly as possible: What is it that makes a given process
a measurement? In particular, can psychological and social properties, such as wellbeing and reading comprehension ability, truly be measured, as is frequently
claimed by human scientists and educational testing professionals, and if so, in what
way are such processes related to the measurement of physical properties such as
length or temperature? Are there shared elements of measurement processes across
different domains of application? If so, why have the fields of psychometrics and
metrology historically been so disconnected? And if not, are claims about the measurability of psychosocial properties well justified, or even coherent, given the way
measurement is broadly understood in both scientific and lay communities?
To help clarify what we think is at stake with respect to this last question, consider the implications of presenting a given claim or value as being the result of a
measurement process. “I have measured your child’s reading comprehension ability” is usually understood as having a different meaning than “I have formed an
opinion about your child’s reading comprehension ability”. Relatedly (but not identically, as we will argue), framing claims in numerical terms (e.g., “your child’s
Preface
All three of us—Luca Mari, Mark Wilson, and Andrew Maul—have dedicated our
careers to the topic of measurement, albeit in substantially different areas of application. Luca has a background in physics and engineering and works in the field of
metrology, usually defined simply as the scientific study of measurement, but which
has until recently almost exclusively entailed the study of physical measurement.
Mark and Andy have backgrounds in education and psychology, and work in the
field of psychometrics, usually defined as the scientific study of psychological measurement. Given the clear overlap of content, one might expect that the fields of
metrology and psychometrics would have a close relationship, and perhaps even
that the latter would be a subfield of the former. But this is not the case: indeed, in
our experience, many professional metrologists and psychometricians are unaware
of the very existence of the other field—including the three of us, until our interests
happened to lead us each, for different but overlapping reasons, to become concerned with the very possibility of a common foundation of measurement theory
and practice.
To put the core issue as briefly as possible: What is it that makes a given process
a measurement? In particular, can psychological and social properties, such as wellbeing and reading comprehension ability, truly be measured, as is frequently
claimed by human scientists and educational testing professionals, and if so, in what
way are such processes related to the measurement of physical properties such as
length or temperature? Are there shared elements of measurement processes across
different domains of application? If so, why have the fields of psychometrics and
metrology historically been so disconnected? And if not, are claims about the measurability of psychosocial properties well justified, or even coherent, given the way
measurement is broadly understood in both scientific and lay communities?
To help clarify what we think is at stake with respect to this last question, consider the implications of presenting a given claim or value as being the result of a
measurement process. “I have measured your child’s reading comprehension ability” is usually understood as having a different meaning than “I have formed an
opinion about your child’s reading comprehension ability”. Relatedly (but not identically, as we will argue), framing claims in numerical terms (e.g., “your child’s