Tipping the balances of a small world

PloS one, 2012

Relationships we have with our friends, family, or colleagues influence our personal decisions, as well as decisions we make together with others. As in human beings, despotism and egalitarian societies seem to also exist in animals. While studies have shown that social networks constrain many phenomena from amoebae to primates, we still do not know how consensus emerges from the properties of social networks in many biological systems. We created artificial social networks that represent the continuum from centralized to decentralized organization and used an agent-based model to make predictions about the patterns of consensus and collective movements we observed according to the social network. These theoretical results showed that different social networks and especially contrasted ones - star network vs. equal network - led to totally different patterns. Our model showed that, by moving from a centralized network to a decentralized one, the central individual seemed to lose its...

Arxiv preprint cs/0412047, 2004

North American Association for …, 2004

PLOS ONE, 2016

Individual acts of cooperation give rise to dynamic social networks. Traditionally, models for cooperation in structured populations are based on a separation of individual strategies and of population structure. Individuals adopt a strategy-typically cooperation or defection, which determines their behaviour toward their neighbours as defined by an interaction network. Here, we report a behavioural experiment that amalgamates strategies and structure to empirically investigate the dynamics of social networks. The action of paying a cost c to provide a benefit b is represented as a directed link point from the donor to the recipient. Participants can add and/or remove links to up to two recipients in each round. First, we show that dense networks emerge, where individuals are characterized by fairness: they receive to the same extent they provide. More specifically, we investigate how participants use information about the generosity and payoff of others to update their links. It turns out that aversion to payoff inequity was the most consistent update rule: adding links to individuals that are worse off and removing links to individuals that are better off. We then investigate the effect of direct reciprocation, showing that the possibility of direct reciprocation does not increase cooperation as compared to the treatment where participants are totally unaware of who is providing benefits to them.

Journal of Artificial …, 2005

Small-world and power-law network structures have been prominently proposed as models of large networks. However, the assumptions of these models usually lack sociological grounding. We present a computational model grounded in social exchange theory. Agents search attractive exchange partners in a diverse population. Agent use simple decision heuristics, based on imperfect, local information. Computer simulations show that the topological structure of the emergent social network depends heavily upon two sets of conditions, harshness of the exchange game and learning capacities of the agents. Further analysis show that a combination of these conditions affects whether star-like, small-world or power-law structures emerge.

SSRN Electronic Journal, 2016

This paper examines network formation among a connected population with a preference for conformity and leadership. Agents build stable personal relationships to achieve coordinated actions. The network serves as a repository of collective experiences so that cooperation can emerge from simple, myopic, self-serving adaptation to recent events despite the competing impulses of conformity and leadership and despite limiting individuals to only local information. Computational analysis reveals how behavioral tendencies impact network formation and identifies locally stable disequilibrium structures.

In societal-scale decision-making, a collective is faced with the problem of deriving a decision that is in accord with the collective's intentions and values. Modern political institutions utilize representational structures for decision-making such that any individual in the society can, in potential, participate in the decision-making behavior of the collective-even if only indirectly through a proxy representative. An agent-based simulation demonstrates that in traditional representation structures, as the size of the total population increases linearly relative to the number of decision-making representatives, there is an exponential increase in the likelihood that decision outcomes will not accurately reflect the preferences of the collective. In the direction of a remedy, this paper describes a novel social network-based method for societal-scale decisionmaking which greatly improves the accuracy of representative decision outcomes. This work shows promise for the future development of policy-making systems that are supported by the computer and network infrastructure of our society.

2014

The innovations of science often point to ideas and behaviors that must spread and take root in communities to have impact. Ideas, practices, and behaviors need to go from accepted truths on the part of a few scientists to commonplace beliefs and norms in the minds of the many. Moving from scientific discoveries to public good requires social influence. We introduce a structured influence process (SIP) framework to explain how social networks (i.e., the structure of social influence) and human social motives (i.e., the process of social influence wherein one person’s attitudes and behaviors affect another’s) are used collectively to enact social influence within a community. The SIP framework advances the science of scientific communication by positing social influence events that consider both the “who” and the “how” of social influence. This framework synthesizes core ideas from two bodies of research on social influence. The first is network research on social influence structures, which identifies who are the opinion leaders and who among their network of peers shapes their attitudes and behaviors. The second is research on social influence processes in psychology, which explores how human social motives such as the need for accuracy or the need for affiliation stimulate behavior change. We illustrate the practical implications of the SIP framework by applying it to the case of reducing neonatal mortality in India.

Journal of The Royal Society Interface, 2016

The cognitive ability to form social links that can bind individuals together into large cooperative groups for safety and resource sharing was a key development in human evolutionary and social history. The ‘social brain hypothesis’ argues that the size of these social groups is based on a neurologically constrained capacity for maintaining long-term stable relationships. No model to date has been able to combine a specific socio-cognitive mechanism with the discrete scale invariance observed in ethnographic studies. We show that these properties result in nested layers of self-organizing Erdős–Rényi networks formed by each individual's ability to maintain only a small number of social links. Each set of links plays a specific role in the formation of different social groups. The scale invariance in our model is distinct from previous ‘scale-free networks’ studied using much larger social groups; here, the scale invariance is in the relationship between group sizes, rather than...

Throughout the thesis, I study mathematical models that can help explain the dependency of social phenomena in animals and humans on individual traits. The first chapter investigates consensus building in human groups through communication of individual preferences for a course of action. Individuals share and modify these preferences through speaker listener interactions. Personality traits, reputations, and social networks structures effect these modifications and eventually the group will reach a consensus. If there is variation in personality traits, the time to reach consensus is delayed. Reputation models are introduced and explored, finding that those who can best estimate the average initial preference and who have the best knowledge to what the optimal decision is for the group become the most reputable. If there is one individual, an informal leader, who is stubborn, persuasive, reputable, and socially connected then the time to reach consensus is reduced. The second chapter introduces a model for the emergence of play behavior in animals. An individual-based model is proposed where organisms compete for resources in the environment. Play is introduced as a frivolous behavior that increases energy use and the probability of dying. Simulations show that play behavior becomes fixed in the population and the time spent playing is maintained at a low rate in regardless of its costly nature. When play behavior is directly functional by increasing foraging ability, it evolves quickly and the time individuals spend playing increases, but eventually the population of players collapses and play disappears. Play acts as a spiteful behavior in that playing individuals suffer a direct cost to their fitness, but also results in players consuming more resources incurring a greater cost to other individuals in the population through reduced probability of successfully foraging.