  Psychosocial constructs can only be assessed indirectly, and measures are
typically formed by a combination of indicators that are thought to relate to
the construct. Reflective and formative measurement models offer different
conceptualizations of the relation between the indicators and what is sometimes
conceived of as a univariate latent variable supposed to correspond in some way
to the construct. It is argued that the empirical implications of reflective
and formative models will often be violated by data since the causally relevant
constituents will generally be multivariate, not univariate. These empirical
implications can be formally tested but factor analysis is not adequate to do
so. It is argued that formative models misconstrue the relationship between the
constructed measures and the underlying reality by which causal processes
operate, but that reflective models misconstrue the nature of the underlying
reality itself by typically presuming that the constituents of it that are
causally efficacious are unidimensional. The ensuing problems arising from
these misconstruals are discussed. A causal interpretation is proposed of
associations between constructed measures and various outcomes that is
applicable to both reflective and formative models and is applicable even if
the usual assumptions of these models are violated. An outline for a new model
of the process of measure construction is put forward. Discussion is given to
the practical implications of these observations and proposals for the
provision of definitions, the selection of items, item-by-item analyses, the
construction of measures, and the interpretation of the associations of these
measures with subsequent outcomes.
