Reassessing the Metrics of Integration: Toward Eliminating the Blur between Theory and Statistics to Clarify Effect Sizes, Measurement, and Causality in Acculturation Psychology

The debate around the integration hypothesis in acculturation research often hinges on the interpretation of effect sizes. Critics label these effects as too small and inconsistent, questioning their significance, while supporters argue they are robust enough to validate the hypothesis. This controversy underscores a broader challenge and widespread misunderstanding among psychologists regarding the philosophical basis of measurement and causality, specifically the vague criteria for what constitutes a ‘sufficient’ effect size. The ambiguity may arise from the field’s limited focus (characteristic of psychology in general) on the issues of measurement, and is compounded by the common ‘ergodic fallacy,’ which mistakenly applies group level characteristics to individuals. This paper addresses these issues through three main discussions. Firstly, it evaluates the ongoing debate on the integration hypothesis in light of recent meta-analyses. Secondly, it analyzes how effect sizes should be attributed—whether to populations, samples, or individuals—and establishes criteria for assessing their significance. Lastly, it examines the philosophical underpinnings of measurement in psychology and causality. By exploring these areas, the paper aims to clarify and enhance the coherence of discussions on effect sizes, measurement, and causality in acculturation research.