Monkey business – it’s not what you know, but who you know

Thursday 27 June 2013

Squirrel monkeysWell-connected monkeys learn new cultural habits faster, and sometimes better, than their less-popular peers – just as humans do.

A new study, led by the University of St Andrews, shows that squirrel monkeys who are at the heart of their group’s social network  pick up innovations first, and are more likely to acquire local cultural variations in behaviour, like useful new foraging tricks.

The research was carried out by Dr Nicolas Claidière, Ms Emily Messer and  Professor Andrew Whiten of the University of St Andrews in collaboration with Dr Will Hoppitt of Anglia Ruskin University.

It was conducted on two separate groups of squirrel monkeys at the University of St Andrews’ ‘Living Links to Human Evolution’ Research Centre (‘Living Links’) in Edinburgh Zoo. Results are published today in Current Biology.

The team traced the monkeys’ social networks by recording who spent time with whom when the monkeys were in the vicinity of an “artificial fruit” that could be manipulated to extract attractive food rewards.

These observations were then put through a sophisticated statistical procedure that revealed the monkeys’ social networks, with some individuals particularly well connected and at the heart of the network and others more peripheral (see Figure 2 in the paper).

Each monkey was rated on a measure of their ‘centrality’ in this way. (Technically, the scientists measured ‘eigenvector centrality’, which increases with the strength of an individual’s social connections, the more so when these connections are with other ‘central’ individuals – individuals who themselves have numerous and strong social connections.)

The artificial fruits were designed so they could be opened in two different ways, either by lifting a little hatch on the front, or pivoting it from side to side (so the ‘fruit’ was dubbed a ‘pivotage’, rhyming with ‘pinotage’).

The alpha male in one group was briefly separated and trained how to use the lift technique and his equivalent in the other group was trained to use the pivot technique instead, then they were reunited with their respective groups. The alpha males were chosen because they are known often to be a focus of attention.

The scientists found that monkeys who were well-connected in the network were the most likely to successfully pick up the new technique seeded in their group. They were also more likely to acquire the lift technique in the group seeded with ‘lift’, versus the pivot technique in the group seeded with ‘pivot’, so were truly the hubs of these two different monkey ‘cultures’. (Video is available – see Notes to Editors).

Professor Whiten, Professor of Evolutionary and Developmental Psychology at the University of St Andrews, said: “Our study shows that innovations do not just spread randomly in primate groups, but as in humans, are shaped by the monkeys’ social networks”.

Dr Claidiere said: “Research interest in social learning and social network analysis has surged in recent years, and our results are likely to stimulate further research on the spread of innovations in animal social networks.

“We suspect that our focus on a social network relevant to the diffusion of foraging innovations can explain why we found an effect of the network centrality of individuals on their learning.

“Previous research has focused on other relationships, like who grooms whom, which may not correlate with the monkeys’ observational learning in the same way”.

Professor Whiten notes that similar effects were recently identified in a study by others in the group’s research centre, suggesting that innovations in foraging techniques among humpback whales spread along social networks.

Emily Messer, who is completing her PhD on the monkeys in Living Links noted another aspect of the study. “We also found that maternal relationships explained parts of the social network, so some of the diffusion of the new foraging habits were also probably reflecting an emphasis on learning within families,” she said.

Squirrel monkeys

Note to Editors

The paper: Diffusion dynamics of socially learned foraging techniques in two groups of squirrel monkeys is published in Current Biology.

Professor Andrew Whiten is available on:  01334 462073 / 07817368637

Dr Nicolas Claidière – Tel (Living Links) 0131 314 0394 / 07593 329007

Emily Messer – mobile 07734 859077

Images and a video are available.

Previous research on humpback whales.

Issued by the Press Office, University of St Andrews

Contact Fiona MacLeod on 01334 462108 / 0771 414 0559.

Ref: (squirrelmonkey 27/06/13)

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