Latent Variable Modeling of Cognitive Reserve Richard N. Jones, Sc.D. Friday Harbor Advanced Psychometrics Workshop 2009

Acknowledgements Funded in part by Grant R13AG A1 from the National Institute on Aging The views expressed in written conference materials or publications and by speakers and moderators do not necessarily reflect the official policies of the Department of Health and Human Services; nor does mention by trade names, commercial practices, or organizations imply endorsement by the U.S. Government.

Overview What is a latent variable? What is cognitive reserve? How has reserve been approached as a latent variable? Formative vs. Reflective Measurement of latent variables Opportunities for cognitive reserve

Latent Variables …Other times latent variables may not be physically real but instead correspond to abstract concepts, like categories, behavioral or mental states, or data structures. The terms hypothetical variables or hypothetical constructs may be used in these situations.

Borsboom, Mellenbergh et al., The theoretical status of latent variables Psychol Rev 110: Theoretical Status of Latent Variables

Three Ontological Positions Realism. The latent variable exists independent of measurement –Electrons prior to 1897, Dark matter/energy nowadays –Francis Galton’s view of intelligence Constructivist. The latent variable is a construction of the human mind –Gould’s view on intelligence Operationalist/Instrumentalist. The latent variable is nothing more than a (useful?) mathematical abstraction. –A kind of constructivist position, broader and empirically based –Gould’s view on IQ Borsboom, Mellenbergh et al., 2003 Psychol Rev 110: Gould SJ. The Mismeasure of Man

Cognitive Reserve Let’s assume CR is a hypothetical construct, a latent variable. –It’s not directly observed, since we’re not even sure what it is (or if it even exists) Something that encompasses the quantity, efficiency, and flexibility of the brain (neurons, networks)

Proxies for Reserve Valenzuela and Sachdev, 2006 Psychol Med 36: Valenzuela and Sachdev, 2006 Psychol Med 36: In Re: Cognitive decline - sometimes (e.g., Christensen, Hofer et al., 2001 Psychol Med 31:15-28) tests like the NART used as an outcome measure.

Borsboom, Mellenbergh et al., The theoretical status of latent variables Psychol Rev 110: Borsboom’s Questions

Formative and Reflective Measurement Borsboom, Mellenbergh et al., 2003 Psychol Rev 110:203-18

Formative and Reflective Measurement Borsboom, Mellenbergh et al., 2003 Psychol Rev 110: Reflective Measurement The latent trait (  ) causes the observed responses (x) The latent trait is reflected by observed responses People with high IQ articulate e = mc 2

Formative and Reflective Measurement Borsboom, Mellenbergh et al., 2003 Psychol Rev 110: Formative Measurement The latent trait (  ) is caused (formed) by the observed responses (x) e.g., SES (  ) changes as a result of increase in salary (x)

Siedlecki, Stern et al., 2009 J Int Neuropsychol Soc 15: PPVT - Picture Vocabulary Test WRAT/WAT - Performance on the reading subtest of either the WRAT or the WAT. Each of these variables presumably reflects life experiences, above and beyond that of age, that have the po- tential to provide protection against Clinical manifestation of disease in the brain and has been used in the literature as a proxy for cognitive reserve. See also Scarmeas, Zarahn et al., 2004 Arch Neurol 61:73-8

Mueller and Parcel. Measures of socioeconomic status: Alternatives and recommendations Child Dev 52:13-30

Formative Measurement

Formative Measurement Trick

Formative Measurement

Potential Applications in MAP and other possible workshop goals

Thinking->Opining about Cognitive Reserve as a LV Of the various suggested proxies for reserve… –which are formative? –which are reflective? How can they be meaningfully and appropriately included together in data analysis? How do background factors influence aspects of formative and reflective measurement? –sex, race, ethnicity, country of origin (education), language, etc.

A Lifecourse Perspective on Reserve may help guide Thinking Richards and Deary, 2005 Annals of Neurology 58:617-22

Modeling a Lifecourse Perspective on Reserve Richards and Sacker, 2003 J Clin Exp Neuropsychol 25:614

Applications in MAP

Why not a Latent Class Model? Borsboom, Mellenbergh et al., The theoretical status of latent variables Psychol Rev 110:203-18