## Appendix A The Subjective Assessment of Speech System Interfaces Questionnaire (SASSI)  
This appendix shows the SASSI questionnaire given to the subjects of both user studies. Each question consists of a 6-point Likert scale, where 1 stands for _Strongly disagree_ and 6 to _Strongly agree_.  
As described in Section 5, extra questions were added in each user study to evaluate some areas that were not covered by SASSI. Some of these questions were extracted from other questionnaires (_Verbosity_ and _Productivity_, from the SUISQ [43] questionnaire) and others were manually created (_Security_). So as to be integrated into the original SASSI questions, these extra questions were also evaluated by using a 6-point Likert scale.  
It is important to note that the statements in SASSI can have positive (\"The system is accurate\") or negative (\"I felt tense using the system\") connotations. So as to obtain consistent evaluations, it is necessary to rescale negative statements so as to be considered as positive. For example, if a negative statement has a score of 1, its rescaled score would be 6 [44].  
For understandability reasons, the questions in this appendix are in English. However, a Spanish version, translated by an expert, was provided to the study subjects.  
\begin{tabular}{l l} \hline \hline  & **Response Accuracy** \\ \hline
1. & The system is accurate. \\
2. & The system is unreliable. \\
3. & The interaction with the system is unpredictable. \\
4. & The system didn't always do what I wanted. \\
5. & The system didn't always do what I expected. \\
6. & The system is dependable. \\
7. & The system makes few errors. \\
8. & The interaction with the system is consistent. \\
9. & The interaction with the system is efficient. \\ \hline  & **Likeability** \\ \hline
10. & The system is useful. \\
11. & The system is pleasant. \\
12. & The system is friendly. \\
13. & I was able to recover easily from errors. \\
14. & I enjoyed using the system. \\
15. & It is clear how to speak to the system. \\
16. & It is easy to learn to use the system. \\
17. & I would use this system. \\
18. & I felt in control of the interaction with the system. \\ \hline  & **Cognitive Demand** \\ \hline
19. & I felt confident using the system. \\
20. & I felt tense using the system. \\
21. & I felt calm using the system. \\
22. & A high level of concentration is required when using the system. \\
23. & The system is easy to use. \\ \hline  & **Annoyance** \\ \hline
24. & The interaction with the system is repetitive. \\
25. & The interaction with the system is boring. \\
26. & The interaction with the system is irritating. \\
27. & The interaction with the system is frustrating. \\
28. & The system is too inflexible. \\ \hline  & **Habitability** \\ \hline
29. & I sometimes wondered if I was using the right word. \\
30. & I always knew what to say to the system. \\
31. & I was not always sure what the system was doing. \\
32. & It is easy to lose track of where you are in an interaction with the system. \\ \hline  & **Speed** \\ \hline
33. & The interaction with the system is fast. \\
34. & The system responds too slowly. \\ \hline  & **Extra: Verbosity--both UCs** \\ \hline
35. & I felt like I had to wait too long for the system to stop talking so I could respond. \\ \hline \hline \end{tabular}