Page 350 - Deep Learning

Belief Revision: The Resubsumption Theory 333

Yet another belief parameter is the cognitive utility of a belief. Philosophical
discourse tends to presuppose that the striving for truth is desirable in its own
right, but people do not generate intuitive theories and belief systems for the
sake of knowing something that is true; the latter is a distinctly academic atti-
tude. Truth might be a moral good, but human cognition did not evolve to
seek, establish or possess truths. Natural selection in a hunter-gatherer sce-
nario optimizes survival, not amount of good. Even in contemporary life,
belief systems and informal theories are not normally held as museum pieces,
cherished for their epistemic beauty. Instead, their purpose is to contribute to
the successful completion of life’s tasks: argumentation, decision making, dis-
course comprehension, explanation, prediction, planning and so on.
Cognitive utility is a descendant of the concept of utility defined in the-
ories of decision making, which in turn evolved from the utility concept in
economics. The latter measures how valuable a good or a service is to some-
body. Cognitive utility measures the usefulness of a knowledge representation
to the person whose representation it is. The concept was developed by J. R.
Anderson in the context of the ACT-R theory. Cognitive utility is a function
5
of both benefits and costs. Both benefit and cost are in turn multidimensional
constructs. For example, cost is a function of, at least, cognitive load and time
6
to task completion, while benefit is a function of, at least, frequency of goal
attainment and satisfaction with the typical outcome. Perhaps there are other
factors that influence cognitive utility as well, but it would be rash to exclude
any one of those four.
A belief or belief system does not have to be (objectively) true or consistent
with evidence to have high cognitive utility. For example, we operate quite well
in everyday life on the basis of something akin to the 14th-century impetus
theory of mechanical motion: If you want a ball to travel farther, whack it
harder. The impetus theory contradicts Newton’s laws of motion and is hence
7
false, but it is nevertheless an effective guide for everyday action. A false or
inaccurate belief might generate consequences that are close enough to the
facts that actions based on that belief tend to be successful. The utility of a
belief system is therefore not directly tied to its truth but measures the extent
to which it enables our cognitive processes to run with low cognitive load, fast
task completion, frequent goal attainment and high satisfaction.
To summarize, we have to distinguish the content of a belief – the relevant
proposition – from the various judgments a person can make about it. The
latter can be described as a vector of parameter values. I distinguish between
four such parameters: A belief can be judged as true or false, with a higher
or lower level of confidence; as desirable or undesirable; and as more or less