The following has been mentioned a paper study (1) published in 2006, four years before Clifford's book was released:
Driver safety and information from afar: An experimental driving
simulator study of wireless vs. in-car information services
Cars have changed from pure transportation devices to fully interactive, voice-based systems. While voice interaction in the car has
previously required on-board processing, the growing speed and ubiquity of wireless technologies now enable interaction with a distant
source. Will the perceived source of the information influence driver safety, responses to the information, and attitudes toward the
computer system and car? A between-participants experimental design (N=40) of computer proximity—in-car vs. wireless—using an
advanced car simulator, found that people’s driving behavior, verbal responsiveness, and attitudes are affected by computer proximity
A combination of real world mishaps and controlled
experimental studies has shown that several factors
significantly affect driver responses to voice interfaces in
cars, including perceived voice gender, emotion, and even age. The BMW 5-series released in Germany included a
voice-based navigational system, featuring a computergenerated
voice with female characteristics. Although these
drivers were well-aware that the voice was computer generated,
they reacted with gender stereotyped responses,
ultimately rejecting the female voice and demanding a
BMW switched the
female voice to a male voice and re-cast the navigational
system voice in the role of a co-pilot.
Finally, you can find the claim in Clifford's book published in 2005:
Wired for speech : how voice activates and advances the human-computer relationship / Clifford Nass and Scott Brave.
And also in this book:
Macneil, R., Cran, W., 2004. Do you speak American? Nan A. Talese.
Both books can be bought from Amazon or Google Books.
1. Driver safety and information from afar: An experimental driving
simulator study of wireless vs. in-car information services. Leila Takayama, Clifford Nass. Department of Communication, Stanford University, Stanford, CA 94305, USA. 2006.