Behavioral and Physiological Metrics - Measuring the User Experience: Collecting, Analyzing, and Presenting Usability Metrics - page 178

in online panels and in usability labs. Affdex facial-expression recognition pro-
vides an indication of the type of experience associated with the state of arousal.

Facial expressions are captured through a standard web camera on the par-
ticipant'scomputerandtimesynchronizedwithdatafromtheQSensor.This
provides a rich data set, as peaks in arousal can be associated with a positive or
negative valence. With Affdex, Affectiva is building the largest database of spon-
taneously generated facial expressions in the world. This will allow Affectiva
to develop more advanced classifiers of different emotions, which will be
used to predict increases in sales or brand loyalty. This powerful technology
will arm the UX researcher with an additional set of tools to better understand
emotional engagement across a wide variety of experiences. Case study 10.5
highlightsuseoftheQSensorinthecontextofusinganonscreenandtablet-
based textbook.

RELATIONSHIP AMONG TASK PERFORMANCE, SUBJECTIVE
RATINGS, AND SKIN CONDUCTANCE

In a study of participants playing a 3D video game (Super Mario 64), Lin, Hu, Omata,
and Imamiya (2005) looked at the relationships among task performance, subjective
ratings of stress, and skin conductance. Tasks involved playing three different parts of
the game as quickly and accurately as possible. Participants played each part (task) for
10 minutes, during which period they could potentially complete the goal (succeed)
multiple times. There was a strong correlation between participants' ratings of how
stressful each of the tasks was and their normalized skin conductance (change relative to
the participant's baseline) during the performance of each task. In addition, participants
who had more successes during the performance of each task tended to have lower skin
conductance levels, indicating that failure was associated with higher levels of stress
(see Figure 7.13 ).

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Task 1 ask 2 ask 3
(b)
Figure 7.13 Data showing subjective ratings of stress (a) and normalized skin conductance (b) for
three different tasks in a video game. Both show that Task 3 was the most stressful, followed by
Task 2 and then Task 1. Adapted from Lin et al. (2005).

Task 1 ask 2 ask 3
(a)