What is specification error in research?

With some degree of regularity I find myself having to explain how model "specification error" can distort research findings, especially studies that use predictive (multiple regression, causal modeling). So, below is a definition with an analogy from a 2005 publication. This is one of the most series problem with many research studies that claim to have identified THE important predictors of some dependent variable (e.g, reading disability research)

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