Collective Behaviour Dr Andrew Jackson Zoology School of Natural Sciences Trinity Centre for Biodiversity Research Trinity College Dublin
Examples from Cells to Beasts
Advantageous Information Transfer
Collective Behaviour
Complex Social Environment
from simple individuals…. How do we get … to complex groups?
The basic rules 1.Personal space - cant occupy the same space as someone else 2.Imitation - tend to copy others and will seemingly follow another without prompting 3.Gregarious – they don’t like being on their own, so will move towards others if isolated
Blind Spot Individual Based Model (IBM) Repulsion Orientation Attraction
Local Interactions
Collective behaviour Emerges as a result of interactions between individual “agents”. Properties of the group are not encoded directly by behaviours at the individual level. Patterns emerge through self-organisation of the system
Matlab example
Sensitivity to individual behaviours Vary only the zone of orientation Blind Spot
Swarming Small zone of orientation
Matlab Swarms
Torus (ring-doughnut) patterns Intermediate zone of orientation
Matlab Torus
College Park Torus
Directed Shoal Large zone of orientation
Matlab Directed Shoals
Variation in behaviour Matlab example (swim speed) Individuals are different
Fast-slow video
Finding your way around your group Fast Larger zone of repulsion High Rate of Turning
Subtle behavioural changes Gives evolution an easy (well easier) way to effect dramatic change at the group level pattern – Key concept in developmental biology Don’t need complex cognitive processing and rules to navigate and negotiate the group complex
But clearly some individuals do have information… Collective Decision Making
Coercion is easy
… but depends on numbers
Few informed individuals Crowd video – few informed individuals
Many informed individuals Crowd video – many informed individuals
Conflict of information Crowd video – conflict of information
Few individuals can sway a group Only a small proportion of informed individuals needed to influence the crowd Larger groups need smaller proportion of informed individuals reach a collective decision
Conclusions Complex collective behaviour derived from local interactions between individuals. Group level properties emerge – the whole is greater than the sum of its parts. Need to take a holistic approach to these systems.
Suggested Reading Dyer, J. R. G., Johansson, A., Helbing, D., Couzin, I. D., & Krause, J. (2009). Leadership, consensus decision making and collective behaviour in humans. Philosophical Transactions of the Royal Society B: Biological Sciences, 364(1518), [pdf]pdf Couzin, I. D. (2007). Collective minds. Nature, 445(7129), [pdf]pdf Couzin, I. D. (2006). Behavioral Ecology: Social Organization in Fission-Fusion Societies. Current Biology, 16(5), r169-r171. [pdf]pdf Couzin et al Collective memory and spatial sorting in animal groups. J Theor Biol. 218, doidoi I suggest you watch this short 5 minute video about collective behaviour by Prof Iain Couzin and basically anything Iain publishes is pretty cool by me And the starlings are always worth viewing -