 As we discussed in Section 1, for more than 150 years there has been disagreement over how to define instinctive (or innate) traits in a way that is useful to scientific psychology. Shortly after instinct had become a topic of scientific study, C.L. Morgan (1896) identified seven “definitional” issues surrounding this term. Two decades later, criticisms by Knight Dunlap (1919) and L.L. Bernard (1921) reveal that those ambiguities had not been resolved. It is also telling that Lorenz continued to modify his definition of innateness in response to critics over the course of his career, while Tinbergen eventually abandoned this term altogether. More recently, behavioral biologist Patrick Bateson has observed that, “[a]t least six meanings are attached to the term [innate]: present at birth; a behavioral difference caused by a genetic difference; adapted over the course of evolution; unchanging throughout development; shared by all members of a species; and not learned” (1991, 21). His objection is not merely that the term “innate” is ambiguous. Like Dunlap (1919) and Bernard (1921), his complaint is that ambiguity promotes equivocation, encouraging researchers to draw faulty inferences as they slide between different senses of innateness. For example, if a trait is deemed “innate” because there is evidence that it is present at birth, psychologists will sometimes infer (without further evidence) that it is therefore “innate” in the sense of being insensitive to environmental influence. Developmental biologists since Kuo (1921) have provided evidence against this easy inference. Bateson’s own work on the phenomenon of parental imprinting in birds (Bateson, 1966) showed that traits which appear early in life are often highly sensitive to specific environmental factors. The tendency for nativism to promote such unwarranted inferences has been one of the main reasons why many scientists have called for dramatic revision or even an elimination of this concept from scientific discourse (see Section 4.5 of this entry).