144 10th-grade Ss learned verbal paired associates in a factorial design with 4 list lengths (4, 8, 12, and 20 pairs), 3 levels of meaningfulness, 3 rates of presentation (3, 4, and 8 sec.), 2 levels of ability, and 2 equivalent forms. Dependent variable was amount of time to learn each pair to 1 correct anticipation, summed over the pairs in a list; logarithms of these measures were used. All main effects except list form were significant. For the 9 combinations of Meaningfulness X Rate of Presentation, the regressions of log-sub(e) learning times on log-sub(e) list length did not depart significantly from linearity; they had a common slope but significantly different intercepts, in agreement with Thurstone's rational equation stating that learning time increases as the 3/2 power of list length. (PsycINFO Database Record (c) 2006 APA, all rights reserved)