Increasing the generalizability (or external validity) of a model. This can be achieved by assessing the effects of rearing and housing conditions (first column) through partial, systematic, and conceptual replications (see Fig. 1). Gender effects (second column), ontogenetic and aging effects (third column) should be an integral part of the model building process. In addition, the battery of tests for assessing the dependent variables (see Table 1, Part B, second and third column) should be extended and should include tests that are believed to measures the same trait/construct (fourth column; e.g. the Barnes maze , the T-maze , and the Morris maze  may be used to assess spatial working memory performance). Quasireplications are not part of the model building process, but may be used for assessing the generalizability across species.