[SystemSafety] Bounded rationality or ignorance?

[Olwen Morgan]

The points Peter and Martyn raise about why software engineers make poor 
decisions is IMO well worth exploring.

Behavioural economists use what are known as "bounded rationality 
models" to model the behaviour of economic actors in cases where their 
decision making can be affected by (among other things):

(a)    the tractability of the decision problem,

(b)    the cognitive limitations of their minds, and

(c)    the time available to make the decision.

Here's an example of (b) and (c) (sort-of): A project has decided to use 
MCDC coverage as the test coverage domain to be used in unit testing. 
The aim is to get 100% MCDC coverage of developed code units. Owing to 
slippage, a manager decides that to make up for lost time, the project 
will stop unit testing when 80% MCDC coverage has been achieved.

Here we have (typically), a manager who does not realise the risks 
involved in settling for only 80% coverage. Is this a "cognitive 
limitation" or just ignorance? Also the factor involved was not the time 
available to make the decision but the delay that would accrue if the 
project stuck to the 100% coverage target. OK, lets suppose that these 
quibbles are actually implied to be part of (a), (b), and (c) above. In 
any case,cutting testing short is an very common way in which managers 
seek to recover schedule on delayed projects and the scenario above is 
far from unrealistic.

Now the question: How does a bounded rationality model cope with this 
kind of behaviour? One way to look at it is that the manager makes a 
decision based on how he feels he will be evaluated for his performance 
on the project. Unfortunately that does not actually capture the problem 
that the manager is, more than likely, mis-evaluating technical risks 
because he is technically ignorant - as many lamentably are. Using the 
concepts of bounded rationality, one may easily come up with a narrative 
that describes the problem by citing  the factor of "ignorance" but, as 
is lamentably common in behavioural economic models, that ends up merely 
as an exercise in labelling and does not capture the inner dynamics of 
decision-making hampered by ignorance.

For this reason I'm really not optimistic about the prospects for 
behavioural economics actually helping in correcting the problems of 
poor technical decision-making. In fact, though I won't set any of them 
out here, after much time reading in economics, my opinions on what I've 
seen of economics and economists are, even on a good day, largely 
unprintable.

Olwen


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