‘Dunbar’s Number’ may Change the Math of PR

With data an increasingly important element of marketing communications, PR folks may feel like they’re starting to drown in numbers. So one more shouldn’t hurt.

But this number is likely to have a much bigger impact on the ability of communications pros to do their job better, as opposed to the numbers they constantly track on a daily basis (Google Analytics, et al.) and which sometimes get lost in the ether.

It’s called ‘Dunbar’s Number,’ or roughly 150—the ceiling for the maximum number of individuals with whom we can have a genuine social relationship.

Robin Dunbar, an evolutionary psychologist and professor at the University of Oxford, developed Dunbar’s Number. It’s been floating around for more than 20 years, ever since Dunbar wrote a 1992 article in which he used the correlation observed for non-human primates to predict a social group size for humans.

But now that social media is all the rage, Dunbar is “enjoying a newfound popularity” among Silicon Valley programmers, according to a recent article in Bloomberg Businessweek.

The article, which gets into the nitty-gritty of Dunbar’s Number, should be required reading for PR pros who want to make better sense of their social networks—and maybe even generate more solid returns.

“In the same way that human beings can’t breathe under water or run the 100-meter dash in 2.5 seconds or see microwaves with the naked eye, most cannot maintain many more than 150 meaningful relationships. Cognitively, we’re just not built for it,” reads the article.

As PR pros face growing pressure to enhance their outreach programs and cultivate more relationships via social media, Dunbar’s Number should give communications execs serious pause about the effectiveness of their social media strategy.

Even better, it should once and for all put an end to the “spray and play” practice that remains a crutch among PR pros. While there are all sorts of granular details surrounding Dunbar’s Number, the figure is a highfalutin term for the old adage, “less is more.”

With Dunbar’s Number in mind, PR folks may be throwing good money after bad or, at the very least, incurring a lot of waste in their communication efforts.

As social channels have proliferated, PR execs have been conditioned to thinking that an unknown stream of contacts is just a few clicks away. But Dunbar’s Number should provide a clearer understanding of the inherent limitations in trying to befriend 400 people on Facebook or get in the good graces of 200 journalists and/or media influencers.

Social media is a great PR vehicle. But it’s got only so much gas when stacked up against our brain capacity to build effective relationships. PR pros still need to aim high, of course, but Dunbar’s Number makes a convincing case that they need to take selectivity online a lot more seriously.

Follow Matthew Schwartz: @mpsjourno1


  • http://occamsrazr.com Ike Pigott

    Dunbar’s Number has been floated around in social circles for quite some time now, and it always seems to be mis-applied.

    The limit is NOT in how many friends/acquaintances/relationships a person can have — it is the group size where everyone can still know everyone else’s business.

    Put simply, “What is the largest size high school graduating class where everyone knows everyone else’s dating history?”

    What social media has done is force us to have better clarity about exactly What a “connection” is. There are looser ties that we have to people with whom we’ve never shared a meal. We may have a single common interest, and build a working relationship out of that. Those sorts of things were not possible 100 years ago, and some might argue even 20 years ago on a large scale.

    Dunbar is definitely on to something, but the flat quoting of “150” in the way you cite is completely off-base.

  • http://DunbarNumber Brian M

    In a video Dunbar explains the 150 as the number of “relationships of trust or obligation.” There are also other important concentric circles that he mentions like 3 to 5 and 12 to 15.