The answer to the question, "Ability, speed, or both?" may be "both at once" if speed is simply a manifestation of ability. If differences in speed are manifestations of differences in ability, then both speed and ability may reflect a single dimension best characterized by a single score. While measurement of speed has proven utility in research, it remains to be seen whether rate measures (or measures that combine rate and accuracy) can improve professional practice by improving decision-making in job selection, higher education selection, clinical diagnosis, job placement, and educational placement. Studies cited by Frank Goldhammer ("MIRP," v13 n3-4 p133-164 2015) suggest that item time limits are feasible and that test-takers can adjust to such time limits. Goldhammer presents several arguments for the use of item time limits. Davidson states, however, that because of the stakes involved, test publishers will, for good reasons, not want to adopt item time limits without substantial evidence of their contribution. The studies are somewhat difficult to conduct and require substantial real (rather than simulated) data. The required evidence will take time to accumulate. Much of it will come from clinical, counseling, educational, and industrial/ organizational psychology.