Exotic mice for aging: authors' reply

The authors reply here to comments made by Drs. McClearn and Festing about the strengths and weaknesses of nonstandard mouse models in experimental ge rontology, stressing once again the trade-off between internal and external validity. Although the use of genetically isogenic mice may, in some cases , minimize experimental costs by diminishing variance among individuals, re liance on a small number of inbred, long-domesticated stocks diminishes the external validity of a research program, i.e., the degree to which its con clusions give insights into questions of greater biological interest than t he behavior of a single genotype. (C) 1999 Elsevier Science Inc. All rights reserved.