In cognitive society, there is a concept called "channel capacity". Channel capacity is the bottleneck in your brain's neural network which limits the amount of certain types of information you can store. For example, you can store a natural limit of about seven consecutive numbers (which is how American phone numbers ended up being seven digits long). This also extends into social networks. Most studies show that you can develop extremely close, family connections (by which I mean, "If this person died I would be crying on the floor") with a maximum of about 12-15 people.
British scientist Robin Dunbar began to study this phenomenon by studying what is called the neocortix ratio. He found that the neocortix ratio was a very good predictor of the size of "packs" or groupings that wild animals would tend to form. Since animals brains are designed similarly to ours, it stands to reason that we would share this natural tendency as well. What Dunbar found was that for humans, the neocortix ratio was 147.8--meaning that each of us naturally wants to be a part of a community of around 150 people or smaller.
When we pass 150 people in a social group, we lack the capacity in our brains to truly empathize and connect with them. We simply cannot truly emotionally connect to a 'tribe' or clan of more than 150 people. What is interesting about this is how often it pops up in history. Dunbar studied 21 hunter-gatherer societies in the world, from all different cultures, and found an average village size of 148.4. He studied military history and found that individual fighting companies in nearly any culture at nearly any time are divided into groups of less than 200--anything more makes communication too difficult, even in the modern era. Dunbar argues that any organizational group of more than 150 people loses the ability to have face-to-face contact, a sense of community, and personal loyalties to others within the group.
Malcolm Gladwell, in his excellent book Tipping Point, finds this to be a key aspect of any successful organization. For an example, he points to Gore Associates--a wildly successful company whose founder said that the key to their success was having factories which were totally self sufficient (from R&D through sales through production) with a maximum cap of 150 people. He said, "[W]e put a hundred and fifty parking spaces in the lot, and when people start parking on the grass, we know it's time to build a new plant."
Dunbar's Number, as it has come to be called, has been demonstrated time and time again by anthropologists, psychologists, and social scientists. It seems that one can only feel a sense of community and connectedness within a group of about 150 people.
I cannot help but think of the local church in relation to Dunbar's Number. In my life as a Christian, I have attended churches of all different sizes: first I attended a church with several thousand members in college; then my wife's home church (700); then a fast-growing evangelical church which began at 75 members and was over 350 when we left; and now I attend a church with perhaps 125-150 people on Sunday morning, including children.
What I have found is that Dunbar's Number holds just as true in churches as in any organization. I believe that this has some very practical influences on our Christian faith.
What is the purpose of the church? It is to meet together, to study the teachings of the Apostles, and to create a brotherhood of fellowship with our brothers and sisters in Christ (cf, Acts 2). And while it is true that 3,000 Christians came to know Christ through Peter's preaching at Pentecost, history shows us that they appear to have met in groups organized just like the synagogues--that is, about 30-75 people per group. These small churches shared collective doctrine, shared money, and shared missions: but they remained individual, autonomous, local bodies of few people.
The modern American church, however, is focused almost exclusively on expanding and building huge churches: the biggest argument among most evangelical leaders is whether their tens of thousands of church members should gather in a huge sports arena each Sunday morning, or have multiple services, or form multiple campuses. Rarely (if ever) will you hear a modern pastor say that he wants a maximum of 150 people and, if we have more, then we need to plant a new church! (The last church I attended got close: they recognized that around 150-200 was the most that they could handle; however, this was approached at their church not through church planting with independent staff, but instead through multiple services and campuses.)
There are clear pragmatic reasons for the modern pastor to want a larger church. It seems that to bring in new Christians to the church today, you must meet their expectations of a flashy show, dozens of ministries and programs, website/podcast access to the church, and a nice building--all of which happen to cost money. And money comes from donations; and donation size is of course directly proportional to the number of "giving units" (families) within the church.
But just because I understand the reasoning that the modern church wants to be a mega-church with million-dollar revenues does not mean I agree that it is right.
You see, Dunbar's Number teaches us that God designed us to seek out communities in groups of about 150. This has a very practical significance for the church body. It means that pastors can only have face-to-face shepherding of their flock if the church size remains around 150 or less. It means that the church can only form a true sense of community with about 150 people in attendance on Sunday morning. It means that adhering to the primary focuses of the Acts 2 church (community, fellowship, having "all things in common", intense study of the Scriptures with your spiritual family, brotherly love with fellow church-members, being "of one accord" on the churches direction) is only possible if your church body stays around 150 adults or fewer.
Imagine the difference that Christians could make in the world if, instead of following the megachurch model, we truly embraced the Dunbar's Number concept. Imagine if, like Gore Associates, we physically forced ourselves to limit our church size: put 75 spaces in the parking lot (150 seats in the auditorium), and if people start parking on the grass, go plant a new church--not a multi-site campus, but a new church with its own pastoral staff and its own name and its own independence. What would the Christian community look like? For one, we would have a far greater sense of family and community within our churches: all the families would know each other, be able to help each other, be able to hold one another accountable. Also we would be spread much greater throughout our regions--instead of one building where 600 people meet, we would have to spread out into four buildings of 150 people each, thus, becoming more community-focused and truly "local", instead of regional. The pastors would be able to lead and shepherd their flocks one on one, face to face. In short...we would be following the example for churches that Jesus' apostles established, and that God seems to have hard-wired into our brains: church families of about 150 people, very closely knitted together, and able to directly impact their very local communities.
There are some practical considerations, of course. Churches of this size would have to give up having huge sanctuaries. They might not be able to have full-time staff members (or very few, perhaps), in order to pay the bills. They might not be able to offer 30 programs and ten ministries. They might not be able to have cutting-edge websites and slick graphics for each sermon series. They might not be able to host conferences or have their own cemetaries. They might not be able to attract those people who have spiritual ADHD, or those who want the comfort of attending church without the responsibilities of taking up the cross and following Christ.
Whatever they choose, I encourage each church to have specific and clear vision in mind: how big do you want to get, and at what point do you break and plant a new autonomous church? Some would say that the answer is infinite--they never will break to create a new church, and never limit the size of their congregation.
As for me...I don't see me seeking out a church larger than 150 in the near future. My experience matches with the findings of Dunbar: a sense of community cannot exist if a group gets larger than 150 people, and a sense of community is exactly the purpose that the Bible gives for the Church to exist.