Methodology III: Empirical Evaluation - Foundations for Designing User-Centered Systems - page 364

providing the developers with a written report of qualitative and quantitative
performance data. They can also be used when the developers are remote from the
site where the evaluation is taking place, as long as suitable network connections
are available to transmit the recordings.
13.5.5 Eye Movement Tracking
In the last 10 years an increasing number of people have begun to collect data on
eye movements to analyze how people use web pages (e.g., Nielsen and Pernice
2010 ; and see Navalpakkam and Churchill in press, for a more general review of
eye-tracking). The current eye-tracking equipment is much easier to use, much
cheaper, and much less invasive than earlier generations of eye-trackers which
required you to have your head clamped in place, and required frequent re-cali-
bration. They also generated large amounts of data that required significant effort
to analyze and interpret, whereas there are now several good software packages
available that will help you make sense of the data. You should recall that we
discussed eye-tracking in Chap. 4 .
Eye movement data is particularly useful as a way of generating heat maps
which show the hot spots on a web page. These are the parts of a web page that
users spend most of their time looking at, either by gazing at it for a long period of
time, or visiting it for several shorter periods of time. In general, users have
predetermined expectations about where they expect certain items such as menus,
navigation bars, back/next buttons, and so on to appear on a web page. This leads
them to automatically look for those items in the expected places first. If they are
not where they are expected to be, you start to see scan patterns in the eye
movements as the eyes jump around trying to find the required element.
There are some drawbacks to using eye movement data, which mean that you
often need to complement it by using an additional method. The two main
drawbacks are that the data do not tell you why users fixated on a particular point
on the page and that the data do not tell you what items on the page the participant
missed or did not notice.
13.5.6 Questionnaires and Surveys
If you want to discover opinions about something, often the best way is to ask
people. Subjective measures are frequently used to assess attitudes towards a new
piece of technology—feelings of control, frustration, etc. Sometimes just asking
people for their opinions is the only way of gathering this data. Note, however, that
sometimes surveys can measure opinions but not actions; early work has shown that
what people do and what they say they will do can vary up to 100% (LaPiere 1934 ).
Surveys are more valid when the attitudes are more stable, relevant, and salient to