To cooperatively transport a large load, it is important that carriers conform in their efforts and align their forces. A downside of behavioural conformism is that it may decrease the group's responsiveness to external information. Combining experiment and theory, we show how ants optimize collective transport. On the single-ant scale, optimization stems from decision rules that balance individuality and compliance. Macroscopically, these rules poise the system at the transition between random walk and ballistic motion where the collective response to the steering of a single informed ant is maximized. We relate this peak in response to the divergence of susceptibility at a phase transition. Our theoretical models predict that the ant-load system can be transitioned through the critical point of this mesoscopic system by varying its size; we present experiments supporting these predictions. Our findings show that efficient group-level processes can arise from transient amplification of individual-based knowledge.

Exploration is a central component of human and animal behavior that has been studied in rodents for almost a century. The measures used by neuroscientists to characterize full-blown exploration are limited in exposing the dynamics of the exploratory process, leaving the morphogenesis of its structure and meaning hidden. By unfettering exploration from constraints imposed by hunger, thirst, coercion, and the confines of small cage and short session, using advanced computational tools, we reveal its meaning in the operational world of the mouse. Exploration consists of reiterated roundtrips of increasing amplitude and freedom, involving an increase in the number of independent dimensions along which the mouse moves (macro degrees of freedom). This measurable gradient can serve as a standard reference scale for the developmental dynamics of some aspects of the mouse's emotional-cognitive state and for the study of the interface between behavior and the neurophysiologic and genetic processes mediating it. dimensionality emergence assay (DIEM assay) ͉ dynamics of exploration ͉ mouse open field behavior ͉ neophobia E xploration is the process by which animals and man familiarize themselves with a novel environment. The drive to explore is so fundamental that it overrides most of the other drives: Man enters life-threatening situations in his exploration of ever new territories on the planet and in outer space, and a dam rat placed in an unforeseen environment together with its pups, first explores the new territory extensively and only then attends to the pups. Exploratory behavior has been studied in rodents for almost a century in two main setups-in mazes (1,2) and in the open field test (3). While mazes are most appropriate for testing formulated hypotheses because they impose a priori constraints on the path, the paucity of such constraints in the open field arena highlights intrinsic constraints, offering unexpected hypotheses (4-10). The open field is one of the most common tests in the study of navigation (11), curiosity (12), anxiety (13, 14), lesion-induced (15), drug-induced (16, 17), genetically engineered behavior (18,19), and behavior of animal models of psychiatric diseases (20, 21). The measurements taken in it consist, however, of statistical summaries (22, 23) disregarding the dynamics of occupancy of a novel environment and the animal's moment-to-moment emotional and cognitive states. A dynamic representation of these processes and states is clearly indispensable for correlating the behavior with the neurophysiologic processes that mediate the behavior.To reduce external constraints on the mouse's behavior, we extend the arena 10-fold in space and 100-fold in time (to 2.5-m diameter for 45 h). To increase the likelihood of novelty-seeking and inquisition rather than adjustment to novelty we replace the forced and stressful introduction of the mouse into the arena with free exploration from a home-shelter (8,(24)(25)(26)(27), to reduce the likelihood of foraging we provide free supply of food and wat...

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Widely used behavioral assays need re-evaluation and validation against their intended use. We focus here on measures of chronic anxiety in mouse models and posit that widely used assays such as the open-field test are performed at the wrong time, for inadequate durations and using inappropriate mouse strains. We propose that behavioral assays be screened for usefulness on the basis of their replicability across laboratories.

To obtain a perspective on an animal's own functional world, we study its behavior in situations that allow the animal to regulate the growth rate of its behavior and provide us with the opportunity to quantify its moment-by-moment developmental dynamics. Thus, we are able to show that mouse exploratory behavior consists of sequences of repeated motion: iterative processes that increase in extent and complexity, whose presumed function is a systematic active management of input acquired during the exploration of a novel environment. We use this study to demonstrate our approach to quantifying behavior: targeting aspects of behavior that are shown to be actively managed by the animal, and using measures that are discriminative across strains and treatments and replicable across laboratories.