Fig. 3. Three inferential problems that a single measure cannot resolve.
(A) Distinct processes can produce the same change in one measure while differing in their effects on others, so the observed change alone does not identify the process that generated it. (B) With additional dimensions, clusters can emerge that are not recoverable from any constituent measure on its own. (C) A multivariate Gaussian fit to the joint distribution of the collected measures (outline) provides a reference against which dynamic activity can be described with red arrows showing the direction of change. Such excursions may not be apparent in any single measure. All panels are schematics.