Only time will tell: cross-sectional studies offer no solution to the age-brain-cognition triangle: comment on Salthouse (2011).

Salthouse (2011) critically reviewed cross-sectional and longitudinal relations among adult age, brain structure, and cognition (ABC) and identified problems in interpretation of the extant literature. His review, however, missed several important points. First, there is enough disparity among the measures of brain structure and cognitive performance to question the uniformity of B and C vertices of the ABC triangle. Second, age differences and age changes in brain and cognition are often nonlinear. Third, variances and correlations among measures of brain and cognition frequently vary with age. Fourth, cross-sectional comparisons among competing models of ABC associations cannot disambiguate competing hypotheses about the structure and the range of directed and reciprocal relations between changes in brain and behavior. We offer the following conclusions, based on these observations. First, individual differences among younger adults are not useful for understanding the aging of brain and behavior. Second, only multivariate longitudinal studies, age-comparative experimental interventions, and a combination of the two will deliver us from the predicaments of the ABC triangle described by Salthouse. Mediation models of cross-sectional data represent age-related differences in target variables but fail to approximate time-dependent relations; thus, they do not elucidate the dimensions and dynamics of cognitive aging.

[1]  R. Cattell,et al.  Age differences in fluid and crystallized intelligence. , 1967, Acta psychologica.

[2]  R Kliegl,et al.  Speed and intelligence in old age. , 1993, Psychology and aging.

[3]  P. Rabbitt,et al.  Does it All Go Together When it Goes? The Nineteenth Bartlett Memorial Lecture , 1993, The Quarterly journal of experimental psychology. A, Human experimental psychology.

[4]  T A Salthouse.  Constraints on theories of cognitive aging , 1996, Psychonomic bulletin & review.

[5]  Paul B. Baltes,et al.  Intellectual Development in Adulthood: The Seattle Longitudinal Study , 1996 .

[6]  P. Baltes,et al.  Emergence of a powerful connection between sensory and cognitive functions across the adult life span: a new window to the study of cognitive aging? , 1997, Psychology and aging.

[7]  Faith M. Gunning-Dixon,et al.  Neuroanatomical correlates of cognitive aging: evidence from structural magnetic resonance imaging. , 1998, Neuropsychology.

[8]  T. Little,et al.  On selecting indicators for multivariate measurement and modeling with latent variables: When "good" indicators are bad and "bad" indicators are good. , 1999 .

[9]  N. Raz.  Aging of the brain and its impact on cognitive performance: Integration of structural and functional findings. , 2000 .

[10]  Reese Baltes.  The Complex Nature of Unique and Shared Effects in Hierarchical Linear Regression : Implications for Developmental Psychology , 2001 .

[11]  D. Stuss,et al.  Principles of frontal lobe function , 2002 .

[12]  D. Salat,et al.  Greater orbital prefrontal volume selectively predicts worse working memory performance in older adults. , 2002, Cerebral cortex.

[13]  Ulman Lindenberger,et al.  Longitudinal selectivity in aging populations: separating mortality-associated versus experimental components in the Berlin Aging Study (BASE). , 2002, The journals of gerontology. Series B, Psychological sciences and social sciences.

[14]  J. Gabrieli,et al.  Insights into the ageing mind: a view from cognitive neuroscience , 2004, Nature Reviews Neuroscience.

[15]  L. Nyberg,et al.  Betula: A Prospective Cohort Study on Memory, Health and Aging , 2004 .

[16]  E. Plante,et al.  Memory and executive function in older adults: relationships with temporal and prefrontal gray matter volumes and white matter hyperintensities , 2004, Neuropsychologia.

[17]  N. Raz,et al.  Shrinkage of the Entorhinal Cortex over Five Years Predicts Memory Performance in Healthy Adults , 2004, The Journal of Neuroscience.

[18]  C. Petten.  Relationship between hippocampal volume and memory ability in healthy individuals across the lifespan: review and meta-analysis , 2004, Neuropsychologia.

[19]  C. Van Petten,et al.  Relationship between hippocampal volume and memory ability in healthy individuals across the lifespan: review and meta-analysis. , 2004, Neuropsychologia.

[20]  P. Diggle,et al.  Practice and drop-out effects during a 17-year longitudinal study of cognitive aging. , 2004, The journals of gerontology. Series B, Psychological sciences and social sciences.

[21]  L. Nyberg,et al.  Stability, growth, and decline in adult life span development of declarative memory: cross-sectional and longitudinal data from a population-based study. , 2005, Psychology and aging.

[22]  Cheryl L. Dahle,et al.  Regional brain changes in aging healthy adults: general trends, individual differences and modifiers. , 2005, Cerebral cortex.

[23]  L. Collins.  Analysis of longitudinal data: the integration of theoretical model, temporal design, and statistical model. , 2006, Annual review of psychology.

[24]  U. Lindenberger,et al.  On the power of multivariate latent growth curve models to detect correlated change. , 2006, Psychological methods.

[25]  G J Blauw,et al.  Measuring longitudinal white matter changes: comparison of a visual rating scale with a volumetric measurement. , 2006, AJNR. American journal of neuroradiology.

[26]  Brian P. Flaherty,et al.  Cross-Sectional Analysis of Time-Dependent Data: Mean-Induced Association in Age-Heterogeneous Samples and an Alternative Method Based on Sequential Narrow Age-Cohort Samples , 2006, Multivariate behavioral research.

[27]  C. Büchel,et al.  Temporal and Spatial Dynamics of Brain Structure Changes during Extensive Learning , 2006, The Journal of Neuroscience.

[28]  S. Maxwell,et al.  Bias in cross-sectional analyses of longitudinal mediation. , 2007, Psychological methods.

[29]  Cindy M. de Frias,et al.  Intraindividual variability in neurocognitive speed: A comparison of Parkinson's disease and normal older adults , 2007, Neuropsychologia.

[30]  Cindy M. de Frias,et al.  Revisiting the dedifferentiation hypothesis with longitudinal multi-cohort data. , 2007 .

[31]  Ulman Lindenberger,et al.  Evaluating the Power of Latent Growth Curve Models to Detect Individual Differences in Change , 2008 .

[32]  U. Lindenberger,et al.  Neuroanatomical correlates of fluid intelligence in healthy adults and persons with vascular risk factors. , 2008, Cerebral cortex.

[33]  A. Kramer,et al.  Enrichment Effects on Adult Cognitive Development , 2008, Psychological science in the public interest : a journal of the American Psychological Society.

[34]  W. Johnson,et al.  Handbook of Aging and Cognition , 2008 .

[35]  T. Salthouse.  When does age-related cognitive decline begin? , 2009, Neurobiology of Aging.

[36]  L. Nyberg,et al.  Challenging the notion of an early-onset of cognitive decline , 2009, Neurobiology of Aging.

[37]  Arthur F. Kramer,et al.  Age-related differences in regional brain volumes: A comparison of optimized voxel-based morphometry to manual volumetry , 2009, Neurobiology of Aging.

[38]  Ulman Lindenberger,et al.  On the relation of mean reaction time and intraindividual reaction time variability. , 2009, Psychology and aging.

[39]  J. Mcardle.  Latent variable modeling of differences and changes with longitudinal data. , 2009, Annual review of psychology.

[40]  Mark D'Esposito,et al.  Imaging the aging brain , 2009 .

[41]  Steven M Boker,et al.  Issues in intraindividual variability: individual differences in equilibria and dynamics over multiple time scales. , 2009, Psychology and aging.

[42]  A. Dale,et al.  Distinct genetic influences on cortical surface area and cortical thickness. , 2009, Cerebral cortex.

[43]  U. Lindenberger,et al.  Cognitive and sensory declines in old age: gauging the evidence for a common cause. , 2009, Psychology and aging.

[44]  T. Salthouse.  Does the meaning of neurocognitive change change with age? , 2010, Neuropsychology.

[45]  Ayanna K. Thomas,et al.  Theoretical Perspectives on Cognitive Aging , 2019, Handbook of Medical Neuropsychology.

[46]  L. Keele,et al.  A General Approach to Causal Mediation Analysis , 2010, Psychological methods.

[47]  Ulman Lindenberger,et al.  The effect of multiple indicators on the power to detect inter-individual differences in change. , 2010, The British journal of mathematical and statistical psychology.

[48]  M. Andersson,et al.  Longitudinal evidence for diminished frontal cortex function in aging , 2010, Proceedings of the National Academy of Sciences.

[49]  Vince D. Calhoun,et al.  Age-Related Changes in Processing Speed: Unique Contributions of Cerebellar and Prefrontal Cortex , 2010, Front. Hum. Neurosci..

[50]  Ulman Lindenberger,et al.  Trajectories of brain aging in middle-aged and older adults: Regional and individual differences , 2010, NeuroImage.

[51]  Hans-Jochen Heinze,et al.  Experience-dependent plasticity of white-matter microstructure extends into old age , 2010, Neuropsychologia.

[52]  T. Salthouse.  Influence of age on practice effects in longitudinal neurocognitive change. , 2010, Neuropsychology.

[53]  David H. Salat,et al.  Cognition in healthy aging is related to regional white matter integrity, but not cortical thickness , 2010, Neurobiology of Aging.

[54]  Nicolas Cherbuin,et al.  Relationships between cognitive function and frontal grey matter volumes and thickness in middle aged and early old-aged adults: The PATH Through Life Study , 2011, NeuroImage.

[55]  T. Salthouse.  Neuroanatomical substrates of age-related cognitive decline. , 2011, Psychological bulletin.

[56]  R. Dixon,et al.  Tracking cognition-health changes from 55 to 95 years of age. , 2011, The journals of gerontology. Series B, Psychological sciences and social sciences.

[57]  U. Lindenberger,et al.  Cross-sectional age variance extraction: what's change got to do with it? , 2011, Psychology and aging.

[58]  A. Meyer-Lindenberg,et al.  Normal age-related brain morphometric changes: nonuniformity across cortical thickness, surface area and gray matter volume? , 2012, Neurobiology of Aging.

[59]  Irene E. Nagel,et al.  Cortical thickness is linked to executive functioning in adulthood and aging , 2012, Human brain mapping.

[60]  Hans-Jochen Heinze,et al.  Spatial navigation training protects the hippocampus against age-related changes during early and late adulthood , 2012, Neurobiology of Aging.

[61]  Ulman Lindenberger,et al.  Heterogeneity in frontal lobe aging , 2013 .

[62]  T. Salthouse,et al.  Constraints on theories of cognitive aging , 1996, Psychonomic bulletin & review.