In a recent study, we empirically demonstrated limitations
in traditional ways that psychologists have used factor analysis to
define cognitive constructs (Delis et al.,
2003). Our criticism of factor analysis was not directed at this
statistical method per se, but rather at how it has often been employed
by psychologists to test cognitive constructs. Specifically, we pointed
out shortcomings in using this technique with normal or mixed
clinical populations. We argued that the factor-analytic studies
of memory tests with normal or mixed clinical populations often yielded
solutions in which measures of immediate and delayed memory loaded on
the same factor. This particular use of factor analysis can mask
important distinctions between critical cognitive functions that have
been demonstrated using other research methods, such as experimental
manipulations or case studies. We then conducted a factor-analytic
study that empirically demonstrated that, whereas immediate and delayed
memory measures load on the same factor when using normal or mixed
clinical samples, these measures load on separate factors when
using a homogenous population of patients with Alzheimer's disease
(AD). We drew the conclusion that factor analytic techniques can still
be used as one method for exploring conceptual relationships,
but only if these methods are used as part of a systematic,
programmatic exploration involving separate confirmatory factor
analyses using multiple homogenous patient populations. In the first
published reply to our study, Larrabee (2003)
pointed out other limitations, stating that application of factor-analytic
techniques to a single test that yields multiple measures may result in
global, simplistic solutions due to method variance, which is the tendency
of different variables from the same test to correlate significantly.