Technology Acceptance Model for Mobile Services as a Design Framework - Human-Computer Interaction and Innovation in Handheld, Mobile and Wearable Technologies - page 85

especially suitable for field trials where the focus
is on how different users start using the mobile
services in their everyday lives and which features
make the services acceptable in actual usage. As
not all the field study findings could be fit to the
original TAM model, it was necessary to update
the model according to the repeated field study
findings and themes identified in related research.
The new model extends the original core model
by Davis (1989) by identifying two new perceived
product characteristics that affect the intention to
use, i.e. trust and ease of adoption, and by redefin-
ing the theme of usefulness as value to the user.
The framework (Figure 4) suggests that per-
ceived ease of use, perceived value and trust affect
the intention to use a mobile service. To get 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.
The Technology Acceptance Model for Mobile
Services (Kaasinen, 2005b) constitutes a frame-
work that helps designers of mobile services to
identify key issues that should be focused on in

the design to ensure user acceptance. Thus the
motivation of the model is not the same as the
motivation of the original TAM, which was built
to explain user acceptance and underlying forces
for existing technical solutions.
Perceived ease of use was included in the
original TAM and it is also included in the TAMM
model. Davis (1989) defined perceived ease of
use as “ the degree to which a person believes
that using a particular system would be free from
effort ”. At first, perceived ease of use is based
on external factors such as the user's attitude
towards technology in general, experiences of
using similar services and information from other
people. In actual use and sustained use, perceived
ease of use is increasingly affected by the user's
own experiences of using the system in different
contexts of use.
In the case of mobile services that are used on
small devices such as mobile phones or PDAs, the
limitations of the device have a major influence on
perceived ease of use. The limitations include the
small screen, small and limited keyboard, the ab-
sence or limited functionality of pointing devices,
limited amount of memory, limited battery power
and slow connections. As new devices and mobile

Figure 4. Technology acceptance model for mobile services (Kaasinen, 2005b) as an extension and
modification of TAM by Davis (1989).