A modern approach to the testing of graphical symbols

Graphical symbols have the potential benefit of communicating to people who are unable to understand a written language, a situation facing more and more people as international travel and trade increases. But this benefit is only achieved if the symbols communicate the intended meaning; if viewers interpreted a symbol as having a meaning the opposite to that intended, there could be disastrous consequences. The International Standards Organization (ISO) through its Technical Committee 145 is involved in developing internationally agreed symbols, the aim being to promote consistency and reduce the likelihood of misunderstanding. Two aspects of the effort to achieve this aim are first demonstrating that symbols communicate the intended message and second that where there are alternative designs for a symbol the one which is used is the one which has been demonstrated to communicate the message to the greater proportion of people. A number of procedures for testing symbols have been devised and applied over many years. There has been debate over which method best meets the technical requirements of validity and reliability and the practical requirements of being simple and inexpensive to apply. There has also been debate over the extent to which these two sets of requirements are compatible. ISO has developed its own standard (ISO 9186) for testing graphical symbols. In this chapter, the main features of the different parts of ISO 9186 are explained and some research using the standard is described. Although the subjective component of evaluating symbols is lessened by adopting a standard test procedure, judgements of whether a response shows a correct understanding of the symbol are still required. It is important that these should be reliable, meaning that different judges are consistent with each other. Examples are cited of the problems which can arise and of the way they can be resolved.