Behavioral and Physiological Metrics - Measuring the User Experience: Collecting, Analyzing, and Presenting Usability Metrics - page 184

Figure 7.20 The PressureMouse is an experimental mouse that can detect how tightly the user is
gripping it. The plastic overlay (a) transmits pressure to six sensors on the top and sides of the mouse (b).
As users become frustrated with an interface, many of them subconsciously grip the mouse tighter. The
pressure-sensitive mouse was developed by Carson Reynolds and Rosalind Picard of the MIT Media Lab.
interacting with a computer. Most notably, Rosalind Picard and her team in the
Affective Computing Research Group at the MIT Media Lab have investigated
a variety of techniques for assessing the user's emotional state during human-
computer interaction. Two of these techniques that might have application to
usability testing are the PressureMouse and the Posture Analysis Seat.
The PressureMouse (Reynolds, 2005), shown in Figure 7.20 , is a computer
mouse with six pressure sensors that detect how tightly the user is gripping the
mouse. Researchers had users of the PressureMouse fill out a five-page web-based
survey (Dennerlein et al., 2003). After submitting one of the pages, participants
were given an error message indicating that something was wrong with their entries
on that page. After acknowledging the error message, participants were then taken
back to that page, but all the data they had entered had been deleted and they had
to reenter it. As illustrated in Figure 7.21 , participants who had been categorized as
members of a “high-response” group (based on their negative ratings in a usability
questionnaire about the online survey) gripped the mouse significantly tighter for
the 15 seconds after their loss of data than they did for the 15 seconds before.
The Posture Analysis Seat measures the pressure that the user is exerting on
the seat and back of the chair. Kapoor, Mota, and Picard (2001) found that they
could reliably detect changes in posture on the part of the participant, such as sit-
ting upright, leaning forward, slumping backward, or leaning sideways. These may
be used to infer different levels of engagement or interest on the part of the par-
ticipant. Of course, anyone who has taught can easily see a student's engagement
basedonhowmuchtheyslouchintheirseat!
These new technologies have yet to be used in everyday usability testing, but
they look promising. As these or other technologies for measuring engagement
or frustration become both affordable and unobtrusive, they can be used in
many situations in which they could provide valuable metrics, such as design-
ing products for children who have limited attention spans, evaluating users'