'It is generally not convenient to shape skillful behavior with a negative reinforcer because it elicits many respondents which may conflict, be incompatible with the behavior to be shaped' (Holland & Skinner, The Analysis of Behavior, McGraw-Hill 1961, p. 219 § 32-37).
'[T]he greater the severity of the punishment (after some minimum intensity is surpassed), the lower the response rate' (Ibid., p. 269, § 40-39).
'[P]unishment does not actually eliminate behavior from a repertoire, and its temporary achievement is obtained at tremendous cost in reducing the over-all efficiency and happiness of the group' (Skinner, Science and Human Behavior, Macmillan 1953, p. 190.
Piper: Skinner thought punishment was effective for certain purposes.
Let's see the reference.