ABSTRACT
Even at a time when the beautiful mechanisms of molecular genetics were unknown, Darwin was able to identify several factors that affect variation in phylogenetic evolution. Darwin knew nothing of the genetics that underlie phenotypic variation. The Darwinian metaphor can be applied in many different ways, and there is often no easy way to distinguish empirically among them. What we can say is that Skinner's application was rather superficial. For example, Pavlovian conditioning, which allows a neutral stimulus to acquire signal properties, will itself give rise to a repertoire of reinforcer-related activities on which operant reinforcement can act. Intrinsic to the Darwinian metaphor is the distinction between phenotype and genotype. The phenotype is the visible outcome of the developmental process, the whole organism with its morphology and behaviour. Skinner never accepted the competence-performance distinction. Consequently, he never admitted that the phenotype-genotype distinction might also apply to operant behaviour, even though it is part and parcel of the Darwinian metaphor.
