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measure of their experience, but it might offer an additional set of data points
and potentially insight into causes of stress in their experience.
7.4.2 Heart Rate Variance and Skin Conductance Research
Several studies have sought to determine whether skin conductivity and heart
rate could be used as indicators of stress or other adverse reactions in a usabil-
ity setting. For example, Ward and Marsden (2003) used skin conductance and
heart rate to measure user reactions to two
versions of a website: a well-designed ver-
sion and a poorly designed version. The
poorly designed version included exten-
sive use of drop-down lists on the homep-
age to “hide” much of the functionality,
provided impoverished navigational cues,
used gratuitous animation, and had occa-
sional pop-up windows containing ads.
Heart rate and skin conductance data were
plotted as changes from the participant's
baseline data established during the first
minute of the session.
Both measures showed a decrease in
heart rate and skin conductance for the well-
designed website. For the poorly designed
site, skin conductance data showed an
increase over the first 5 minutes of the ses-
sion, followed by a return to baseline over
the final 5 minutes. Heart rate data for the
poorly designed version showed some vari-
ability, but the overall trend was to stay at
the same level as the baseline, unlike the
well-designed version, which showed a decrease relative to baseline. Both mea-
sures appear to reflect greater stress in interacting with the poorly designed site.
Figure 7.19 Data showing the heart rate of participants as they
experienced different levels of response time waiting for web pages
to load. Wait times of 10 and 22 seconds yielded progressively greater
increases in heart rate relative to baseline, indicating physiological stress.
Adapted from Trimmel et al. (2003) used with permission.
Trimmel, Meixner-Pendleton, and Haring (2003) measured skin conductance
and heart rate to assess the level of stress induced by the response times for web
pages to load. They artificially manipulated page load times to be 2, 10, or 22 sec-
onds. They found significant increases in heart rate as response time (page load
time) increased, as shown in
Figure 7.19
. A similar pattern was found for skin con-
ductance. This is evidence of physiological stress associated with longer response
times.
7.4.3 Other Measures
A few creative researchers have come up with some other techniques that might
be appropriate for assessing the user's level of frustration or engagement while
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