At this juncture in our field, constant centrifugal forces pressure us to fly apart at the seams, breaking psychology apart. The forces are visible everywhere in the challenges they present:
- Splitting psychology into separate departments, resulting in a number of bad divorces or enduring but unhappy marriages across research areas
- Maintaining balance and broad commitment in our whole-field journals, such as Psychological Science, Current Directions in Psychological Science, and Psychological Science in the Public Interest
- Exposing students adequately to all of psychology in a single survey course
- Representing psychology in the Annual Review series, concurrent with more specialized companion volumes, such as Neuroscience
- Keeping trust and loyalty across constituencies within our whole-field organizations, such as APS.
In this context of splitting forces, which operate in the service of bright but narrow intellectual focus, organizations such as APS have a crucial role in keeping us all together. APS is the one organization where scientific psychologists – and only scientific psychologists – come together for cross-talk. All this forms temporary kinds of intellectual bridges. From APS activities (conventions, journals, committees), people get to know each other across boundaries. This forms more permanent kinds of intellectual bridges: The individual scientists and collaborative teams who venture across boundaries for a longer stay. These cross-area efforts glue us together as a discipline, a nontrivial scientific contribution.
What motivates people to bridge boundaries or not, and how to they do it? Some people say there are two kinds of psychological scientists: lumpers and splitters. Lumpers like to synthesize apparent differences under a few overarching principles, seeking similarities. Splitters like to analyze precise distinctions, dealing in differences.
Other people say there are another two kinds of psychological scientists: Neats and Scruffies : Scruffies want to be interesting and take big leaps, even at the risk of being wrong and changing their minds (perhaps in midair). Neats want to be right, even at the risk of taking overly cautious incremental steps, building science one brick at a time.
I suspect these modes of science are correlated. Probably, lumpers tend to be scruffy, and splitters tend to be neat.  I will argue, however, that it ain’t necessarily so. Some combination is beneficial: Psychological science finds some of its best insights in lumping – neatly. What I have in mind is the hyphenated research that finds similarities in problems investigated in seemingly different areas and sub-areas, and builds bridges of methods and theories to link the two. Finding common cause in apparently disparate domains requires a kind of mental lumping, but it is of course best done with considerable attention to neatness. This is the best kind of glue.
This year’s presidential columns will highlight some illustrative bridge areas in current psychological science, efforts that operate at the boundaries between psychology’s subdisciplines and between psychology and other disciplines. Among the bridging sub-disciplines now lumping neatly are cognitive neuroscience and social neuroscience, which are producing fascinating work at an astounding rate. Among the subdisciplines that have happily hyphenated for a longer time are behavior genetics, psychophysiology, social cognition, social-personality psychology, cognitive development, developmental psychobiology, and clinical neuropsychology. Among the hyphenated subdisciplines that collaborate outside of psychology are new efforts in neuro-economics, as well as continuing work in political, health, legal, cultural, and evolutionary psychology.
Key challenges confront psychological scientists who bridge boundaries. They typically start from a home area and bridge to a new area. The homies may view them as disloyal deserters. The new area may view them as alien invaders. So they are caught in between, fully adopted by no camp. This ramifies to resources, alliances, and identity.
If they bridge from a more micro (biological, mathematical, or physical) home science to a more macro (social, clinical, or developmental) new science, their old colleagues scorn them for going soft in the head, being less rigorous, more scruffy, and too sloppy. Their new, would-be colleagues may resent their efforts as arrogant and ignorant. If they bridge from home macro to new micro, the perceptions reverse. Essentially, of course, this is about status asymmetries, but knowing that doesn’t make the problem go away.
The problems of expertise are real. All the material learned in graduate school and beyond – methods, literature, theoretical styles – are missing for the person expert in another area but neophyte in a new one. What to do?
Collaborations cure some of these problems. A willingness to admit ignorance and to a willingness to tolerate naiveté together cure some. Subscribing less strictly to micro-macro (or hard-soft) hierarchies cures others. A genuine curiosity about what makes people tick, and doing whatever it takes to find out, got all of us into this business in the first place. It is well to remember the common goal.
Lumpers and bridgers could be accused of having carpet-sweeper minds, gathering together dusty discarded bits and pieces, but observers have to admit that it leaves the place neater than it began. Many of the bridgers are taking their lumps, but they like it and lump it anyway. Consider these preliminary thoughts as highlights for now; complete stories follow in later editions. Meanwhile, stay tuned to APS for some great excursions across boundaries.
2. I leave it to philosophers and historians of science to provide the derivations of these now-common distinctions, and I leave it to our colleagues in personality and individual differences to devise the appropriate psychometrics.