Often people accuse economists of relying on an imperfect view of human nature – a view that is often disparagingly called “homo-economicus“. However, our view of the world does not rely on the individuals being able to perfectly calculate the satisfaction they get from things or perceive every opportunity.
Ultimately all we require is that individuals respond to incentives (derived from the relative costs and benefits of things) and as a result try to set themselves up such that the benefits of their actions exceed the costs (include opportunity costs). Such a situation can occur when individuals are bounded rational.
A good example of bounded rationality comes from the parable of the centipede and its 100 legs. In the parable there is a centipede walking along. Now it co-ordinates its 100 legs without thinking and without calculating – it does so just because it has become part of its nature. Effectively, it is following a rule of thumb which allows it to make the optimal decision.
When asked about how it moves its legs it gets confused and trips – at this level anyone watch the centipede would take this as a failure of rationality, it obviously can’t deal with the complex calculation required to come up with its optimal solution. However, is this really fair? Even though the centipede couldn’t consciously decide how to move its legs, over time it had evolved a rule of thumb that had allowed it to achieve the optimal solution.
Economists “believe” (this is our value judgment here) that individuals create rules of thumb that allow them to achieve the optimal outcome – without having to consciously calculate.
Understanding how these rules of thumb evolve and change in a highly complex and changeable world is a big deal (in the parable the rule of thumb does not shift favourably to the introduction of information!), and is something behavioural and neurological economists are currently studying. However, it is clear from this individuals can still make optimal decisions, even when they aren’t expert calculators with complete information.