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What Macaque Monkeys Might Tell Us About Our Friendships as We Age

Vector pattern with monkeys and hearts

By Geoffrey W. Lane, PhD, ABPP (Geropsychologist)

I’d like to spend this blog post talking about a rather decent-sized bombshell that has rocked the world of lifespan developmental theory and research. Specifically, it is a rather elegant and well-designed study on the social behavior of Barbary macaques in captivity, one that I believe has, at least a little bit, changed the field of lifespan development theory from now on.

For a bit of background – researchers have noticed a tendency through experimental and anecdotal observation for quite a while now – a contrast between older people vs. younger people. It goes like this – older people have a so-called positivity bias in the way they select their friends and conduct themselves.

What do I mean by this?

This idea of the positivity bias is borne largely from the work of Professor Laura Carstensen of the Stanford Center on Longevity. Dr. Carstensen conducted a series of lab studies where they asked younger and older adults to take part in somewhat arcane tasks, e.g., attending to pictures of happy and sad faces as they’re flashed on a computer screen, and then measuring how long subjects paid attention to the faces. Through this and other related research on social cognition, Dr. Carstensen developed something called the theory of socioemotional selectivity, or SST.

Basically, when we’re young (say, in our teens and twenties), it’s normal to have lots of friends and acquaintances, some emotionally satisfying and close, some perhaps not so much. In addition, younger adulthood tends to be characterized by a yen towards gathering information rather than maximizing positive affect (e.g., ‘happiness’). In other words, younger adults are more geared towards making social contacts and learning about the world around them, even if their activities don’t result in any immediate sense of satisfaction or positivity.

Older adults tend to behave differently. As opposed to having lots of acquaintances and friends, they are much more comfortable with a small group of close friends and family, often a group they’ve cultivated for a number of years. Not only that, they seem less motivated by information-seeking for its own sake, and seem to gear their behavior towards pruning away the people and situations that just don’t add to their level of happiness and satisfaction with their lives.

SST has had a good deal of research to support it over time, and I think for the most part, it’s a very solid theory and tends to comport well with other theories. For example, Paul Baltes’ selective optimization with compensation theory looks at the behaviors of older adults as being focused on being selective in one’s behavior in the service of preserving one’s energy and resources. SST also does a good job of replacing other incorrect and ageist theories of development such as the disengagement theory, which suggested that aging was about gradual withdrawal from the world rather than a more selective deployment of resources.

The thing that’s interesting about SST as a theory is that its proponents (at least up until now), constructed the theory to accommodate the idea of time perspective as being a critical feature. (From the Psychology Wiki):

“…the theory contends that it is not age that is causing the goal shifts but age-associated changes in time perspective. Even younger adults have been shown to pursue present-oriented goals when their time perspective is limited by a fatal illness or life changes such as a college graduation and even older adults favor future-oriented goals when they are asked to imagine an extended future for themselves.”

So it’s not just age, but it’s the fact that human beings have an explicit and cognitive appreciation of their age and their relatively lengthened or shortened time perspectives (as is the case for younger or older adults, respectively). This idea makes sense in the context of SST.

When you’re young, you’re all about gathering information, making as many social connections as possible, because, well, you’re trying to establish yourself and learn your way about the world, I suppose – and you know you have your life ahead of you. Conversely, as an older adult, you’re acutely aware of the fact that you’ve lived more than half of your life (or more). You are settled with the prospect of making sure your remaining days are as happy and pleasant as possible, and you have no more time for friends or situations that cause you more stress or heartache than necessary.

Sounds plausible, right?

Let’s get back to macaque monkeys. In the July issue of Current Biology, Laura Almeling and her colleagues decided to see if SST applied in the case of nonhuman primates, specifically looking at a large colony of 166 monkeys housed in a naturalistic environment in Rocamadour, France. This kind of research is very much weighted towards careful, systematic observation. Ms. Almeling and her colleagues were required to basically sit with these monkeys in their enclosures (which, personally, seems somewhat brave of them) and then present older and younger macaque monkeys with pictures and sounds of pre-identified members of their clans, both close friends, as well as more peripheral ‘acquaintances.’

What they found was just as much of a robust effect in these macaque monkeys supporting the broad outlines of SST as there was in humans. From the Discussion:

“We found a sharp loss of monkeys’ interest in the nonsocial environment in young adulthood…”

These Barbary macaque monkeys basically behaved like humans do when they aged – they remained interested in social relationships, but were far more selective about them. They were less interested in nonsocial stimuli in general, they maintained a smaller, tighter social group. Fellow monkeys (young and old), continued to pay attention to them (as evidenced by grooming behavior). This suggests that the decreased range of social behavior noted in these older monkeys was not explained by the behavior of other monkeys.

Here’s the bombshell, from the Conclusion (emphasis added):

“The finding that nonhuman primates experience marked and differential motivational shifts with age, particularly an increasing focus on social over nonsocial stimuli and shrinking circle of social partners, suggests that some of the motivational changes observed during the human lifespan may be grounded much more deeply in evolution than previously assumed and may not be necessarily tied to an awareness of limited lifetime.”

Indeed. Unless I’m missing something here, it seems that in order to have these findings be consistent with SST theory as it’s commonly understood – as really, a socio-cognitive theory of motivational behavior across the lifespan – we must posit that older Barbary macaque monkeys have an appreciation of their own mortality and relatively limited lifespan compared to their younger social partners (which is something that requires proof!).

In short, it looks like Professor Laura Carstensen’s SST theory may require some retooling. Clearly, the proverbial baby does *not* need to be thrown out with the bathwater here. On the plus-side for SST theory, the ‘positivity bias’ is a real thing. So much so that it’s not only consistently observable in humans, but observable (as of here) in nonhuman primates as well.

However, on the negative side, the implication of this research is that because (we assume) monkeys cannot understand the fact they will die at some point, the ‘positivity bias’ cannot be explained by awareness of mortality. It must be something else, something more hard-wired. What this mechanism is has yet to be explained. That – or perhaps it’s possible monkeys understand more about death and dying than we can appreciate.

Either way, clearly, whether it’s from older adult monkeys or humans – there is more to discover.


Almeling, L., Hammerschmidt, K., Sennhenn-Reulen, H., Freund, A. M., & Fischer, J. (2016). Motivational shifts in aging monkeys and the origins of social selectivity. Current Biology, 26(13), 1744-1749.

Carstensen, L. L. (1992). Social and emotional patterns in adulthood: support for socioemotional selectivity theory. Psychology and aging, 7(3), 331.


Geoffrey W. Lane, PhD, ABPP is a board-certified Geropsychologist (ABGERO), who practices with the VA Palo Alto Healthcare System at the Livermore Division, within the Community Living Center (CLC; e.g., nursing home). He has been the staff Geropsychologist at the CLC since 2007. Dr. Lane has clinical and research interests that are varied and include dementia care and behavior management, social robotics, and technological innovations in caregiving and long-term care. When not at the CLC or doing private consulting, Dr. Lane can be found blogging about geriatrics and gerontology, or is selling stuff on the internet, playing with his kids, or binge-watching drama shows on Netflix.

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