1. Overview
2. Rules of Behavior
3. Rules of Evolution
4. Changing the Population Characteristics
5. Discussion

Overview

The description below covers the Guardlets applet.

Rules of Behavior

Guardlets behavior is governed by two rules:

1. A rule specifying how to relate to one's own kind.
2. A rule specifying how to relate to Attackers.

Both Guardlets and Attackers are attracted to the resource-critical center screen section. Guardlets attempt to limit excessive access to this area.

1. How to relate to one's own kind

• Identify Guardlets that are near to you and try to stay close to them, but not too close

2. How to relate to Attackers

• Interpose yourself between Attackers and center section if an Attacker is too close for too long

These are the Rewards and Penalties that influence fitness:

• Energy: Guardlets gain energy when moving an Attacker away from the critical center section in proportion to the distance from the center section. An analogy is crowd control where the degree of control required is proportional to the proximity to a critical area.
• Safety: Guardlets gain safety by touching each other, keeping coherent ranks to provide defense.
• Cooperation: Guardlets gain cooperation by moving toward each other.

How to use the applet

• Modifying the static population
• Modifying the evolutionary factors

Modifying the static population

You can do the following:

• Go to 'Edit Properties' and modify the environment, Click 'Update' to apply the new environment"
• Follow individual Guardlets easily by displaying their ID numbers.
  The' Show Numbers/Show Shapes' button toggles between these display modes.
• Turn off (or on again) the sound effects.
• Display information on all Guardlets by clicking the 'Show Info' button.
• Display a Help screen by the 'Show Help' button.
• Select a predefined population from the 'Predefined' screen.
• Reset everything to default by clicking the Restart button.

Modifying the evolutionary factors

You can do the following:

• Modify the fitness function. Go to 'Edit Properties' and assign Energy and Safety and Cooperation Weight Factors
  • If Energy weight is higher, Guardlets will evolve to be braver and possess higher speed and acceleration.
  • If Safety or Cooperation weight is higher, Guardlets will evolve to be more cautious and they will keep together
• Modify the Max Energy Dose or Max Safety Dose properties. This is another way to control evolution direction.
• Create a single new generation by clicking the Breed button. Each selection of 'Breed' will produce a new generation out of the current one.
• You can start the evolution process with various types of populations:
  • Start with a diverse, random population.
    Click 'Start Evolution'.
  • Start with a homogeneous population.
    Use the default population, or one you defined by changing environmental parameters using 'Update' in the 'Edit Properties' screen.
  • Select a predefined evolutionary process from the Predefined screen.
• Limit the possible variation by clicking Limit Ranges button.
  This will ensure a more homogenous, less wild population.
• Examine the history of the evolution by looking in the History page in the Info screen.
• Stop the evolutionary process by clicking the Stop Evolution button.
  (This toggle button displays the label 'Stop Evolution' when evolution is on).

The simple behavioral rules produce interesting emergent behavior. When Guardlets are not disturbed by Attackers they stick more or less together and meander in their home area. However, when an Attacker is introduced it will begin to excite them. The emergent flocking behavior they exhibit seems by its inherent mechanics to disrupt the process of excessive Attacker resource consumption in this model.

• The lowest layer is the genotype:
  This is the actual chromosomal string on which the genes are encoded. The Guardlets genetic algorithm is based on a string of hexadecimal characters, where each group of 4 characters on the chromosome represents a specific trait. At this level, we have only character strings that mean nothing until they are interpreted.
• Here is an example of an encoded chromosome and each trait:
  
• The middle layer is the phenotype:
  Here the information encoded in the genes is translated into behavior, which can be seen in the real world; The Model. For example, a specific character group in a specific location on the chromosome may define a specific Guardlet acceleration. The Guardlet movement we see on the screen is influenced by this value.
• The third layer is the evolutionary fitness:
  The fitness depends on the phenotypic properties, but not always in a direct and simple way. There are no genes for fitness. A Guardlets's fitness is maximized when both energy, safety, and cooperation are maximized.

So we have this chain:
Evolutionary selection is done by fitness, fitness depends on the phenotypic traits, and these are defined by the genetic string. The evolutionary operators themselves (reproduction, crossover and mutation), act on the chromosome string.

And the result can be unpredictable:
By modifying specific traits, we influence the emergent behavior in ways that are not always easy to predict. When the evolution mechanism throws its blind operators, there is almost nothing we can tell in advance. Therefore it is quite interesting to watch the behavior and evolution of Guardlets, even in this very simple system.