Modelling a Social Agent: Part 2 (Imperfect Rationality)
June 15, 2012 – 10:33 amThe perfectly informed and perfectly rational agent (assumed here) is acceptable for a first approximation of agency; however, it is reasonably easy to modify the formulae above to take account of various forms of imperfection.
Functions and variables, V say, that are estimated by x or are otherwise subjective wrt x shall be denoted E(x)[ V ].
- The point of including x in that notation is that later we will want to be able to account for subjective judgements by x of subjective judgements by y, etc.
- Until that complexity is introduced we shall simply write E[ V ]
The partial satisfaction functions may be imperfectly known or imperfectly applied. Instead of the function S(c, j, x) we need to apply the function E[ S(c, j, x) ] which is a function that returns the Expected Partial Satisfaction of interest j for agent x in context c.
- We note that the expected partial satisfaction function may have little to no relationship to the partial satisfaction function.
We do assume that the Expected Total Satisfaction function (E[ TS ]) is unchanged in form (modulo the partial satisfactions) from TS.
- The weight functions are operationally determined, so they are not imperfectly known: they are essentially subjective. (I expect controversy on that point from champions of false consciousness arguments.)
- It is unlikely that the agent considers all the interests that he may have. Let the salient interests be denoted E[ I(x) ]
- We can restrict the E[ TS ] sum to just the psychologically salient interests.
E[ TS(c, I(x), x) ] = ∑j∈E[I(x)]wj(x)E[ S(C(b, x) , j, x) ]
For each behaviour the agent will need to consider a range of Subjectively Possible Outcomes, rather than the single outcome that is actually determined by the laws of nature: let this be noted as E[ C(b, x) ] = {c1, …, cm}
- Each subjectively possible outcome, c, has an associated Subjective Estimate of Probability, E[ P(c) ], where ∑c∈E[C(b, x)] E[ P(c) ] = 1
- To determine the satisfaction potential of an action b the agent x will consider the likely satisfactions to be had from each subjectively possible outcome of the action and weight it by the subjective estimate of probability of that outcome. Thus, for b ∈ B(x), j ∈ I(x),
E[ S(C(b, x), j, x) ] = ∑c∈E[C(b,x)] E[ P(c) ]E[ S(c, j, x) ]
- We thus require the further modification of the expected total satisfaction function for the action b of x:
E[ TS(C(b, x), I(x), x) ] = ∑j∈E[I(x)]wj(x)E[ S(C(b, x) , j, x) ]
= ∑j∈E[I(x)]wj(x)∑c∈E[C(b, x)] E[ P(c) ]E[ S(c, j, x) ]
It is certain that the agent will not consider all possible behaviours. The set of Subjectively Possible Behaviours that the agent considers live options will be denoted E[ B(x) ]
Granted these forms of limited rationality, the behaviour produced by the agent will maximize the expected total satisfaction of all subjectively possible behaviours, yielding an output behaviour bout, such that:
Tags:E[ TS(C(bout, x), I(x), x) ] = max{E[ TS(C(b, x), I (x), x) ]: b ∈ E[ B(x) ]}
= max{∑j∈E[I(x)]wj(x)∑c∈E[C(b, x)] E[ P(c) ]E[ S(c, j, x) ]: b ∈ E[ B(x) ]}