Theories and hypotheses: The forgotten plane of the multiverse

Multiverse analyses-the systematic examination of the effects of decisions that researchers can take over the course of a research project-became more common in recent psychophysiological research. However, multiverse analyses in psychophysiology almost exclusively focus on methodological and statistical decisions that can have a considerable impact on the findings. The role of the conceptual multiverse regarding theory-related research decisions is largely ignored. We argue that the choice of a theory that guides hypotheses, study design, measurement methods, and statistical analyses is the first plane of the psychophysiological multiverse. Depending on the chosen theoretical framework, researchers will choose different methods, and statistical analyses will emphasize specific aspects. We illustrate this process with a research example studying the effects of task difficulty manipulations on cardiovascular effects reflecting effort. We argue in favor of an approach that explicitly acknowledges the various theoretical accounts that can constitute the background of a study and demonstrate how a comparative analytical approach can provide a comprehensive multiverse without increasing type I error due to mere exploration.