Modelling a Social Agent: Part 2 (Imperfect Rationality)

June 15, 2012 – 10:33 am

The 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:

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) ]}

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