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
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
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
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), 781-789. [pdf]pdf Couzin, I. D. (2007). Collective minds. Nature, 445(7129), 715-715. [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. 2002. Collective memory and spatial sorting in animal groups. J Theor Biol. 218, 1-11. doidoi I suggest you watch this short 5 minute video about collective behaviour by Prof Iain Couzin http://youtu.be/_2WqH_HUxz8, and basically anything Iain publishes is pretty cool by me http://icouzin.princeton.edu/http://youtu.be/_2WqH_HUxz8http://icouzin.princeton.edu/ And the starlings are always worth viewing - http://vimeo.com/31158841http://vimeo.com/31158841