Since all models are wrong the scientist cannot obtain a “correct” one by excessive elaboration. On the contrary following William of Occam he should seek an economical description of natural phenomena. Just as the ability to devise simple but evocative models is the signature of the great scientist so overelaboration and overparameterization is often the mark of mediocrity.

-George Box (1976)

Positive manifold refers to the empirical observation that scores on diverse cognitive tasks are positively correlated, albeit to varying degrees depending on the measures involved. Despite being a robust phenomenon, this observation has led to one of the most vexing debates in all of psychology. Whereas some psychologists (e.g., Bartholomew, 2004; Jensen, 1998; Spearman, 1904) accept these correlations as prima facie evidence for the existence of a latent general intelligence factor or g, others suggest that positive manifold is reductionist and that the resulting g factor is nothing more than a statistical artifact (Horn & Blankson, 2005; Thompson, 1951; Thurstone, 1938). Although many methodological and theoretical advances have been made over the last century, many questions remain about the structure of intellectual functioning and relationships between cognitive abilities and external criterion. How do we define and operationalize theoretical models of human cognitive abilities and what are the potential implications of these models with respect to applied psychological assessment (e.g., identifying specific learning disability and other forms of psycho-social impairment)? How do we design measurement instruments and ultimately assess more discrete cognitive abilities with enough unique variance to distinguish these indicators from g (even if it represents a statistical artifact)? How do we distinguish between psuedoscience and science (e.g., Lilienfeld, Ammirati, & David, 2012) and ultimately incorporate evidence-based interpretive methods when appraising these abilities? These are just some of the questions that continue to fascinate me and serve as the basis for my scholarship.

Different models representing the latent structure of a commercial ability measure.

This purpose of this site is to serve as an online repository for my scholarly work as well as to document the evolution of my research interests. It is my goal for this site to serve as an extension of my scholarship as a public intellectual within the tradition of the Boyer model (Boyer, 1990). Debates on these matters can quickly lead to ideological disagreements. In spite of this, I believe these discussions are important not only for school psychology but psychology in general. Thus, they serve as a major focus of my scholarly agenda.

The content herein is my own is not in any sense endorsed by either William & Mary in general or the Department of School Psychology and Counselor Education in particular.


Bartholomew, D. J. (2004). Measuring intelligence: Facts and fallacies. Cambridge University Press.

Box, G. E. P. (1976). Science and statistics. Journal of the American Statistical Association, 71(356), 791-799.

Boyer, E. L. (1990). Scholarship reconsidered: Priorities of the professoriate. Carnegie Foundation for the Advancement of Teaching.

Horn, J. L., & Blankson, N. (2005). Foundations for better understanding of cognitive abilities. In D. P. Flanagan, & P. L. Harrison (Eds.), Contemporary intellectual assessment: Theories, tests, & issues (pp. 41-68, 2nd ed.). Guilford Press.

Jensen, A. R. (1998). The g factor: The science of mental ability. Praeger.

Lilienfeld, S. O., Ammirati, R., & David, M. (2012). Distinguishing science from pseudoscience in school psychology: Science and scientific thinking as safeguards against human error. Journal of School Psychology, 50(1), 7-36.

Spearman, C. (1904). “General intelligence,” objectively determined and measured. American Journal of Psychology, 15(2), 201-293.

Thompson, G. (1951). The factorial analysis of human ability (5th ed.). University of London Press.

Thurstone, L. L. (1938). Primary mental abilities. University of Chicago Press.