In complex products, regardless of the scale of their production (small runs or large series), ergonomic design research sets out to cater for the new demands of interdisciplinarity of approach and in particular seems to have become indispensable for developing high-risk objects with a high degree of technological content, i.e. those objects that call for such massive investments that the risk of failure must be reduced to a minimum, or those objects in which the system is so critical that even the slightest lack of correspondence between man and machine may cause damage out of all proportion to the scale of the anomalous event that produced it. Malfunctions are notoriously often caused by ‘misunderstandings’ between a technological system and the humans who govern it. Many of the accidents that are attributed to ‘human error’ are actually brought about by such ‘misunderstandings’ that occur when people react instinctively to an unexpected event or a particularly stressful situation in ways that deviate from the models they have learned. Many accidents, even the most disastrous ones, can be traced back to such misunderstandings between man and machine, to inadequate legibility or comprehensibility of signals and messages or to the difficulty involved in learning or remembering the correct procedures to be followed.