Davis presented, in 1989, the Technology Acceptance Model (TAM) to explain the determinants of user acceptance of a wide range of end-user computing technologies (Davis 1989). TAM points out that perceived ease of use and perceived usefulness affect the intention to use. Davis (1989) defines perceived ease of use as "the degree to which a person believes that using a particular system would be free from effort" and perceived usefulness as "the degree to which a person believes that using a particular system would enhance his or her job performance". Perceived ease of use also affects the perceived usefulness. The intention to use affects real usage behaviour.

TAM was originally developed for studying technology at work. Later it has been used as such or modified to study user acceptance of consumer services such as Internet services or e-commerce (Kaasinen, 2005). The Technology Acceptance Model constitutes a solid framework for identifying issues that may affect user acceptance of technical solutions. As Davis and Venkatesh (2004) have proved, the model can be enhanced from the original purpose of studying user acceptance of existing products to study planned product concepts, e.g. in the form of mock-ups. This indicates that TAM could also be used in connection with technology development projects and processes to assess the usefulness of proposed solutions. Applied in this way, the model also supports the human-centred design approach.

VTT has adopted TAM in connection with field trials carried out in connection with the research and development of new technology. When field trials are included in the design process, the focus of usability studies is enhanced from the traditional usability conception of specified users performing specified tasks in specified contexts of use. In field trials, users can use the prototype services as part of their everyday life. The research framework can then be enhanced to identify the actual tasks that users want to perform and the actual contexts of use. Technology acceptance models provide a framework for these kinds of studies.

VTT has modified the original TAM based on studies of mobile consumer services. Technology Acceptance Model for Mobile Services (Kaasinen, 2005) suggests that perceived ease of use, perceived value and trust affect the intention to use a mobile service. To move from an intention to use to real usage, the user has to take the service into use. This transition is affected by the perceived ease of adoption. Perceived value, perceived ease of use, trust and perceived ease of adoption need to be studied in order to assess user acceptance of mobile services.

Davis F. D. 1989. Perceived usefulness, perceived ease of use, and user acceptance of information technology. MIS Quartely:13/1989, pp. 319–339.

Davis, F. D. and Venkatesh, V. 2004. Toward preprototype user acceptance testing of new information systems: implications for software project management. IEEE Transactions on Engineering Management, Vol. 51, No 1.

Kaasinen, Eija. 2005 . User acceptance of mobile services - value, ease of use, trust and ease of adoption. (/) VTT Information Technology, Espoo. 151 s. VTT Publications 566. ISBN 951-38-6640-8. 951-38-6641-6