Stein, K. B. (1961). The effect of brain damage upon speed, accuracy, and improvement in visual motor functioning. Journal of Consulting Psychology, 25(2), 171-177.
http://dx.doi.org/10.1037/h0045286
Speed, accuracy, and improvement in a substitution task are fairly independent and are all impaired in a brain-injured group. Age is related to all 3 variables. From Psyc Abstracts 36:04:4JG71S. (PsycINFO Database Record (c) 2016 APA, all rights reserved)