(part 3 of 4)
Ergonomics is not only highlighting these problems but GENERALISING from them to predict other situations where they might occur and where difficulties can be prevented.
Consideration of these issues in the context of the tasks the users are to perform leads to the development of
GUIDELINES, and
These offer recommendations for how to design or redesign an object. They are concerned with designing objects that take account of the capabilities for the human user, including anthropometric (and physiological and biomechanic), behavioural, and cognitive constraints. They are fairly general so offer little in the way of specific design advice.
Many standards, guidelines and principles are derived from lab-based research. As such, they may be impractical in some situations as they ignore potentially crucial situation-specific and context related information, which affects the way in which a tool is used. However, they do serve to narrow the space of design options by enabling broad predictions of usability at the drawing board stage.
Standards tend to be concerned with human adaptability and human variability. They are prescriptions for "safe", acceptable designs, detailing the limits outside which the user may suffer from stress and 'accidents' may be caused. They are primarily concerned with enforcing legality. For example, BS 5330 deals with the relationship between sound levels to which people are exposed in a working day and incidence of hearing loss.
Guidelines are predictive and offer some general guidelines for making design decisions. They tend to be more specific than principles, but still relate existing theory and knowledge to either new design or established design problems.
Principles: are again predictive and specify principles which can underpin design decisions. They do not specify the limits of human capabilities like standards do and tend to be more general than guidelines. (Note that although we make this distinction between guidelines and principles, the literature on ergonomics does not in general). Ideally, such principles are theoretically motivated.
Norman (1988) outlines a set of principles that designers could consider when designing. For example, making things visible and providing feedback. Norman's principles are based on his theory of action (and interaction).
The issue of principles rather than multiple single examples. How can we differentiate principles from guidelines and standards?
Visibility, feedback, understanding, consistency.