Peterson, J., & Allison, L. W. (1931). Controls of the eye-wink mechanism. Journal of Experimental Psychology, 14(2), 144-154.
http://dx.doi.org/10.1037/h0070197
Rates of voluntary blinks were found to be consistent and individually characteristic at a mean of about 3.7 winks per sec. The winks can be self-counted. The authors believe the wink mechanism is a good one for experiments on voluntary controls, set, etc. (PsycINFO Database Record (c) 2016 APA, all rights reserved)