My most recent post described the history of the periodic table in chemistry. Behavioral research today has problems similar to those faced by chemistry in the 1800s, with a need for (a) consistent classification of elements, (b) periodicity or the grouping together of related items, (c) underlying mechanisms that can explain the similarities among elements as well as their differences from one another, and (d) inter-relationships of the elements to one another. The periodic table accomplishes all of these things, and it doesn't have to be arranged into rows and columns to do it. Above is another alternate version of the periodic table that shows elements arranged in a circle, progressing clockwise outward from the center and showing groupings of related elements as colored rays. Behavioral science, though, is struggling with even the first of the periodic table's beneficial properties. Classification. It can be hard to get behavioral scientists even to agree on what we study....