Dunbar’s number arose when a scientist named Robin Dunbar decided to plot the size of primate troops against the volume of the neocortex and came up with a reasonably straight line. He then extended this to human brain volumes and came up with an estimate of 148 for the human “troop,” which he rounded to 150. He argues that this is about the number of emotionally important relationships humans can have, because of the limits of our brains. Naturally, this was criticized as being both too high and too low an estimate. In his most recent formulation, he argues that 150 represents the upper limits of the number of people any one person can have an emotional investment in at any one time. But he also argues that for most people, the break points are 5, 15, 50 and then 150. Five represents the number of truly intimate relationships, fifteen the next layer of intensity, and 50 the usual size of emotionally significant social networks. There is a body of research suggesting these are reasonable estimates, given the difficulty of both defining and measuring such relationships. So why is this relevant to medical organizations?
Having been medical director for dialysis units for many years, I have developed several working hypotheses about unit size and function. For instance, the number of stations should be divisible by four, as usual staffing ratios are about 4:1. I have also noted that units with about 16 stations tend to function best without particularly knowing why until I got to thinking about Dunbar’s number. First, consider staff interactions. A 16 station unit operating six days per week will usually have less than 15 staff members, counting everybody. With this number of staff, it is possible for the team to develop emotionally significant relationships with each other, particularly if staff turnover is low. Of course, the relationships and the culture that develops may be good or bad, but that is a topic for another day. That same unit will operate most efficiently with four shifts of patients, but not maximally full, or about 60 patients. So, it is possible for the staff to develop some emotional relationship with most of the patients—and almost every patient will have relationships with one or more of the staff. But is this good?
Most articles on professionalism stress the idea that care-givers, be they physicians, nurses, or others, can function best if they avoid dual relationships. That is to say, we should only know and interact with the patient within the context of providing medical care. If we don’t have dual relationships, the argument goes, we can be more detached, and thus more effective. The challenge of professionalism is to remain engaged enough, or not too detached, to be able to satisfy the patient’s need for human support. The problem in dialysis units, though, is that the treatments are repetitive and quite lengthy—each nurse is likely to spend up to 14 hours per week with the same patients over many years, so maintaining detachment is extraordinarily difficult. Furthermore, most of my units are in small towns, so it is inevitable that staff and patients know, or know of, each other through various previous relationships, including kinship. As a result, I spend more time counseling and training about avoiding emotional boundary violations—being too involved.
It is difficult, although important, to determine the patient’s reaction to the impact of numbers, but the mandated patient satisfaction surveys show an interesting trend. Regardless of any clinical or financial metric, patient satisfaction with care is higher in the smaller units, probably because of the comfort patients experience from more intense personal relationships with the treating staff. On the other hand, in my largest unit, we have more than 20 staff members and nearly 100 patients, so the “usual” way of staff-patient interaction does not work. Instead, more formal (more professional?) ways of interacting have been instituted. For instance, primary care nursing, where each patient is assigned a primary nurse, is the norm. While this solves the number problem to a degree, it does not seem to be as emotionally satisfying, as judged by patient satisfaction scores, as the same care provided in smaller units.
What do the staff experience? In the absence of formal studies, it is difficult to know, but I propose looking at voluntary staff departures as a way of judging. We have just finished a fiscal year, so we calculated our turnover rate at 14%, compared to the company average of 23%, but three of the departures were retirements. Deciding between voluntary and involuntary departures is problematic, too. While the administrator has terminated employment on occasion, it is more common for the staff person to become aware things aren’t working out and “voluntarily” obtain employment elsewhere. Of course, the number of departures of any sort in our units is small, so looking at this question would involve looking at larger numbers of employees.
Anecdotal evidence from other people within the company suggests units having problems with patient complaints and poor satisfaction scores have a insufficient professional behavior in the workforce. This might reflect the pool of available talent, local hiring practices, or the way they are acculturated, but I also wonder if it might have something to do with Dunbar’s number. Staff not formally trained, or experienced, in dealing with patients in a professional manner, will almost certainly try to treat them the way they treat other people they know well. This may be good or bad, but Dunbar’s data suggest the limits of this approach.
I also suspect Dunbar’s number has something to do with the disaffection medical professionals are having with their practices. Doctors are used to maintaining an arm’s-length relationship with their patients, but typically become all the more dependent on their staff. To survive, medical organizations are becoming larger and larger. As a result, more impersonal, corporate behaviors become the norm. But are these norms in conflict with the basic assumptions of care-givers about the need and value of personal relationships? And are they in conflict with the patient’s need for a stable personal relationship with his/her caregivers? Dunbar’s observations suggest we should look at finding ways to create functional small units where these relationships can flourish, within the larger corporate context, if we are to find a way to manage this conflict in perspectives.
8 November 2017
 Is There a Limit to How Many Friends We Can Have? (Interview with Robin Dunbar, 13 January 2017. Accessed at http://www.npr.org/templates/transcript/transcript.php?storyId=509358157, 5 November 2017.
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