Papers

The social brain hypothesis has suggested that social network size (and structure) is constrained by a combination of cognitive processes and the time required to service social relationships. We test this hypothesis in humans using a unique 18-month mobile phone dataset by examining changes in the structure of social networks across a major change in subjects' social and geographical circumstances.  (...) This provides the first direct evidence that social networks are constrained by a combination of cognitive constraints and the time individuals have available for social interaction, confirming one of the key assumptions of the social brain hypothesis.

The persistence of social signatures in human communication

J. Saramaki, E. A. Leicht, E. Lopez, S. G. B. Roberts, F. Reed-Tsochas, R. I. M. Dunbar

http://arxiv.org/abs/1204.5602

In this review, we discuss modularity and hierarchy in biological systems. We review examples from protein structure, genetics, and biological networks of modular partitioning of the geometry of biological space. We review theories to explain modular organization of biology, with a focus on explaining how biology may spontaneously organize to a structured form. That is, we seek to explain how biology nucleated from among the many possibilities in chemistry.

The Emergence of Modularity in Biological Systems

Dirk M. Lorenz, Alice Jeng, Michael W. Deem

http://arxiv.org/abs/1204.5999

Context is everywhere in the human social and cognitive spheres but it is often implicit and unnoticed. However, when one is involved in trying to understand and model the social and cognitive realms context becomes an important factor. This paper is an analysis of the role and effects of context on social simulation and a call for it to be squarely faced by the social simulation community.

Context in social simulation: why it can’t be wished away
Bruce Edmonds
From the issue entitled "Special Issue: Epistemological Perspectives on Simulation"

COMPUTATIONAL & MATHEMATICAL ORGANIZATION THEORY Volume 18, Number 1 (2012), 5-21

http://dx.doi.org/10.1007/s10588-011-9100-z

Can artificially designed networks reach the levels of robustness against local damage which are comparable with those of the biochemical networks of a living cell? We consider a simple model where the flow applied to an input node propagates through the network and arrives at different times to the output nodes, thus generating a pattern of coordinated responses. By using evolutionary optimization algorithms, functional networks – with required time-programmed responses – were constructed. Then, continuing the evolution, such networks were additionally optimized for robustness against deletion of individual nodes or links. In this manner, large ensembles of functional networks with different kinds of robustness were obtained

Design of robust flow processing networks with time-programmed responses

P. Kaluza and A.S. Mikhailov

Eur. Phys. J. B Volume 85, Number 4, April 2012

http://dx.doi.org/10.1140/epjb/e2012-20433-8

In social dilemmas, cooperation among randomly interacting individuals is often difficult to achieve. The situation changes if interactions take place in a network where the network structure jointly evolves with the behavioral strategies of the interacting individuals. In particular, cooperation can be stabilized if individuals tend to cut interaction links when facing adverse neighborhoods.

Zhang C, Zhang J, Weissing FJ, Perc M, Xie G, et al. (2012) Different Reactions to Adverse Neighborhoods in Games of Cooperation. PLoS ONE 7(4): e35183. http://dx.doi.org/10.1371/journal.pone.0035183

Pedestrian crowds can form the substrate of important socially contagious behaviors, including propagation of visual attention, violence, opinions, and emotional state. However, relating individual to collective behavior is often difficult, and quantitative studies have largely used laboratory experimentation. We present two studies in which we tracked the motion and head direction of 3,325 pedestrians in natural crowds to quantify the extent, influence, and context dependence of socially transmitted visual attention.

Visual attention and the acquisition of information in human crowds
Andrew C. Gallup, Joseph J. Hale, David J. T. Sumpter, Simon Garnier, Alex Kacelnik, John R. Krebs, and Iain D. Couzin

PNAS April 23, 2012

http://dx.doi.org/10.1073/pnas.1116141109

A recent study, using a perceptual task, indicated that two heads were better than one provided that the members could communicate freely, presumably sharing their confidence in their judgments. Capitalizing on recent work on subjective confidence, I replicated this effect in the absence of any dyadic interaction by selecting on each trial the decision of the more confident member of a virtual dyad. However, because subjective confidence monitors the consensuality rather than the accuracy of a decision, when most participants were in error, reliance on the more confident member yielded worse decisions than those of the better individual. Assuming that for each issue group decisions are dominated by the more confident member, these results help specify when groups will be more or less accurate than individuals.

When Are Two Heads Better than One and Why?
Asher Koriat

Science 20 April 2012:
Vol. 336 no. 6079 pp. 360-362
http://dx.doi.org/10.1126/science.1216549

The advent of geographic online social networks such as Foursquare, where users voluntarily signal their current location, opens the door to powerful studies on human movement. In particular the fine granularity of the location data, with GPS accuracy down to 10 meters, and the worldwide scale of Foursquare adoption are unprecedented. In this paper we study urban mobility patterns of people in several metropolitan cities around the globe by analyzing a large set of Foursquare users. Surprisingly, while there are variations in human movement in different cities, our analysis shows that those are predominantly due to different distributions of places across different urban environments. Moreover, a universal law for human mobility is identified, which isolates as a key component the rank-distance, factoring in the number of places between origin and destination, rather than pure physical distance, as considered in some previous works. Building on our findings, we also show how a rank-based movement model accurately captures real human movements in different cities. Our results shed new light on the driving factors of urban human mobility, with potential applications for urban planning, location-based advertisement and even social studies.

A tale of many cities: universal patterns in human urban mobility

Anastasios Noulas, Salvatore Scellato, Renaud Lambiotte, Massimiliano Pontil, Cecilia Mascolo

http://arxiv.org/abs/1108.5355

Previous human foraging experiments have shown that human groups routinely undermatch environmental resources much like other animal species. In this experiment, we test whether humans also selectively rely on others as information sources when the environmental state is uncertain, and we also test whether overt signals of other foragers' success influences group matching behavior and group adaptation to a changing environment. The results show evidence of reliance on social information in specific conditions, but participants were primarily influenced by their individual assessments of food location rather than the success of other foragers.

Group Foraging in Dynamic Environments

Michael E. Roberts, Sam Cheesman, Patrick McMullen

http://arxiv.org/abs/1204.3673

The social media website last.fm provides a detailed snapshot of what its users in hundreds of cities listen to each week. After suitably normalizing this data, we use it to test three hypotheses related to the geographic flow of music. The first is that although many of the most popular artists are listened to around the world, music preferences are closely related to nationality, language, and geographic location. We find support for this hypothesis, with a couple of minor, yet interesting, exceptions. Our second hypothesis is that some cities are consistently early adopters of new music (and early to snub stale music). To test this hypothesis, we adapt a method previously used to detect the leadership networks present in flocks of birds. We find empirical support for the claim that a similar leadership network exists among cities, and this finding is the main contribution of the paper. Finally, we test the hypothesis that large cities tend to be ahead of smaller cities-we find only weak support for this hypothesis.

The Geographic Flow of Music

Conrad Lee, Pádraig Cunningham

http://arxiv.org/abs/1204.2677

Empirical data indicate that sexual preferences are critical for maintaining species boundaries, yet theoretical work has suggested that, on their own, they can have only a minimal role in maintaining biodiversity. This is because long-term coexistence within overlapping ranges is thought to be unlikely in the absence of ecological differentiation9. Here we challenge this widely held view by generalizing a standard model of sexual selection to include two ubiquitous features of populations with sexual selection: spatial variation in local carrying capacity, and mate-search costs in females.

Sexual selection enables long-term coexistence despite ecological equivalence

Leithen K. M’Gonigle, Rupert Mazzucco, Sarah P. Otto & Ulf Dieckmann
Nature 484, 506–509 (26 April 2012) http://dx.doi.org/10.1038/nature10971

This special issue of CMOT presents selected papers from the fourth edition of EPOS, a biennial workshop on Epistemological Perspectives on Simulation. Much like its predecessors it was an interdisciplinary forum for researchers who were interested in discussing epistemological aspects of simulation across disciplinary boundaries. Represented disciplines included social sciences, economics, computer science, en- gineering and the natural sciences.

Epistemological perspectives on simulation: overview and introduction
Matthias Meyer and Klaus G. Troitzsch

COMPUTATIONAL & MATHEMATICAL ORGANIZATION THEORY
Volume 18, Number 1 (2012), 1-4

http://dx.doi.org/10.1007/s10588-012-9111-4

This article provides the first comprehensive conceptual account for the imagistic mental machinery that allows us to travel through time—for the time machine in our mind. It is argued that language reveals this imagistic machine and how we use it. Findings from a range of cognitive fields are theoretically unified and a recent proposal about spatialized mental time travel is elaborated on. The following novel distinctions are offered: external versus internal viewing of time; ‘‘watching” time versus projective ‘‘travel” through time; optional versus obligatory mental time travel; mental time travel into anteriority or posteriority versus mental time travel into the past or future; single mental time travel versus nested dual mental time travel; mental time travel in episodic memory versus mental time travel in semantic memory; and ‘‘seeing” versus ‘‘sensing” mental imagery. Theoretical, empirical, and applied implications are discussed.

The Time Machine in Our Mind
Kurt Stocker

Cognitive Science Volume 36, Issue 3, pages 385–420, April 2012

http://dx.doi.org/10.1111/j.1551-6709.2011.01225.x

We study the self-assembly of a complex network of collaborations among self-interested agents. The agents can maintain different levels of cooperation with different partners. Further, they continuously, selectively, and independently adapt the amount of resources allocated to each of their collaborations in order to maximize the obtained payoff. We show analytically that the system approaches a state in which the agents make identical investments, and links produce identical benefits. Despite this high degree of social coordination some agents manage to secure privileged topological positions in the network enabling them to extract high payoffs. Our analytical investigations provide a rationale for the emergence of unidirectional non-reciprocal collaborations and different responses to the withdrawal of a partner from an interaction that have been reported in the psychological literature.

Patterns of cooperation: fairness and coordination in networks of interacting agents

Anne-Ly Do, Lars Rudolf, Thilo Gross

http://arxiv.org/abs/0902.2954

Biological systems are typically modelled by nonlinear differential equations. In an effort to produce high fidelity representations of the underlying phenomena, these models are usually of high dimension and involve multiple temporal and spatial scales. However, this complexity and associated stiffness makes numerical simulation difficult and mathematical analysis impossible. In order to understand the functionality of these systems, these models are usually approximated by lower dimensional descriptions.

Guaranteed error bounds for structured complexity reduction of biochemical networks

Thomas P. Prescott , Antonis Papachristodoulou

Journal of Theoretical Biology Volume 304, 7 July 2012, Pages 172–182

http://dx.doi.org/10.1016/j.jtbi.2012.04.002

FuturICT foundations are social science, complex systems science, and ICT. The main concerns and challenges in the science of complex systems in the context of FuturICT are laid out in this paper with special emphasis on the Complex Systems route to Social Sciences. This include complex systems having: many heterogeneous interacting parts; multiple scales; complicated transition laws; unexpected or unpredicted emergence; sensitive dependence on initial conditions; path-dependent dynamics; networked hierarchical connectivities; interaction of autonomous agents; self-organisation; non-equilibrium dynamics; combinatorial explosion; adaptivity to changing environments; co-evolving subsystems; ill-defined boundaries; and multilevel dynamics.

Challenges in Complex Systems Science

Maxi San Miguel, Jeffrey H. Johnson, Janos Kertesz, Kimmo Kaski, Albert Díaz-Guilera, Robert S. MacKay, Vittorio Loreto, Peter Erdi, Dirk Helbing

http://arxiv.org/abs/1204.4928

Pattern formations are apparent in natural systems ranging from clouds to animal markings, and from sand dunes to shells of microscopic marine organisms. Despite the astonishing range and variety of such structures, many have comparable features. In this article, Philip Ball reviews some of the common patterns found in nature. He explains how they are typically formed through simple, local interactions between many components of a system – a form of physical computation that gives rise to self-organisation and emergent structures and behaviours.

Pattern Formation in Nature: Physical Constraints and Self-Organising Characteristics
Philip Ball

Architectural Design
Special Issue: Material Computation: Higher Integration in Morphogenetic Design
Volume 82, Issue 2, pages 22–27, March/April 2012

http://dx.doi.org/10.1002/ad.1375

Animals behave adaptively in the environment with multiply competing goals. Understanding of the mechanisms underlying such goal-directed behavior remains a challenge for neuroscience as well for adaptive system research. To address this problem we developed an evolutionary model of adaptive behavior in the multigoal stochastic environment. Proposed neuroevolutionary algorithm is based on neuron's duplication as a basic mechanism of agent's recurrent neural network development. Results of simulation demonstrate that in the course of evolution agents acquire the ability to store the short-term memory and, therefore, use it in behavioral strategies with alternative actions. We found that evolution discovered two mechanisms for short-term memory. The first mechanism is integration of sensory signals and ongoing internal neural activity, resulting in emergence of cell groups specialized on alternative actions. And the second mechanism is slow neurodynamical processes that makes possible to code the previous behavioral choice.

Neuroevolution Results in Emergence of Short-Term Memory for Goal-Directed Behavior

Konstantin Lakhman, Mikhail Burtsev

http://arxiv.org/abs/1204.3221