Stimuli were all possible patterns of 10 lights. Responses were corresponding patterns of simultaneous key depressions in a 10-key keyboard, (1 key for each finger). After more than 75,000 discrimination reaction times (DRTs) for each of 3 Ss, average DRT under the 1023-alternative condition exceeds that under a 31-alternative condition by less than 25 msec. DRT does not increase linearly with information transmitted. Learning curves for the 1023-alternative task are described by: Ý = (A) (X + E)-super(B)B + C. Idiosyncratic and relatively long-term performance shifts limit the precision of fit. r-super(2) alone was not an adequate criterion of goodness of fit. (16 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved)