Genotype Phenotype
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Involved
- Will Braynen (wbraynen AT email.arizona.edu)
- Simon Angus (s.angus AT unsw.edu.au)
- Mollie Poynton mollie.poynton@nurs.utah.edu
- Paul Dwyer pauldwyer@tamu.edu
- Alejandro Balbin (oabalbinr at unal.edu.co)
Concept
Currently, when we do modeling in economics and other social sciences, we are often creating agents purely as strategies -- we have a population of strategies, without regard to the characteristics of the carrier. This is an old debate in biology between Phenotype (observable, measurable traits) and Genotype (normally strategy information such as motivation or game-play (in economics)). Should we worry about the current confounding of the two? .. Perhaps not, but if firms have a motivation/strategy for their behaviour, and (say) lose a production line due to a power-failure, or storm, then essentially their observable characteristics have changed, but their motivations/strategy remains the same (they may have a strategy for dealing with this event, but the point remains).
Criticism of current modeling dogma
In economic / game-theoretic computational models, agents imitate each other's strategies (i.e. genotypes). But this is a mistake (or a simplifying assumption?) because strategies are not publicly accessible nor directly observable. What is publicly observable is behavior (i.e. phenotypes). In other words, in the real world we often copy each other's behavior, but not the contents of each other's heads (beliefs and desires). Agents in a real economic market can't imitate what's internal to the agent. But copying the behavior of a successful agent might always lead to success. For example, Canon might invest in making cheap color printers not because Canon expects to make money off printers, but because it hopes to make money from selling ink cartridges. Similarly, by analogy, a scientist only has access to observable phonemona (e.g. cloud chamber) when building a model of the physical world (i.e. a physical theory), not its internal structure with its theoretical entities (e.g. an electron).
Modeling Thoughts
So we need to build a richer description of agents that are embodied in some way. Some have done this in the biological evolutionary literature by using external 'tagging' to indicate type characteristics, but these often have nothing to do with genotype, they are normally just modelling tools. (One could argue this for the firm model above -- that the firm loses a part of its 'body' is not coded for by strategy.) In economics, we need to ask what is a phenotype for a firm? What is it above and beyond its strategic decisions? Or for an individual, what determines its fitness/success, independent of its strategic play?
This ties into ideas of levels of selection -- what we are really arguing is that strategies do not play strategies, but individuals who have a strategy play against other individuals with their own strategy. The battle is at the observable/phenotypic scale, not the strategic... or is it?
Are we just talking about path-dependence in an agent's fitness/relative-success? .. for instance, the classical definition of phenotypic variation is given in the wikipedia link above:
genotype + environment + random-variation → phenotype
or for our purposes we would have:
strategy + environment + random-variation → phenotype
recall, these are leading to how the agent now behaves, not how it fairs in the world (which can also be affected by 'environment' and 'random-variation' at the discretion of the modeller...)
Thinking about this some more, finite state automata might be a good example of an agent model for such a difference. Since the behaviour of an agent might be 'All-D' towards one agent, but towards another (because of the complex state arrangement of the FSA) it might play 'CDDDCCCDDD...etc.' and give a rich behavioural basis, and this, from the single genotype (strategy encodded by the FSA). But is this enough?
Another possible model: instead of merely having genotype imitators, we could have three types of agents: (1) traditional genotype imitators, (2) phenotype imitators that copy behavior, (3) some combination of the two. Expected result?
Other Notes and Thoughts
One of the most accepted views of "the firm" is Barney's (1991) Resource Based View of the Firm (RBV) which postulates that firms can only achieve and sustain competitive advantage if they have superior resources (tangible and intangible) and a means of keeping other firms from copying them. This idea has been recently extended by the "dynamic capability perspective" that says the most successful firms are the ones that can most quickly adapt to their changing environment by adapting existing resources and acquiring new ones (this adaptability itself being a resource). Could this be factored into the model above? Or is it already there?