(The Graduate University for Advanced Studies, School of Cultural and Social Studies,
Long Term Usability, Usability, ISO 9241-11, Context of Use, Time-Line Interview, Chronology of Product Use
"Usability" is a concept of the ease of use or the ease of operation for products and services. Until now, products and services are evaluated at a specific point in early stage of use. However, people use products and services for long time and the evaluation for them usually varies during that period. The purpose of my work was to examine a determination of “Long Term Usability” which was made an addition to the transition of time in present concept of usability.
In this paper, I investigated long term products and services use in actual environment with interview method of making “chronology of product use”. The interview method of making chronology of product use is modified Time-Line Interview in information behavior field. In this research I asked 14 persons their histories of use and their evaluation changes for products and services after long term uses. Target products and services were 45 objects that the informants had choice by themselves.
As a result, the factor of actual feeling for long time product or service use did not correlate with physical time length. It tended to have high-relation with subjective frequency and habituation. Also it was found that there were 2 typical patterns of evaluation change during long time use. First is a pattern of evaluation change by the transition of user's context of use. Second is the evaluation change because users realize latent functionality which is not found out in usual operation at first. These two patterns accounted for 82% of the whole.
At the first pattern, the users experienced quite big changes of their lifestyles or environments. For example he/she became a university student, became busy at the office etc. The transition of user's context of use brings their changes of uses of the products and services. Thus, they realize needs for a new functionality. That is why evaluation changes. Based on these research results, the life cycle model for Long Term Usability was examined.