Correlations in Social Neuroscience Aren't Voodoo. Lieberman, M. D, Berkman, E. T, & Wager, T. D Perspectives on Psychological Science, 4(3):299–307, 2009.
abstract   bibtex   
Vul, Harris, Winkielman, and Pashler (2009, this issue) claim that many brain–personality correlations in fMRI studies are ‘‘likely . . . spurious’’ (p. 274), and ‘‘should not be believed’’ (p. 285). Several of their con- clusions are incorrect. First, they incorrectly claim that whole-brain regressions use an invalid and ‘‘nonindepen- dent’’ two-step inferential procedure, a determination based on a survey sent to researchers that only included nondiagnostic questions about the descriptive process of plotting one’s data. We explain how whole-brain regres- sions are a valid single-step method of identifying brain regions that have reliable correlations with individual difference measures. Second, they claim that large corre- lations from whole-brain regression analyses may be the result of noise alone. We provide a simulation to demon- strate that typical fMRI sample sizes will only rarely produce large correlations in the absence of any true ef- fect. Third, they claim that the reported correlations are inflated to the point of being ‘‘implausibly high.’’ Though biased post hoc correlation estimates are a well-known consequence of conducting multiple tests, Vul et al. make inaccurate assumptions when estimating the theoretical ceiling of such correlations. Moreover, their own ‘‘meta- analysis’’ suggests that the magnitude of the bias is ap- proximately .12—a rather modest bias.
@article{lieberman_correlations_2009,
	title = {Correlations in {Social} {Neuroscience} {Aren}'t {Voodoo}},
	volume = {4},
	abstract = {Vul, Harris, Winkielman, and Pashler (2009, this issue) claim that many brain–personality correlations in fMRI studies are ‘‘likely . . . spurious’’ (p. 274), and ‘‘should not be believed’’ (p. 285). Several of their con- clusions are incorrect. First, they incorrectly claim that whole-brain regressions use an invalid and ‘‘nonindepen- dent’’ two-step inferential procedure, a determination based on a survey sent to researchers that only included nondiagnostic questions about the descriptive process of plotting one’s data. We explain how whole-brain regres- sions are a valid single-step method of identifying brain regions that have reliable correlations with individual difference measures. Second, they claim that large corre- lations from whole-brain regression analyses may be the result of noise alone. We provide a simulation to demon- strate that typical fMRI sample sizes will only rarely produce large correlations in the absence of any true ef- fect. Third, they claim that the reported correlations are inflated to the point of being ‘‘implausibly high.’’ Though biased post hoc correlation estimates are a well-known consequence of conducting multiple tests, Vul et al. make inaccurate assumptions when estimating the theoretical ceiling of such correlations. Moreover, their own ‘‘meta- analysis’’ suggests that the magnitude of the bias is ap- proximately .12—a rather modest bias.},
	number = {3},
	journal = {Perspectives on Psychological Science},
	author = {Lieberman, Matthew D and Berkman, Elliot T and Wager, Tor D},
	year = {2009},
	pages = {299--307},
}

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