http://friam.383.s1.nabble.com/towards-a-description-of-a-goal-function-relation-tp7597842p7597863.html
Not to change anything there, but to add some nuance:
It MIGHT be the case that the set of all possible goals and the set of all possible functions is isomorphic. Nick's assertion (100% for evolved systems, tentatively for the vast majority of control systems) is that for any given system we will find that the goal and the function differ. The goal of one system might well be the function of a different system.
What are some of the issues we identified in our discussion?
This distinction is fairly intuitive for the evolutionary biologists in the group, because the "evolutionary function" is more or less a given.
The distinction is less intuitive for many others on the list, because (I hypothesized at the end) the function of our standard-discussion control systems is determined by a third party. For example, that the thermostat functions to "regulate temperature throughout the house" from the perspective of the homeowner.
Ultimately we identify both function and goal experimentally, and the two labels develop because two things differentiated experimentally (i.e., for the same reason different chemicals were differentiated by the early experimental chemists).
Example:
Certain gulls that nest on the ground clear broken eggs away from their nests.
Does this serve an anti-parasite function or an anti-predation function? Well, ethologists did a boatload of experiments, and comparison of the behavior of other species, and it showed that the behavior serves the evolutionary function of reducing predation. Closely related species that nest on cliffs, where there are not predators, do not exhibit the behavior. Experimentally thwarting the egg clearing behavior increases predation rates on intact eggs still in the nest. No relation was found with parasite load or loss of eggs or young due to sickness. (Jon rightly pointed out that traits can serve many functions, and that "the function" just a shorthand for something like "we are pretty sure this is the most important one." We could easily pick different examples to show adaptation that optimizes the intersection of various functions.) Birds that, in the past, removed broken egg shells from around their nest, reproduced more successfully than birds that did not, due to egg removal reducing egg-predation incidences, and now all female-birds-in-that-species-with-eggs-in-their-nest exhibit that behavior.
What is the goal of the birds? Well, you might think the goal of the birds was to thwart predation. It wasn't that long ago that evolutionary theorists thought it would all be that simple... but there are more experiments. To study the function, we studied what happens to the gull and its eggs and its young. To study goal we study what the gull does. Turns out, the gull doesn't change its behavior based on risk of predation, including whether it sees predators on the regular, whether neighboring nests or its own nest has been hit, or other similar factors (it changes other behaviors, but not this one). When we start seeing what it does or doesn't clear away, we find that it clears all sorts of things away, and lots of those don't affect predation rates.
What we end up with, when issues are experimentally investigated in depth is most typically as follows: Members of Species A reliably generate Goal X under certain circumstances. In the current environment B, which we have reason to believe is similar to the ancestral environment in key ways, striving for Goal X produces Outcome Y, where Y promotes survival of the individual and/or the individual's offspring. Thus Y can be presumed to be the evolutionary function.
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Eric P. Charles, Ph.D.
Department of Justice - Personnel Psychologist
American University - Adjunct Instructor
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