Incredible Utility: The Lost Causes and Causal Debris of Psychological Science

Abstract

Variable-oriented, sample-based individual differences research strategies and statistical modeling approaches to causal-theoretical inference depend on their logic, coherence, justification, and presumed heuristic value on the tacit assumption that individuals are qualitatively the same, homogeneous with respect to the psychological structures and processes underlying their overt functioning, and that quantitative differences between them are produced by exactly the same psychological structures functioning in exactly the same way within each individual. This psychological homogeneity assumption, however, is demonstrably false and invalidated by a substantial body of uncontested scientific evidence documenting psychological heterogeneity as a ubiquitous, defining characteristic of human functioning. This irreconcilable mismatch between the psychological homogeneity assumption of the paradigm and the psychologically heterogeneous realities of its phenomena renders the individual differences methodology intrinsically incapable of advancing theoretical knowledge about the causes of psychological and behavioral phenomena. A detailed look at this mismatch reveals also that it holds considerable explanatory power as the root cause of the slow theoretical progress and replication failures of psychological research, as well as the driving force behind psychology's inability to relinquish its controversial reliance on null hypothesis significance testing as a justification standard for evaluating theoretical claims.

Acknowledgments

I am indebted to Steve Hinshaw, Everett Waters, Hope N. Riley, Tim Brennan, Mike Maltz, and David Trafimow for their helpful feedback on earlier drafts of this paper. Reaching further back, I owe a special debt of gratitude to Paul Meehl, whose early encouragement, support, and guidance was indispensable to shaping the core arguments that eventually found their way into this paper. The initial scaffolding of the incredible utility thesis was forged in the crucible of an intensive dialogue with Paul that began in 1998 with a sequestered 5-hour meeting in his D.C. hotel room and continued over the next 18 months through ongoing email, fax, and audiotape communications. Immeasurably better than it would have been without Meehl’s early guidance, the final manuscript also falls far short of what it might have been had he survived through its completion. Finally, looking ahead and realizing that my thesis is a bitter pill to swallow, I’m grateful in advance to readers who resist the temptation to set it aside in favor of a critical evaluation of its supporting arguments.