Human actions must always meet multiple, changing, and often conflicting criteria to performance. Humans are usually able to cope with this imposed complexity because they can adjust what they do and how they do it to match the current conditions. This ability has been described in several ways by terms such as adaptation, optimisation (and sub-optimisation), satisficing, suffisance, minimising cognitive effort, minimising workload, balancing arousal, etc. It is probably impossible to account for this behaviour using a single criterion or concept, and the issue here is not to attempt a comprehensive description of how this adjustment, adaptation or optimisation takes place, but rather to consider the consequences it has.
As a starting point, we take for granted that people constantly try to optimise their performance. This is tantamount to striking a balance between resources and demands, where both may vary over time, and involves making a trade-off between efficiency and thoroughness. On the one hand people genuinely try to meet their (internalised) goals, i.e., they try to do what they are supposed to do – or at least what they intend to do – and to be as thorough in accomplishing that as they believe is necessary. On the other hand they try to do this as efficiently as possible, which means that they try to do it without spending unnecessary effort or wasting time.
In making this trade-off people are greatly helped by the regularity or stability of their work environment and, indeed, the regularity of the world at large. If the work environment was continually changing it would be unpredictable. Such a lack of predictability would in effect make it impossible to take any shortcuts or indeed to learn how things could be done in a more efficient manner. It is precisely because the work environment has some measure of regularity or stability that it becomes predictable, and therefore allows performance to be optimised by skipping the bits that are normally unnecessary.
The benefits of making shortcuts are obvious: they save time and effort. If a person “always” can assume that condition A is true in situation B, then there is no real need to check the condition. Instead of checking every possible condition or prerequisite of an action, efforts can be reserved to check conditions that are known to vary across situations, or conditions that are seen as being more salient and important. In the case of RO-RO ferries, for instance, if the bow port always is closed when the ferry leaves harbour, then there is no need explicitly to verify this condition. And the bow port is always closed, because regulations say that it should be so. Or, to take another example, if a hospital laboratory has routines to ensure that the right type of blood is issued, then it is only necessary to check that the identification of the patient is correct. The nurse has to bring the blood to the right patient, but need not check whether the blood is of the right type.
The net result is that human performance is efficient because people quickly learn to disregard those aspects or conditions that normally are insignificant. This adjustment is furthermore not only a convenient ploy for the individual, but also a necessary condition for the joint system (i.e., people plus other people plus technology) as a whole. Just as individuals adjust their performance to avoid wasting effort, so does the joint system. This creates a functional entanglement, which is essential for understanding why failures occur. The performance adjustment on the joint system level cannot be effective unless the aggregated effects of what individuals do are relatively stable, since this constitutes an important part of the joint system’s environment. On the other hand, the efficient performance of the join system contributes in a significant manner to the regularity of the work environment for the individuals, which is a pre-condition for their performance adjustment.
As far as the level of individual human performance is concerned, the local optimisation – through shortcuts, heuristics, and expectation-driven actions – is the norm rather than the exception. Indeed, normal performance is not that which is prescribed by rules and regulation but rather that which takes place as a result of the adjustments, i.e., the dynamic equilibrium that reflects the regularity of the work environment. This means that we cannot find the cause of failures in the normal actions since they, by definition, are not wrong. This is consistent with the view of complexity theory according to which some properties of the system cannot be attributed to individual components but rather emerge from the whole system.
The conclusion is that both normal performance and failures are emergent phenomena, hence that neither can be attributed to or explained by specific components or parts. For the humans in the system this means in particular that the reason why they sometimes fail, in the sense that the outcome of their actions differ from what was intended or required, is due to the variability of the context and conditions rather than to the failures of actions. The adaptability and flexibility of human work is the reason for its efficiency. At the same time it is also the reason for the failures that occur, although it is never the cause of the failures. Herein lies the paradox of optimal performance at the individual level. If anything is unreasonable, it is the requirement to be both efficient and thorough at the same time – or rather to be thorough when with hindsight it was wrong to be efficient.
© Erik Hollnagel, 2005