Agent-Based Modeling: More Examples

PSC 120

Jeff Schank

Ovarian-Cycle Synchrony• Does ovarian-cycle synchrony exist in

mammals?

• The problem of cycle variability

• Ovarian cycles and female mate choice

– The cost of synchrony

Synchrony?• Studies have reported synchrony in

– Women– Norway rats– Golden hamsters– Golden lion tamarins– Chimpanzees

• All are fundamentally flawed and more recent studies have found no effects

Original Results (1971)

Does Menstrual Synchrony Exist?

Does Menstrual Synchrony Exist? Continued…

The Cost of Synchrony• There are two types of fitness costs for

synchronized females– Male quality– Mating opportunities

• To explore these costs, I built an ABM, based on J. B. Calhoun’s study: The Ecology and Sociology of The Norway Rat

Calhoun’s Rats ABM• Aims and Design

– Ecologically realistic– Based on data– 5 to 10 reproductive females at a given

time– 61 adult males (7 high, 12 medium, 42 low)– Movement is determined by “collapsing”

preferences into a local probability space surrounding a model rat

Two views of the Pen

The Trails Map

ABM Model

Syn

chro

ny

Synchrony by Chance

Syn

chro

ny D

istr

ibut

ions

Male Quality & Synchrony

Matings and Synchrony

Male Quality & Cycle Length

Matings & Cycle Length

Conclusions

• Ovarian cycles may have evolved to facilitate female mate choice

• Synchrony has fitness costs

• Cycle variability may have fitness benefits in promiscuous mating systems

The Development of Locomotion

• How do animals do what they do?• How do we answer this question?

• Start simple and work to the complex

• If we want to understand how something works in space and time, it is often a good idea to build it or something like it.

• We cannot just build animals at different stages of development, but we can build models of them, which may help us understand them better (i.e., simulation, robotic)

Rat Pups

• Born with very limited sensorimotor capabilities

– Blind and deaf till days 13 to 15

– Legs cannot lift the body off the ground till after

day 10

• However, they can aggregate in huddles and thermoregulate

Locomotor Development

Behavior in a Temperature Controlled Arena: A Simple Paradigm

Metrics

• Basic metric: tip of nosebase of tail location

• Derived metrics– Activity– Object Contact– Speed – Aggregation– Conditional Probabilities

7 and 10 Day Old Individual Locomotion: Examples

Day 7

Day 10

7 and 10 Day Old Individual & Group Locomotion

Individual

Group

An Agent-Based Model

Row

Column

P P W

E E

E E E

Whole-Body Locomotion Kinematics

Whole-Body Locomotion Kinematics

Genetic Algorithms

• Arrange the parameters of the into a “chromosome”

• Create a population of models

• Perform mutation and crossover on pairs of models

• Run a number of simulations and choose the parameters that best fit the data

Locomotion Kinematic Results

Day 7 Day 10

Individual

Group

7 and 10 Day Subgroup Formation

Day 7 Day 10

7 and 10 Day Old Individual Locomotion: Examples

Day 7

Day 10

Model Examples

Day 7

Day 10