Reply to SL Black

Center for Clinical Pharmacology
School of Medicine
University of Pittsburgh
Pittsburgh, PA

Jian Zhang

Division of Health and Family Studies
Institute for Families in Society
University of South Carolina
Columbia, SC 29208
E-mail: bvw2{at}cdc.gov

Robert E McKeown

Department of Epidemiology and Biostatistics
Arnold School of Public Health
University of South Carolina
Columbia, SC 29208

Dear Sir:

We appreciate Black’s comments and thank him for providing a detailed explanation. It is true that many neuropsychological tests involve timed responses, such that longer response latencies correspond to poorer performance (1). In describing test results, however, there is a tendency to refer to the "speed" of the subject’s response, which is essentially the inverse of response latency. Black’s suggestion that data be scored and reported as the inverse of response latency, corresponding more directly to the concept of speed, is quite appropriate and would have enabled us to avoid confusion among readers (2).

ACKNOWLEDGMENTS

None of the authors had a conflict of interest to declare.

REFERENCES

1. Dye L, Lluch A, Blundell JE. Macronutrients and mental performance. Nutrition 2000;16:1021–34.
2. Zhang J, Muldoon MF, McKeown RE. Serum cholesterol concentrations are associated with visuomotor speed in men: findings from the third National Health and Nutrition Examination Survey, 1988–1994. Am J Clin Nutr 2004;80:291–8.