Kasper van der Vaart studied physics and astronomy at the University of Amsterdam, where his bachelor thesis, supervised by Tom Gregorkiewicz and Wieteke de Boer, was on the topic of photoluminescence of silicon nano-crystals. Afterwards he went to the University of Utrecht to obtain a M.Sc. in Nano-materials, focussing mostly on nanophotonics and soft matter. Following a project back in Amsterdam on the rheology of colloidal glasses (supervised by Peter Schall) he sought to apply his new found knowledge on rheology to a more everyday material. Thus he ventured in to the field of food technology and performed his master project on chocolate flow behaviour at the laboratory of Food Technology and Engineering at Ghent University, under supervision of Koen Dewettinck. Wanting to visualize the actual particle motion in a soft material, Kasper went to the EPFL in Switzerland. There he investigated particle-size segregation in granular avalanches through both experiments and simulations, in the lab of Christophe Ancey. During this work Kasper collaborated closely with Nico Gray and Anthony Thornton. His current work at Stanford focusses on the collective behavior and emergent properties of midge swarms, in order to determine what constitutes collective behavior, how it can be quantified and how we can compare different collectively behaving organisms.
Doctor of Philosophy, Ecole Polytechnique Federale Lausanne (2016)
Nicholas Ouellette, Postdoctoral Faculty Sponsor
Costs and benefits of social relationships in the collective motion of bird flocks.
Nature ecology & evolution
Current understanding of collective behaviour in nature is based largely on models that assume that identical agents obey the same interaction rules, but in reality interactions may be influenced by social relationships among group members. Here, we show that social relationships transform local interactions and collective dynamics. We tracked individuals' three-dimensional trajectories within flocks of jackdaws, a species that forms lifelong pair-bonds. Reflecting this social system, we find that flocks contain internal sub-structure, with discrete pairs of individuals tied together by spring-like effective forces. Within flocks, paired birds interacted with fewer neighbours than unpaired birds and flapped their wings more slowly, which may result in energy savings. However, flocks with more paired birds had shorter correlation lengths, which is likely to inhibit efficient information transfer through the flock. Similar changes to group properties emerge naturally from a generic self-propelled particle model. These results reveal a critical tension between individual- and group-level benefits during collective behaviour in species with differentiated social relationships, and have major evolutionary and cognitive implications.
View details for PubMedID 31061474
- Three-dimensional time-resolved trajectories from laboratory insect swarms SCIENTIFIC DATA 2019; 6
Response of insect swarms to dynamic illumination perturbations.
Journal of the Royal Society, Interface
2019; 16 (150): 20180739
Many animal species across taxa spontaneously form aggregations that exhibit collective behaviour. In the wild, these collective systems are unavoidably influenced by ubiquitous environmental perturbations such as wind gusts, acoustic and visual stimuli, or the presence of predators or other animals. The way these environmental perturbations influence the animals' collective behaviour, however, is poorly understood, in part because conducting controlled quantitative perturbation experiments in natural settings is challenging. To circumvent the need for controlling environmental conditions in the field, we study swarming midges in a laboratory experiment where we have full control over external perturbations. Here, we consider the effect of controlled variable light exposure on the swarming behaviour. We find that not only do individuals in the swarm respond to light changes by speeding up during brighter conditions but also the swarm as a whole responds to these perturbations by compressing and simultaneously increasing the attraction of individual midges to its centre of mass. The swarm-level response can be described by making an analogy to classical thermodynamics, with the state of the swarm moving along an isotherm in a thermodynamic phase plane.
View details for PubMedID 30958145
View details for PubMedCentralID PMC6364661
- Response of insect swarms to dynamic illumination perturbations JOURNAL OF THE ROYAL SOCIETY INTERFACE 2019; 16 (150)
MERCURYDPM: FAST, FLEXIBLE PARTICLE SIMULATIONS IN COMPLEX GEOMETRIES PART II: APPLICATIONS
INT CENTER NUMERICAL METHODS ENGINEERING. 2017: 123–34
View details for Web of Science ID 000426873800010