Abstract
If selection is interpreted as involving repeated cycles of replication, variation, and environmental interaction so structured that environmental interaction causes replication to be differential, then selection in gene-based biological evolution and the reaction of the immune system to antigens are relatively unproblematic examples of selection processes. Operant learning and cultural evolution pose more serious problems. In this response we deal with operant learning as a selection process. Footnotes1 The authors regretfully inform readers that since the publication of our target article in 2001, one of our coauthors, Rod Langman, has died.