We investigated strong-verb paradigm leveling in German, Dutch, English, and Swedish, and found significant differences in ablaut leveling and class change towards the weak conjugation. Swedish favors ablaut patterns retaining a difference between the preterite and the past participle, while German, Dutch, and English favor a common vowel for both forms. In change from the strong to the weak conjugation in Swedish, the preterite is more resistant than the past participle, while in the other languages it is the reverse. We provide a unified explanation for these facts based on differences in category frequency due to the prominence or lack of an aspectual distinction between preterite and perfect