Social Welfare on the Sugarscape and Its Paradox Li Wang Ross School of Business University of Michigan Ann Arbor, MI

How to Measure the Social Welfare?  Social Welfare on the Sugarscape:  It measures how well artificial agents can coexist on the sugarscape  Under the same conditions (sugar growth rate, environment conditions, agent vision, agent metabolism,…), different behaviors of individual agents and social norms might significantly affect social welfare  “Carrying Capacity” can be a good indicator of social welfare  It is the number of agents that eventually survive on the sugarscape  Maximal value:

What behaviors might improve Social Welfare?  Collaboration:  Sharing information: before an agent moves to the best location, it shares with its current neighbors what it saw => improving its neighbors’ vision  Social responsibility: the richest neighbor of a starving agent donates some sugar to help it survive.  There is no need for “lenders” to remember who the “borrowers” are.  It is not simply the interaction between individuals, but the interaction between individual and society.  Law enforcement:  It makes a more civilized society  Example: –Taxation: agents pay tax according to their wealth (sugar) and the tax income is used to help starving agents survive.

What behaviors might improve Social Welfare? – Cont.  Introducing centralization:  Example: Agents can be randomly divided into small groups. Agents in the same group can hunt and consume sugar together.  Penalizing sugar collecting:  Idea: There are enough sugar to support a larger society. Some agents are starved to die, because some others are too smart. By penalizing the smart ones, social welfare gets improved.  Simplest and easiest way to improve social welfare  A decentralized approach  Previous methods have higher cost, because they require centralization and/or coordination mechanism  Example:  When an agent has amassed a certain level of wealth, its vision is impaired

Penalizing sugar collection  Code: to M ; Motion rule ; vision range 1-6 ……. ifelse (sugar > 400) ifelse (sugar > 400) [ifelse ( vision > 2) [ifelse ( vision > 2) [set vision vision - 2] [set vision vision - 2] [set vision 1] [set vision 1] ] [ifelse ( sugar > 200) [ifelse ( sugar > 200) [ifelse ( vision > 1) [ifelse ( vision > 1) [set vision vision - 1] [set vision vision - 1] [set vision 1] [set vision 1] ] [if ( sugar < 50) [if ( sugar < 50) [ifelse ( vision < 6) [ifelse ( vision < 6) [set vision vision + 1] [set vision vision + 1] [set vision 6] [set vision 6] ] ] ] set neighborhood make-neighborhood vision set neighborhood make-neighborhood vision …… ……end

Result Original Model Modified Model Original Model Modified Model  Interesting Observation: In the modified model, the average vision decreases, but the number of survived agents significantly increases.  Paradox for social welfare on the Sugarscape: intelligent agents destroy social welfare and it is dumb agents who can save the world.