| 1. |
- Nicolis, Stamatios C., et al.
(författare)
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Foraging at the Edge of Chaos : Internal Clock versus External Forcing
- 2013
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 110:26, s. 268104-
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Tidskriftsartikel (refereegranskat)abstract
- Activity rhythms in animal groups arise both from external changes in the environment, as well as from internal group dynamics. These cycles are reminiscent of physical and chemical systems with quasiperiodic and even chaotic behavior resulting from "autocatalytic'' mechanisms. We use nonlinear differential equations to model how the coupling between the self-excitatory interactions of individuals and external forcing can produce four different types of activity rhythms: quasiperiodic, chaotic, phase locked, and displaying over or under shooting. At the transition between quasiperiodic and chaotic regimes, activity cycles are asymmetrical, with rapid activity increases and slower decreases and a phase shift between external forcing and activity. We find similar activity patterns in ant colonies in response to varying temperature during the day. Thus foraging ants operate in a region of quasiperiodicity close to a cascade of transitions leading to chaos. The model suggests that a wide range of temporal structures and irregularities seen in the activity of animal and human groups might be accounted for by the coupling between collectively generated internal clocks and external forcings.
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| 2. |
- Arganda, S., et al.
(författare)
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Collective choice in ants : The role of protein and carbohydrates ratios
- 2014
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Ingår i: Journal of insect physiology. - : Elsevier BV. - 0022-1910 .- 1879-1611. ; 69, s. 19-26
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Tidskriftsartikel (refereegranskat)abstract
- In a foraging context, social insects make collective decisions from individuals responding to local information. When faced with foods varying in quality, ants are known to be able to select the best food source using pheromone trails. Until now, studies investigating collective decisions have focused on single nutrients, mostly carbohydrates. In the environment, the foods available are a complex mixture and are composed of various nutrients, available in different forms. In this paper, we explore the effect of protein to carbohydrate ratio on ants' ability to detect and choose between foods with different protein characteristics (free amino acids or whole proteins). In a two-choice set up, Argentine ants Linepithema humile were presented with two artificial foods containing either whole protein or amino acids in two different dietary conditions: high protein food or high carbohydrate food. At the collective level, when ants were faced with high carbohydrate foods, they did not show a preference between free amino acids or whole proteins, while a preference for free amino acids emerged when choosing between high protein foods. At the individual level, the probability of feeding was higher for high carbohydrates food and for foods containing free amino acids. Two mathematical models were developed to evaluate the importance of feeding probability in collective food selection. A first model in which a forager deposits pheromone only after feeding, and a second model in which a forager always deposits pheromone, but with greater intensity after feeding. Both models were able to predict free amino acid selection, however the second one was better able to reproduce the experimental results suggesting that modulating trail strength according to feeding probability is likely the mechanism explaining amino acid preference at a collective level in Argentine ants.
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| 3. |
- Nicolis, Catherine, et al.
(författare)
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Return time statistics of extreme events in deterministic dynamical systems
- 2007
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Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 80:4, s. 40003-40008
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that deterministic dynamics leaves a clearcut signature on the statistical properties of the return time of extreme events, giving rise to properties that are not accounted for by the classical statistical approach. Analytical expressions are derived, compared to those of classical statistical theory and applied to generic examples of dynamical systems giving rise to quasi-periodic, strongly chaotic and intermittent chaotic behaviors. Copyright (c) EPLA, 2007.
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| 4. |
- Nicolis, Gregoire, et al.
(författare)
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Probabilistic Network Approach to Decision-Making
- 2015
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Ingår i: Open systems & information dynamics. - 1230-1612 .- 1573-1324. ; 22:2
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Tidskriftsartikel (refereegranskat)abstract
- A probabilistic approach to decision-making is developed in which the states of the underlying stochastic process, assumed to be of the Markov type, represent the competing options. The principal parameters determining the dominance of a particular option versus the others are identified and the transduction of information associated to the transitions between states is quantified using a set of entropy-like quantities.
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| 5. |
- Nicolis, H., et al.
(författare)
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The Selfish to Egalitarian Transition in Young Children : Developmental Processes versus Cooperative Interactions
- 2010
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Ingår i: Nonlinear Dynamics, Psychology, and Life Sciences. - 1090-0578 .- 1573-6652. ; 14:3, s. 257-264
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Tidskriftsartikel (refereegranskat)abstract
- There is evidence that a tendency to share resources equitably among members of a social group emerges in middle childhood. It is regarded by many investigators as a central and unique feature of human social life. In this work the relative roles of developmental processes and collective effects generated by interindiviclual interactions on the selfish to egalitarian transition observed in middle childhood are analyzed. Using mathematical modeling, conditions are identified under which the transition becomes sharp and gives rise to hysteretic behavior.
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| 6. |
- Nicolis, Stamatios C., et al.
(författare)
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Dynamics of Collective Decisions in a Time-Dependent Environment
- 2014
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Ingår i: International Journal of Bifurcation and Chaos in Applied Sciences and Engineering. - 0218-1274. ; 24:8, s. 1440010-
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Tidskriftsartikel (refereegranskat)abstract
- The field of dynamical systems had been revolutionized by the seminal work of Leonid Shil'nikov. As a tribute to his genius we analyze in this paper the response of dynamical systems to systematic variations of a control parameter in time, using a normal form approach. Explicit expressions of the normal forms and of their parameter dependences are derived for a class of systems possessing multiple steady-states associated to collective choices between several options in group-living organisms, giving rise to bifurcations of the pitchfork and of the limit point type. Depending on the conditions, delays in the transitions between states, stabilization of metastable states, or on the contrary enhancement of the choice of the most rewarding option induced by the time dependence of the parameter are identified.
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| 7. |
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| 8. |
- Dussutour, Audrey, et al.
(författare)
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Collective decisions in ants when foraging under crowded conditions
- 2006
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Ingår i: Behavioral Ecology and Sociobiology. - : Springer Science and Business Media LLC. - 0340-5443 .- 1432-0762. ; 61, s. 17-30
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we examine the effect of crowding on the selection of a path in the mass-recruiting ant Lasius niger. In our experiment, ants had to go from their nest to a food source by crossing a diamond-shaped bridge, giving the choice between two paths. Two types of bridges were used: the first had two branches of equal length but different width while the second had two branches of different length and width. Experiments at high traffic volume always ended up with the selection of the wider branch, even if it was longer. This result shows that overcrowding on the narrow branch plays an essential role in the mechanism underlying the choice of route in ants. A mathematical model was developed to evaluate the importance of two mechanisms that could account for this result. The first is based on the difference in travel duration between the two paths. The second is based on the repulsive interactions between workers making head-on encounters. The model shows that travel duration per se is not sufficient to explain path choice. Rather, it is the interplay between trail following behaviour and repulsive interactions that allows ants to choose the path that minimizes their travel time. When choosing a path ants thus prefer to trade time against energy. Our results demonstrate that any environmental constraint that alters the dynamics of trail recruitment can lead to the emergence of adaptive foraging decisions without any explicit coding of information by the foragers at the individual level.
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| 9. |
- Dussutour, Audrey, et al.
(författare)
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Flexibility in collective decision-making by ant colonies : Tracking food across space and time
- 2013
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Ingår i: Chaos, Solitons & Fractals. - : Elsevier BV. - 0960-0779 .- 1873-2887. ; 50:SI, s. 32-38
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Tidskriftsartikel (refereegranskat)abstract
- Deciding which of many available resources to exploit is a problem faced by a range of decentralized biological systems. For example, ants are able to choose between food sources that vary in quality using a chemical trail. This communication system characterized by a strong positive feedback allows a rapid transfer of information and the selection of the best food source. This is true in static environment, where a single, unchanging solution exists. In dynamic environments however such recruitment often 'lock' groups into suboptimal decisions, preventing a response to changes in available resources. Here, we investigate decision-making in a dynamic environment for the greenhead ants (Rhytidoponera metallica) which use a non-chemical recruitment. To experimentally test our study species' ability to adapt to changes in their foraging environment, we offered three feeders that changed in quality. At any given time, only one feeder provided high quality food, while the others provided low quality food. Every two hours, the quality of the feeders changed such that the previously high quality feeder became a low quality feeder, and vice versa. We showed that ants were able to track changes in food quality across space and time. By coupling behavioral observations to computer simulations, we demonstrate that selection of food sources relies uniquely on a retention effect of feeding individuals on newcomers without comparison between available opportunities. The elegance of these parsimonious foraging systems is that the collective decision arises from the perception of conspecifics without the need for a leader having a synoptic overall view of the situation and knowing all the available options.
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| 10. |
- Dussutour, Audrey, et al.
(författare)
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How do ants and social caterpillars collectively make decisions?
- 2007
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Ingår i: Cognitive Decision-Making: Empirical and Foundational issues. - Cambridge : Cambridge Scholars Publishing. ; , s. 48-65
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Bokkapitel (refereegranskat)abstract
- Cognitive Decision-Making is an interdisciplinary collection of essays in psychology, philosophy, neuroscience and biology about decision-making. While it has been a topic for economists, logicians and psychologists for many years, decision-making is gaining more attention now from a diverse array of approaches. In 2005, a conference was held at the UniversitÈ du QuÈbec at Montreal (UQAM) and allowed researchers from various fields to interact and discuss such issues. Cognitio 2005 was an occasion for philosophers, cognitive scientists and biologists to present the latest development in their discipline, and this book aims at providing a general overview of current research in the field of cognitive decision-making. This book is intended for scholars interested in the nature, modeling, evolution and substrate of decision-making.
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