I'm learning about NEAT from the following paper: http://nn.cs.utexas.edu/downloads/papers/stanley.ec02.pdf

I'm having trouble understanding how adjusted fitness penalizes large species and prevents them from dominating the population, I'll demonstrate my current understanding through an example and hopefully some one will correct my understanding.

let's say we have two species, A and B, species A did really well last generation and were given more children, this generation they have 4 children and thier fitnesses are [8,10,10,12] while B has 2 and thier fitnesses are [9,9] so now thier adjusted fitnesses will be A[2,2.5,2.5,3] and B[4.5,4.5].

now onto distributing children, the paper states :"Every species is assigned a potentially different number of offspring in proportion to the sum of adjusted fitnesses f'i of its member organisms"

So the sum of adjusted fitnesses is 10 for A and 9 for B thus A gets more children and keeps growing, so how does this process penalizes large species and prevent them from dominating the population?

  • 1
    $\begingroup$ Before the children were born, A dominates B with 4/2 = 2.0. Afterwards, even if the parents stay alive, A dominates less: (4+10)/(2+9)=1.27. $\endgroup$ – Albert Hendriks Dec 19 '17 at 21:38

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