Models in IE Lecture 13 System Dynamics 2nd Lecture Systems Archetypes

Lecture 13: Outline More examples of causal-loop diagrams Glucose and Insulin –What is wrong? –How could such a bad system evolve? Natural systems, man-made systems –What to look for when systems behave poorly Common Patterns: System Archetypes –Success to the successful –Escalation

Analysis of an argument or How to make a mountain out of a molehill

A’s anger B’s harshness A’s harshness B’s anger

Mountains out of Molehills Whose fault is it? –“You started it” Cause, effect, and blame are not clear in complex systems

Eat Candy Blood Glucose Level Hunger Level + - +

Eat Candy Blood Glucose Level Hunger Level Insulin Production Delay - +

Oscillations that increase in amplitude over time are a danger signal

Glucose and Insulin How could nature be so stupid? How could such an unfit system survive?

Nature isn’t stupid -- We are! 1st appearance of insulin regulation –10,000,000-70,000,000 years ago 1st appearance of refined sugar –1500 to 2400 years ago

Eat Complex Carbohydrates Blood Glucose Level Hunger Level Insulin Production Delay - +

Eat Complex Carbohydrates Blood Glucose Level Hunger Level Insulin Production Delay - + Eat Candy + + +

Natural & Man-Made Systems 合 Natural systems have usually evolved so that timings work well › Introduce a new element into a smoothly running system and you are lucky if timings remain good › As change rate of technology  this problem occurs more frequently

“The road to hell is paved with good intentions” “The hurrieder I go, the behinder I get” “ The harder we run, the more we seem to stay in the same place”

“When your best isn’t good enough…” “I keep banging my head against the same wall”

Understanding System Performance

System Archetypes Recurring, classic patterns Identified in Peter Senge’s book, The Fifth Discipline (Chapters 6-16, Appendix 2) Should become part of your permanent vocabulary Escalation Balancing loop with delay Success to the successful Tragedy of the commons Limits to growth Shifting the burden

For Next Class… Read about the different system archetypes Bring your book to class Quiz –open book Quiz forecast w.p..8

Feedback: class performance on homework Good but not excellent overall Don’t complain about 6 hours/week! –2nd half of term much harder Many of the harder problems are difficult conceptually, not technically –try harder –try more than once (many already do). Most work on Little’s Law problem, (6a.m, 6pm) was unsatisfactory. Switch majors