Bruce Hannon's Complexity Digest # 8

Posted by Connie French on Jun 23, 2010 11:05:00 AM

...excerpted from Complexity Digest 2010.13

Putting organizational complexity in its place, McKinsey Quaterly

Summary: Not all complexity is bad for business "but executives don’t always know what kind their company has. They should understand what creates complexity for most employees, remove what doesn’t add value, and channel the rest to employees who can handle it effectively.

First replicating creature spawned in life simulator, New Scientist

Excerpts: F YOU found a self-replicating organism living inside your computer, your first instinct might be to reach for the antivirus software. If, however, you are Andrew Wade, an avid player in the two-dimensional, mathematical universe known as the Game of Life, such a discovery is nothing short of an epiphany. (...)

A first for the game, the replicator demonstrates how astounding complexity can arise from simple beginnings and processes - an echo of life's origins, perhaps. It might help us understand how life on Earth began, or even inspire strategies to build tiny computers.

Small But Slow World: How Network Topology and Burstiness Slow Down Spreading, arXiv

Abstract: Communication networks show the small-world property of short paths, but the spreading dynamics in them turns out slow. We follow the time evolution of information propagation through communication networks by using the SI model with empirical data on contact sequences. We introduce null models where the sequences are randomly shuffled in different ways, enabling us to distinguish between the contributions of different impeding effects. The slowing down of spreading is found to be caused mostly by weight-topology correlations and the bursty activity patterns of individuals.

Cooperation in Large Networks: An Experimental Approach, SFI Working Papers

Abstract: We present a new design of a simple public goods experiment with a large number of players, where up to 80 people in a computer lab have the possibility to connect with others in the room to induce more cooperators to contribute to the public good and overcome the social dilemma. This experimental design explores the possibility of social networks to be used and institutional devices to create the same behavioral responses we observe with small groups (e.g. commitments, social norms, reciprocity, trust, shame, guilt) that seem to induce cooperative behavior in the private provision of public goods. The results of our experiment suggest that the structure of the network affects the players’ ability to communicate "and through it, their cooperation level," and also their willingness to engage in a more costly type of collective action, namely the endogenous creation of new links to individuals previously out of reach. Finally, the information flows in the network seem to reduce uncertainty in the players: players with more links tend to have more stable play strategies.

theory of leadership in human cooperative groups, J Theor Biol.

Excerpt: This paper provides an evolutionary game theoretical model for the acceptance of leadership in cooperative groups. We propose that the effort of a leader can reduce the likelihood that cooperation fails due to free-riding or coordination errors, and that under some circumstances, individuals would prefer to cooperate in a group under the supervision of a leader who receives a share of the group's productivity than to work in an unsupervised group.

Plasticity, Nature

Excerpt: Plasticity refers to the capacity of organisms or cells to alter their phenotype in response to changes in their environment. This property can be studied at the level of the genome (by analysing epigenetic modifications), the individual cell, and the organism (during development of the embryo or changes in behaviour in adults, for example).
In contrast to previously held views, recent studies show that cells are remarkably plastic. Revealing the molecular and cellular mechanisms that underlie this plasticity is a dynamic area of biology and one that holds great promise for developing new therapies.

  • Source: Plasticity, Magdalena Skipper, Ursula Weiss & Noah Gray, DOI: 10.1038/465703a, Nature 465, 703, 2010/06/10

Simulated epidemics in an empirical spatiotemporal network of 50,185 sexual contacts, arXiv

Abstract: We study implications of the dynamical and spatial contact structure between Brazilian escorts and sex-buyers for the spreading of sexually transmitted infections (STI). Despite a highly skewed degree distribution diseases spreading in this contact structure have rather well-defined epidemic thresholds. Temporal effects create a broad distribution of outbreak sizes even if the transmission probability is taken to the hypothetical value of 100%. Temporal correlations speed up outbreaks, especially in the early phase, compared to randomized contact structures. The time-ordering and the network topology, on the other hand, slow down the epidemics. Studying compartmental models we show that the contact structure can probably not support the spread of HIV, not even if individuals were sexually active during the acute infection. We investigate hypothetical means of containing an outbreak and find that travel restrictions are about as efficient as removal of the vertices of highest degree. In general, the type of commercial sex we study seems not like a major factor in STI epidemics.

Biology's First Law: The Tendency for Diversity and Complexity to Increase in Evolutionary Systems, Chicago University Press


Life on earth is characterized by three striking phenomena that demand explanation: adaptation "the fit between organism and environment; diversity "the great variety of organisms; and complexity "the enormous intricacy of their internal structure. Natural selection explains adaptation. But what explains diversity and complexity? This book argues that there exists in evolution a spontaneous tendency toward increased diversity and complexity, one that acts whether natural selection is present or not. They call this tendency a biological law "the Zero-Force Evolutionary Law. This law invites a reconceptualization of the field of the same sort that Newton’s First Law brought to physics.

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