At the clinic in Cavalia we had wonderful discussions about why pressure is not aversive even though it falls in to the operant conditioning category of +P.
“Pressure in itself is not an aversive, it is a predictor (cue or Sd) for what is to come. Think about a hug; it can be a tight long hug from someone, but if that is a best friend then it’s not aversive, it’s actually pleasant.”
Pressure is just a cue. How you set it up will determine whether it is aversive or not.
Cues are not what we like or dislike, what they predict is what we like or dislike. Cues are really just a predictor of outcomes and pressure in itself is not aversive unless the outcome predictably makes it aversive. If the pressure cue is set up in such a way that the outcome is pleasant the pressure cue is sought by the learner.
+P is not aversive. +P is just maths. How you set it up determines whether it is aversive or pleasant for the learner.