A Psychological Analysis of Strangers and Hospitality, Part 3: Hospitality and Our Moral Bandwidth


When you get right down to it, that's the problem.


One of the most famous papers in cognitive psychology is George Miller's paper concerning the capacity of short-term memory. The paper was entitled The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information. Miller's research was important in establishing the capacity or bandwidth of short-term memory. We can hold about seven (plus or minus two) pieces of information in short-term memory without any mnemonic device. About the length of a phone number. Most people given a phone number can hold it in memory and repeat it back. Past 10 digits you start seeing significant memory errors.

I'd like to use The Magical Number Seven to suggest that diverse lines of research are converging upon a different kind of magic number. This number seems to be associated with our moral capacity, our moral bandwidth. It is the number that identifies the number of people we tend to count as "family and friends," the people I pull out from the world of "strangers" as worthy of altruistic attention. This Magical Moral Number isn't seven. The Magical Moral Number appears to be around 150.

How are psychologists coming up with this number? Well, to begin, if the brain has an adaptive history we can expect the information-processing faculties of the brain to display certain biases associated with the adaptive challenges the brain faced during that history. Adaptive pressures tend to produce conservative solutions in organisms. Take memory again as an example. For whatever reason the brain didn't invest massive amounts into short-term memory. Apparently, long-term memory was more important that short-term memory. Which makes sense. So the brain is like an investment banker, it has finite resources and has to allocate them according to adaptive need. It is true that these investments can be changed through experiences. The left hand of an expert guitar player has more neurons devoted to it than do non-guitar players. Experience does rewire the brain. But this plasticity isn't infinite in scope. There are constraints. You don't want the brain taking away connections from, let's say, the neurons controlling your heartrate.

When it comes to our innate moral psychology we see something similar to what we observed with memory. Upon birth and throughout development the brain needs to be able to identify and recognize the people inhabiting its social world. We saw this in the last post. The brain carves the world into "family and friends" versus "strangers." The question is how big can the "family and friends" group get?

Given that the brain spent most of its adaptive history in small, kin-related hunting-gathering bands it seems reasonable that the brain, like with short term memory, would not devote infinite memory resources to keep track of all social relations. It seems reasonable to expect that the brain would allocate memory resources to the social faculty of the brain that roughly correlated with the size of these hunting-gathering bands. There would be no real need for the brain to devote memory resources past this point. Thus, it is argued, the brain developed a moral/social bandwidth, it has a natural limit to how large the family/friends group will be. The limit roughly correlates with the actual size the family/friend group found during most of the brain's adaptive history. And how big were those hunting-gathering bands? Most anthropologists have it around 150.

This number grows more intriguing given the following:

If we correlate size of neocortex and social group size in the animal kingdom we find a regular positive trend: As group size grows so does neocortex. You need more brain to remember agents in your social groups as well as a memory for all the "relationships" in the group (who hates who, etc.). For primates like chimps the group size is 55. Extrapolating from human cortical size our social groups should be...you guessed it...150.

The average of number of Christmas card lists tends to be around 150.

The average number of entries on personal address books is around 150.

Organizations under 150 can be managed via face to face interactions without creating an organizational hierarchy.

The size of a military company, the basic military unit, where face-to-face command and communication is used, is between 75 and 200.

The point is, humans appear to have a social and moral bandwidth of about 150. Our memories can keep track of groups about this size. Beyond it our interactions become more anonymous. Past a group size of 150 we start needing formal organizational structures to handle interactions. Further, the group we consider "friends and family" clusters around this size.

So our brains have a natural moral capacity of 150. Given the Christian call live in a world without strangers this creates a bit of a bandwidth problem. We are constantly fighting an inclination to focus our love and welcome to a group of 150.

This situation creates a lot of problems in the church. Preachers find it very hard to get people to care about more than 150 people. Plus, once those clusters get set up its hard to break into someone's tribe. Humans are naturally cliquey. Churches around 150 can function as one large family. Past 150 the church will have cliques.

Further, as we make calls for social justice it is hard to mobilize congregations to care about people worlds away. The appeals have to be pretty emotional and impactful to get our attention. This is difficult to do on a regular basis. Thus commitment to the poor waxes and wanes.

What can we do to combat this inclination? Well, here is a humble start. We need to practice what I'll call the rituals of hospitality in everyday life. Most of the people we encounter during the day will be strangers, they will be outside my 150 group. Consequently, I need to cultivate practices of welcome, greeting, kindness, fairness, humility, grace, and openness (among others) to have this interaction be deeply human and humane. I'm probably not going to be best friends with the girl taking my order at McDonald's but I can do everything in my power to treat her as a sister and a friend. I can refuse to dehumanize her. I can look her in the eye. I can smile. I can treat her mistakes with humor and compassion. I can compliment. I can be patient. I can personalize an impersonal interaction.

This is why I think hospitality is so important. It gives us rituals of social interaction that allow us to extend our moral bandwidth to the whole world.

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6 thoughts on “A Psychological Analysis of Strangers and Hospitality, Part 3: Hospitality and Our Moral Bandwidth”

  1. Dr. Beck,

    What's wrong with 150? Operating under the banner "act locally, think globally", it would seem that 150 is a big enough pallet to bear witness to. Given the option between broadening one's sphere of influence, and living authentically within one's influence, I would choose the latter. But then again, I'm a fan of the Polis that maxes out around 5,000 anyway. I can understand the problem in your context as a professor who must deal with a constantly changing community, but it still seems to me that the problem is not the number of associations, but the type of commitments we have with those of associations. With the McDonalds scenario, would it not be better to obtain our sustenance from exchanges of the personal instead of a facade of the personal that our brain does not have enough bandwith to make good on? I don't miss the irony of this being my first post to an author whom I have not met. That seems rife with implications as well.

  2. Hi Bryce,
    I appreciate the questions.

    First, as finite creature I agree that at some point I reach my limits as to having and investing in quality relationships. But my post raises the question: 150 may be an arbitrary limit set by the contingency of adaptive history. Like with the use of mnemonic devices our short-term memory can be manipulated to take in more than seven pieces of information. I'm wondering, first of all, if our moral focus might be able to expand if we wouldn't settle for what our biological inclinations settle for. Maybe our hearts have more room.

    Regardless, my example about the McDonald's encounter is to highlight how, given the psychology I describe, there are qualitative differences in how we treat "strangers." People beyond my "group" are, essentially, treated like ciphers. In traffic, in a line, across a counter, passing on the street, humans become so much furniture and backdrop to my real world, the 150 or so people I know by name and care about. True, as you point out, I can't make everyone I meet a best friend but we can resist treating them like social furniture, we can practice acts of personalization. This, I think, accomplishes three things:

    1) Fights against the dehumanization and passive acts of violence inherent in urban environments and in a market-driven world.

    2) Fights against the numbing of empathy in my own heart.

    3) Opens up the possibility of true friendship emerging. True, it's not likely that the McDonald's employee will enter my social circle but it is not impossible (see the book The Same Kind of Different as Me). But that possibility only opens up if I take up the task of not treating the McDonald's person as a cipher in my world. That's a part of what I'm getting at.

  3. This is interesting and entirely new to me - thanks for writing about it.

    Certainly I think we should be trying to expand the numbers of people we can genuinely care for. But if it's true that friendship is not zero-sum, we also have to think carefully about WHO our friends are. Perhaps we should be jettisoning some of our friends (eg relatively rich, powerful people) to increase the possibility of making others (particularly downtrodden, marginalised people).

    One question - what happens when people within our 150 have children, or marry outside of our 150 true friends? Do we see the children as subsets of the friendship groups we have or do they become part of the 150 and push out other people?

  4. I see this blog as an ongoing Apologist letter for churches that stagnant and don't grow. Now 150 is our bandwith. How many people has the writer ever managed? I would guess that he sits in his small Christian Univ. in a department of about 10. Organizations of 150 require a leadership structure. Most churces find it necessary to appoint Elders as the memberships hits around 75, otherwise there is to much disfunctionality. Whose Army was the writer in? Has he never heard of a company CO,XO, Platoon Ldr, 1st Sgt, Plt. Sgt, Squad Ldr, Team Ldr? The Army runs organizational structure.

    Organizational and leadership management was developed over the past 200 years, so that organizations could grow, develop, and efficiently strive to meet the goals of the organization. If you can't get past the 150 number in your organization, you have a leadership problem. Get new leaders! If you want a "Hunter - Gatherer Group" join the Mennonites. Otherwise grow up!

    My next problem comes with the writers fear of cliques and that holy pursuit of egalitarianism. Within fully productive organizations, multi mini groups arise based on age, interests, abilities, socio-economics, etc. The job of leaders is to harness the energies and abilities of these different groups in the accomplishment of the organization's goal. Unless the goal of the organization is egalitarianism, squashing these groups for a race to the lowest dommon denominator only guarantees your organization will never get over 50.

    Sandy Fitzgerald
    Centennial, CO

  5. Hi Tim,
    I wouldn't read the 150 too literally. We clearly have the mental capacity to handle huge numbers if needed. The essay was basically using a lot of interesting psychological research to make the same point of the last post: Our psychology naturally carves the world in to family vs. strangers and this tendency can be a moral barrier, if we don't intentionally, in moment to moment encounters, suppress it.

    Hi Sandy,
    Thanks for the comment but I must say it was a colossal exercise in missing the point.

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