The Psychology of Lumping and Splitting

The American playwright Tennessee Williams famously remarked, "There are only three great cities in the United States: New York, San Francisco, and New Orleans. Everything else is Cleveland."

Ouch. Clevelanders will undoubtedly feel aggrieved by this sentiment, as are the city-dwelling Americans from anywhere outside those allegedly elite three. No love for Chicago's skyline, Boston's Bay, or LA's Hollywood scene?

One could argue that Williams's elitism may be a bit extreme. But it illustrates a crucial feature of human perception: lumping and splitting.

Let's take cities as an example. For better or worse, we don't systematically evaluate each new city we visit. Each one isn't a blank canvas. Instead, we get off the plane full of prejudice and bias. And not just about the particular city we're visiting, but with a set of assumptions about cities in general.

These beliefs have gradually accumulated over a lifetime of visiting different cities. They've formed your basic expectations: There's probably a downtown area, some tall buildings, and some suburbs. Over time, you may even get a sense of familiarity in new cities you've never visited before.

Psychologists call this set of assumptions a schema: the general template, based on previous experience and knowledge, for this "category of experience." It's your brain's way of saying, "Oh yeah, we've been there before: here's the basic blueprint."

The existence of these schema gives our brain a choice with each new encounter: Do we "lump it" into an existing schema? Or do we "split it" into its own unique category of experience?

So what’s happening here? And how do these schemas shape our perception of the world?

Lumping, Splitting, and Perception

This mechanism of lumping and splitting isn't limited to cities and travel experiences but to all of our experiences and encounters.

For example, imagine going to a doctor's appointment. Even if it's a new doctor you've never met, in a hospital you've never been to, you still know, generally speaking, what to expect. You know you'll show up in a waiting room, check in with a receptionist, and then a tiny doctor's room where you'll finally get called into the doctor's office.

We engage in this process for all kinds of familiar events and scenarios. They help us navigate the world, and approach new situations with confidence and familiarity. If we've encountered something familiar in the past, we can use this general knowledge and avoid starting from scratch.

While lumping and splitting are an inherent part of human nature, they also divorce us from reality. As we'll soon see, they're a perceptual heuristic that builds our inner world, leading us to experience things that are not always reflected in the external world. And as we've seen with Tennessee Williams, they lead us to dismiss the juicy details and fine-grained nuances.

Before we can understand the implications of schemas in our everyday lives, let's first see how they work. What's the brain science that drives this process of lumping and splitting? Let's begin by looking at the broader process the brain is constantly engaged with: perceptual assumptions.

Lumping, Splitting, and Perceptual Assumptions

To fully appreciate lumping and splitting, we first have to recognize that the outside world is hectic. We're constantly bombarded with an overwhelming amount of sensory data. The full richness of the visual world, the constant vibrations hitting our ears, and all the smells, tastes, and tactile sensations that follow us everywhere we go.

Even if we wanted to, we couldn't process all of this. So how do we cope with this complexity?

Our brain, largely outside of our awareness, makes perceptual assumptions about what it thinks is out there. This general process is known as top-down processing, or "filling in." So while the outside world is busy, it doesn't seem busy.

Most of the time, we never notice this "filling in" process. We just go on, looking around and experiencing the world and assuming that's the way the world is. But in fact, it's a simplified model of the world that our brain has built based mostly on its own assumptions.

One of the most prominent examples of this is the visual blind spot. At the point where your optic nerve meets the retina, roughly 15 degrees from your center of vision, you're not getting any visual information. This is the blindspot, and we have one in each of our eyes. But despite this fact of our biology, you've likely never noticed this.

Part of this comes down to having two eyes with overlapping fields of vision: what one eye misses, the other can compensate. But of course, when you cover one eye, you don't immediately see a massive black patch in your visual field. This is because your brain is constantly "filling in." It's continuously processing only a small amount of the visual scene, assuming the rest.

Perceptual assumptions are a fundamental feature of how we experience the world. We ultimately perceive an experiential cocktail: one part real-world sensory data, two parts assumption.

From Lumping and Splitting to Perception and Memory

There's a direct line from perceptual "filling in" to the formation of these psychological schemas, and in turn to this process of lumping and splitting.

Our brain simplifies the perceptual world by making intelligent assumptions about it. We do something very similar for events and experiences—anything from going to the doctor, to going on vacation to somewhere new. Think of it like "filling in," but applied to life events. We don't take in the event as it is, but as it thinks it should experience it.

These schemas follow us everywhere we go. They influence not just what we perceive in the moment, but what we remember about the experience. For example, if we hear a new story, we typically remember what we think we should have heard, instead of the actual, specific details of the event. As a result, we're likely to neglect, forget, or misremember aspects that don't fit our predetermined expectations.

In a classic study examining the impact of schema on memory, participants were brought into an office and told simply to sit and wait for further instruction. That's it, no directions or tasks. After half a minute, the participants were brought out and asked to list as many objects from the room as possible.

Overwhelmingly, participants could accurately recall the objects that fit into the general schema of "office room"—objects like desks, chairs, picture frames, staplers, etc. However, they exhibited immense difficulty recalling things like an artifact of a skull, or a tea kettle, which didn't readily fit in. If they can't be "lumped" they can't easily be remembered as part of that lump.

Schemas also lead us to generate memories of things that didn't even happen. One of the most interesting findings was that participants reliably remembered seeing books in the office, which fit well with the "office room" schema, despite the fact that there weren't any there. In this way, false memories are often the result of a pre-existing schema.

Schemas, Lumping, and Splitting

Ultimately, lumping and splitting is about the perception of novelty. In any given experience or encounter, the brain's task is simple: It asks, is this a familiar thing? If so, we can lump it in with an existing schema.

This is what Tennessee Williams did with cities not named New York, New Orleans, or San Francisco. Every other city is lumped in with the general schema of the blasé American city (e.g., Cleveland).

But if this thing doesn't appear familiar, it's because there isn't an existing schema for it. In this case, it's categorized as a distinct experience all on its own. We split it off from the rest of our understanding of the world. It's special. In the Tennessee Williams example, this would be the rarified three cities that stand independently.

Is one way of perceiving the world “better” than the other? Schemas are part of human nature, and each has its strengths and weaknesses: Lumping allows us to approach new experiences with familiarity and confidence, but collapses the details. Splitting leads us to see these fine-grained nuances, but does not provide anything about how to act or think about these completely novel scenarios.

Each of us has our own tendencies when it comes to schemas. Francis Bacon said it best when he remarked, "Some minds are stronger and apter to mark the differences of things, others to mark their resemblances." If there's any "best" system, it may be to build awareness of our own schematic tendencies. With this self-awareness, we may be able to wield the power of schemas to their greatest benefit—harnessing its confidence from “lumping" and enjoying the nuances that “splitting” provides.

And in this way, even Cleveland may have its own charm.

This post also appears on the Human Nature Blog, Neuroscience Of.

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