In psycholinguistics, Clark and Clark (1977, p. 538 ff.; see also Clark, 1969) reported that one of the most common universals found in language is that negatives (in the sense of negation, not evaluation) are marked in contrast to positives (in the sense of presence, not evaluation), and hence, negatives are more complex (for example, “John is there” vs. “John is not there”). Furthermore, they also noted that it is possible to express bad (in the sense of evaluation) negatively or positively; good, on the other hand, is always expressed positively. For example, you can either be unhappy or sad, but if you are happy, you are not unsad (Greenberg, 1966). Clark and Clark (1977) explained this asymmetry with the notion of normality:

Normal states are conceived of positively, and abnormal states as the absence of normal states, as negative states. . . .Note that milk in its ordinary state is “good milk,” but milk in its abnormal state has “gone bad.” Goodness is considered normal because it is what is expected— what should be—and so badness is abnormal. (p. 539)

Thus, positivity is assumed to be the norm, while negativity is a deviation from this norm.

Unkelbach C. и др. Why positive information is processed faster: the density hypothesis. // Journal of personality and social psychology. 2008. Т. 95. № 1. С. 36-49.

Никогда не думал об этом в таком ключе. Хотя вроде есть и исключения, в русском по крайней мере: незлой, нестрашный. Впрочем, они нейтральные, а не позитивные.