Matt Jones found this little nugget in the Feburary 2003 Journal of Personality and Social Psychology:
The Minority Slowness Effect: Subtle Inhibitions in the Expression of Views Not Shared by Others
Five studies revealed that people who hold the minority opinion express that opinion less quickly than people who hold the majority opinion. The difference in speed in the expression of the minority and majority opinions grew as the difference in the size of the minority and majority grew. Also those with the minority view were particularly slow when they assumed the majority to be large whereas the opposite was true for those with the majority view. The minority slowness effect was not found to be linked to attitude strength, nor was it influenced by anticipated public disclosure of the attitude.
via David Smith