The standard of pleasure is fixed in the womb. Contextual, stored data consists of warmth, softness, quiet. etc.. If the womb were constructed of sharp objects what is called pain would be the standard of pleasure. But if this were so the fetus would be torn apart. The standard of pleasure is as it is out of logical necessity.
Pain is then a deviation from the acquired context.
The sensation of pleasure cannot be separated from the sensation of pain. If nothing is compared to the standard and found to be in opposition, that standard is not experienced as pleasure. It would be experienced simply as the unacknowledged 'normal' contextual state. What a sensation is, is equally dependent on what it is not. The standard of pleasure is therefore validated by comparison to pain. The initial incidence of validation is birth trauma, i.e. the introduction of an excessive non-contextual differential (one which cannot be described as 'contextual variation').
The primary standard is pleasure while the experience of pain forms a secondary standard. That standard most reinforced is the preferred form (prlmary) of experience to the individual entity. Thus, an individual may seek pain in the exceptional case but such 'deviant' behavior is inconsistent with the maintenance of life.