Deviant intervals were always four semitones and thus the difference was always 1-3 semitones

Evidence

Since standard pattern intervals were chosen from the set {1, 2, 3, 5, 6, 7 semitones}, depending on the condition (see Table 1 ), the difference between the standard and the deviant pitch interval was always 1, 2 or 3 semitones. — Dijk, Pim van, Physiology, Psychoacoustics and…, 5298