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The Search for a Single Cause
This pitfall is usually signaled by a sentence like "If only X hadn't happened, then Y would never have occurred!" There are sometimes single-point-of-failure items in a design or in a social system. And it may well be that if X hadn't happened then Y would not have happened either--AT LEAST BY WAY OF X. Finding one cause of an accident does not mean one has found all of them. There are at least two documented coding errors in the Therac-25 case, but no real assurance that these are the only ones. Email made it easy for Machado to verbally attack others, but other technologies would have worked well too. Hughes Microelectronics was cited for particular flaws in its inspection system, but the larger culture of safety was in need of repair.
One way to head off this tendency toward simplification is to maintain a system perspective. The levels of analysis in the ImpactCS framework help in this regard, focussing attention on various levels of scale in the system. The socio-technical analysis for each case also helps keep a perspective on the complexity of the system.
This pitfall is related to the search for blame pitfall explained below. When students begin to search for blame, they are usually (though not always) trying to narrow the case down to a single action that simplifies the case.