How cavemen, chocolates and a dinner invite nearly destroyed my marriage.


Dinner invites….

It all began with a perfectly ordinary event – my partner, daughters and I were invited around for a late afternoon dinner with some friends one Sunday last month. Usually when you go to someone’s house you bring something – some flowers, something you have made, or a bottle of something (not so much the latter for us now as we are basically drunk all the time in my household). In this instance we’d been quite disorganised and been unable to sort anything out in advance. No problem – we would just pick something up on the way right? Wrong. Just as we were leaving our baby (with impeccable timing) needed a full nappy / outfit change and a comprehensive hosing down(I’ll let you guess why). As a result we arrived at the supermarket at one minute past four, 60 full seconds after it closed, and were barred entry. Even though we knew the people we were seeing (who are super nice squared) would not automatically expect us to bring something we still felt we had a dilemma – walk across town to another shop which may be open, but be quite late (which with kids and eating can be a deal breaker in terms of a pleasant afternoon!) or go empty handed, which felt wrong (or so half of our partnership thought). OK, so it’s a bit of a exaggeration to say my marriage was nearly destroyed by this discussion. But my partner and I did have quite a falling out! In the end we picked something up, were a bit late, and had a fantastic evening. The tension this seemingly minor issue raised did lead me to reflect on why the drive to bring something when we go to someone’s house to eat is so strong, and what psychology has to say about it.

…cavemen and co-operation.

A classic (but not universally accepted) explanation for this is it is a form of reciprocity. We are social beings and one benefit of being in a group is trading favours. Evolutionary psychologists suggests this may have evolved in hunter gatherer times as a response to sporadic access to large perishable food sources (e.g. hunting a game animal). Once one’s own and immediate family’s needs are met, one is left with a calorie source which is declining in value (it goes off, and is no longer needed) and increases in carry cost (you need to defend it from other people and animals). Individuals (or groups of individuals) who were able to give some of this excess to others with the expectation the favour would be returned would prosper relative to those that could not. They could essentially ‘bank’ excess calories for later. This benefit relies on reciprocity – that the receiver will return the calories given later. As such, evolutionary psychologists argue, the tendency to engage in reciprocity evolved over time[1]. It’s a powerful driver – this desire for reciprocity is so strong we feel a sense of complete ‘dis-ease’ if we feel someone has done something for us and we have not paid it back (something advertisers exploit ruthlessly!).

Of course, we rapidly reach a point where we cannot directly trade favours with individuals we know. This is where indirect reciprocity comes in -doing favours for people we don’t know, on the assumption others would do the same for us[2]. The world would basically be a much nicer place if we all placed a bit more trust in indirect reciprocity, and stopped to help strangers more often. Unfortunately, we know not everyone will behave in the same way towards us. If people don’t live up to their end of the bargain, reciprocity breaks down. Thus,a parallel requirement to reciprocity is an ability to detect cheating. There is some evidence that this skill is somewhat hardwired in us.For instance, we find abstract reasoning tasks which eliminate possibilities much more difficult to solve than the same problems presented in terms of people, places and objects(think Cluedo)[3]. Linking it back to our dinner invite dilemma, the evolution from hunter-gather times of a in-built desire to reciprocate may well have led to our falling out, and our subsequent ‘hunt’ for a box of chocolates.

The world would be a better place if we had more faith in indirect reciprocity Share on X

So what can we learn from this? Firstly, security guards will simply not let you into a supermarket on a Sunday if you are a minute late. Full stop. Second – society would simply be a better place if we had a bit more faith in indirect reciprocity and, finally, if you get a dinner invite, don’t put off arranging your reciprocation strategy to avoid dis-ease! Also, remember your partner is probably right ;).


[1] Trivers, R.(1971) The evolution of reciprocal altruism, Quarterly Review of Biology, 46, 35-57.

[2] Nowak, M.A., and Sigmund, K. (1998). Evolution of indirect reciprocity by image scoring. Nature, 393, 573

[3] Cosmides, L., & Tooby, J. (2005). Neurocognitive adaptations designed for social exchange. In D.M. Buss (Ed) Evolutionary Psychology Handbook, Wiley

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Evolution by ClkerFreeVectorImages via pixabay

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